Add annotations to the Lint API

Change-Id: I6222f3ef2909174d9111dcfc037a2e74ad093acd

27 files changed, 542 insertions, 230 deletions

diff --git a/lint/libs/lint_api/src/com/android/tools/lint/client/api/Configuration.java b/lint/libs/lint_api/src/com/android/tools/lint/client/api/Configuration.java
index 461c438..8f5f230 100644
--- a/lint/libs/lint_api/src/com/android/tools/lint/client/api/Configuration.java
+++ b/lint/libs/lint_api/src/com/android/tools/lint/client/api/Configuration.java
@@ -16,6 +16,8 @@
 
 package com.android.tools.lint.client.api;
 
+import com.android.annotations.NonNull;
+import com.android.annotations.Nullable;
 import com.android.tools.lint.detector.api.Context;
 import com.android.tools.lint.detector.api.Issue;
 import com.android.tools.lint.detector.api.Location;
@@ -46,8 +48,12 @@ public abstract class Configuration {
      *            more information
      * @return true if this issue should be suppressed
      */
-    public boolean isIgnored(Context context, Issue issue, Location location,
-            String message, Object data) {
+    public boolean isIgnored(
+            @NonNull Context context,
+            @NonNull Issue issue,
+            @Nullable Location location,
+            @NonNull String message,
+            @Nullable Object data) {
         return false;
     }
 
@@ -58,7 +64,7 @@ public abstract class Configuration {
      * @param issue the issue to check
      * @return false if the issue has been disabled
      */
-    public boolean isEnabled(Issue issue) {
+    public boolean isEnabled(@NonNull Issue issue) {
         return getSeverity(issue) != Severity.IGNORE;
     }
 
@@ -70,7 +76,7 @@ public abstract class Configuration {
      * @param issue the issue to look up the severity from
      * @return the severity use for issues for the given detector
      */
-    public Severity getSeverity(Issue issue) {
+    public Severity getSeverity(@NonNull Issue issue) {
         return issue.getDefaultSeverity();
     }
 
@@ -81,12 +87,16 @@ public abstract class Configuration {
      *
      * @param context The scanning context
      * @param issue the issue to be ignored
-     * @param location The location to ignore the warning at
+     * @param location The location to ignore the warning at, if any
      * @param message The message for the warning
      * @param data The corresponding data, or null
      */
-    public abstract void ignore(Context context, Issue issue, Location location,
-            String message, Object data);
+    public abstract void ignore(
+            @NonNull Context context,
+            @NonNull Issue issue,
+            @Nullable Location location,
+            @NonNull String message,
+            @Nullable Object data);
 
     /**
      * Sets the severity to be used for this issue.
@@ -95,7 +105,7 @@ public abstract class Configuration {
      * @param severity the severity to associate with this issue, or null to
      *            reset the severity to the default
      */
-    public abstract void setSeverity(Issue issue, Severity severity);
+    public abstract void setSeverity(@NonNull Issue issue, @Nullable Severity severity);
 
     // Bulk editing support
 
diff --git a/lint/libs/lint_api/src/com/android/tools/lint/client/api/DefaultConfiguration.java b/lint/libs/lint_api/src/com/android/tools/lint/client/api/DefaultConfiguration.java
index 3622a73..1281987 100644
--- a/lint/libs/lint_api/src/com/android/tools/lint/client/api/DefaultConfiguration.java
+++ b/lint/libs/lint_api/src/com/android/tools/lint/client/api/DefaultConfiguration.java
@@ -16,6 +16,8 @@
 
 package com.android.tools.lint.client.api;
 
+import com.android.annotations.NonNull;
+import com.android.annotations.Nullable;
 import com.android.tools.lint.detector.api.Context;
 import com.android.tools.lint.detector.api.Issue;
 import com.android.tools.lint.detector.api.Location;
@@ -62,10 +64,15 @@ public class DefaultConfiguration extends Configuration {
     private static final String CONFIG_FILE_NAME = "lint.xml"; //$NON-NLS-1$
 
     // Lint XML File
+    @NonNull
     private static final String TAG_ISSUE = "issue"; //$NON-NLS-1$
+    @NonNull
     private static final String ATTR_ID = "id"; //$NON-NLS-1$
+    @NonNull
     private static final String ATTR_SEVERITY = "severity"; //$NON-NLS-1$
+    @NonNull
     private static final String ATTR_PATH = "path"; //$NON-NLS-1$
+    @NonNull
     private static final String TAG_IGNORE = "ignore"; //$NON-NLS-1$
 
     private final Configuration mParent;
@@ -81,15 +88,21 @@ public class DefaultConfiguration extends Configuration {
      */
     private Map<String, Severity> mSeverity;
 
-    protected DefaultConfiguration(LintClient client, Project project, Configuration parent,
-            File configFile) {
+    protected DefaultConfiguration(
+            @NonNull LintClient client,
+            @Nullable Project project,
+            @Nullable Configuration parent,
+            @NonNull File configFile) {
         mClient = client;
         mProject = project;
         mParent = parent;
         mConfigFile = configFile;
     }
 
-    protected DefaultConfiguration(LintClient client, Project project, Configuration parent) {
+    protected DefaultConfiguration(
+            @NonNull LintClient client,
+            @Nullable Project project,
+            @Nullable Configuration parent) {
         this(client, project, parent, new File(project.getDir(), CONFIG_FILE_NAME));
     }
 
@@ -101,8 +114,11 @@ public class DefaultConfiguration extends Configuration {
      * @param parent the parent/fallback configuration or null
      * @return a new configuration
      */
-    public static DefaultConfiguration create(LintClient client, Project project,
-            Configuration parent) {
+    @NonNull
+    public static DefaultConfiguration create(
+            @NonNull LintClient client,
+            @NonNull Project project,
+            @Nullable Configuration parent) {
         return new DefaultConfiguration(client, project, parent);
     }
 
@@ -115,13 +131,18 @@ public class DefaultConfiguration extends Configuration {
      * @param lintFile the lint file containing the configuration
      * @return a new configuration
      */
-    public static DefaultConfiguration create(LintClient client, File lintFile) {
+    @NonNull
+    public static DefaultConfiguration create(@NonNull LintClient client, @NonNull File lintFile) {
         return new DefaultConfiguration(client, null /*project*/, null /*parent*/, lintFile);
     }
 
     @Override
-    public boolean isIgnored(Context context, Issue issue, Location location, String message,
-            Object data) {
+    public boolean isIgnored(
+            @NonNull Context context,
+            @NonNull Issue issue,
+            @Nullable Location location,
+            @NonNull String message,
+            @Nullable Object data) {
         ensureInitialized();
 
         String id = issue.getId();
@@ -143,7 +164,8 @@ public class DefaultConfiguration extends Configuration {
         return false;
     }
 
-    protected Severity getDefaultSeverity(Issue issue) {
+    @NonNull
+    protected Severity getDefaultSeverity(@NonNull Issue issue) {
         if (!issue.isEnabledByDefault()) {
             return Severity.IGNORE;
         }
@@ -152,7 +174,8 @@ public class DefaultConfiguration extends Configuration {
     }
 
     @Override
-    public Severity getSeverity(Issue issue) {
+    @NonNull
+    public Severity getSeverity(@NonNull Issue issue) {
         ensureInitialized();
 
         Severity severity = mSeverity.get(issue.getId());
@@ -328,7 +351,8 @@ public class DefaultConfiguration extends Configuration {
         }
     }
 
-    private static void writeAttribute(Writer writer, String name, String value)
+    private static void writeAttribute(
+            @NonNull Writer writer, @NonNull String name, @NonNull String value)
             throws IOException {
         writer.write(' ');
         writer.write(name);
@@ -339,8 +363,12 @@ public class DefaultConfiguration extends Configuration {
     }
 
     @Override
-    public void ignore(Context context, Issue issue, Location location, String message,
-            Object data) {
+    public void ignore(
+            @NonNull Context context,
+            @NonNull Issue issue,
+            @Nullable Location location,
+            @NonNull String message,
+            @Nullable Object data) {
         // This configuration only supports suppressing warnings on a per-file basis
         if (location != null) {
             ignore(issue, location.getFile());
@@ -353,7 +381,7 @@ public class DefaultConfiguration extends Configuration {
      * @param issue the issue to be ignored in the given file
      * @param file the file to ignore the issue in
      */
-    public void ignore(Issue issue, File file) {
+    public void ignore(@NonNull Issue issue, @NonNull File file) {
         ensureInitialized();
 
         String path = mProject != null ? mProject.getRelativePath(file) : file.getPath();
@@ -374,7 +402,7 @@ public class DefaultConfiguration extends Configuration {
     }
 
     @Override
-    public void setSeverity(Issue issue, Severity severity) {
+    public void setSeverity(@NonNull Issue issue, @Nullable Severity severity) {
         ensureInitialized();
 
         String id = issue.getId();
diff --git a/lint/libs/lint_api/src/com/android/tools/lint/client/api/DefaultSdkInfo.java b/lint/libs/lint_api/src/com/android/tools/lint/client/api/DefaultSdkInfo.java
index 0392a6f..d012d67 100644
--- a/lint/libs/lint_api/src/com/android/tools/lint/client/api/DefaultSdkInfo.java
+++ b/lint/libs/lint_api/src/com/android/tools/lint/client/api/DefaultSdkInfo.java
@@ -56,6 +56,8 @@ import static com.android.tools.lint.detector.api.LintConstants.VIEW_STUB;
 import static com.android.tools.lint.detector.api.LintConstants.VIEW_SWITCHER;
 import static com.android.tools.lint.detector.api.LintConstants.WIDGET_PKG_PREFIX;
 
+import com.android.annotations.NonNull;
+import com.android.annotations.Nullable;
 import com.google.common.annotations.Beta;
 
 import java.util.HashMap;
@@ -70,12 +72,14 @@ import java.util.Map;
 @Beta
 class DefaultSdkInfo extends SdkInfo {
     @Override
-    public String getParentViewName(String name) {
+    @Nullable
+    public String getParentViewName(@NonNull String name) {
         return PARENTS.get(name);
     }
 
     @Override
-    public String getParentViewClass(String fqcn) {
+    @Nullable
+    public String getParentViewClass(@NonNull String fqcn) {
         int index = fqcn.lastIndexOf('.');
         if (index != -1) {
             fqcn = fqcn.substring(index + 1);
@@ -94,7 +98,7 @@ class DefaultSdkInfo extends SdkInfo {
     }
 
     @Override
-    public boolean isSubViewOf(String parent, String child) {
+    public boolean isSubViewOf(@NonNull String parent, @NonNull String child) {
         // Do analysis just on non-fqcn paths
         if (parent.indexOf('.') != -1) {
             parent = parent.substring(parent.lastIndexOf('.') + 1);
@@ -117,7 +121,10 @@ class DefaultSdkInfo extends SdkInfo {
     }
 
     private static final int CLASS_COUNT = 56;
+
+    @NonNull
     private static final Map<String, String> PARENTS = new HashMap<String, String>(CLASS_COUNT);
+
     static {
         PARENTS.put(COMPOUND_BUTTON, VIEW);
         PARENTS.put(ABS_SPINNER, ADAPTER_VIEW);
diff --git a/lint/libs/lint_api/src/com/android/tools/lint/client/api/IDomParser.java b/lint/libs/lint_api/src/com/android/tools/lint/client/api/IDomParser.java
index 743e0c5..871133b 100644
--- a/lint/libs/lint_api/src/com/android/tools/lint/client/api/IDomParser.java
+++ b/lint/libs/lint_api/src/com/android/tools/lint/client/api/IDomParser.java
@@ -16,6 +16,8 @@
 
 package com.android.tools.lint.client.api;
 
+import com.android.annotations.NonNull;
+import com.android.annotations.Nullable;
 import com.android.tools.lint.detector.api.Context;
 import com.android.tools.lint.detector.api.Location;
 import com.android.tools.lint.detector.api.XmlContext;
@@ -42,7 +44,8 @@ public interface IDomParser {
      *            editor buffer in the surrounding tool, etc)
      * @return the parsed DOM document, or null if parsing fails
      */
-    Document parseXml(XmlContext context);
+    @Nullable
+    Document parseXml(@NonNull XmlContext context);
 
     /**
      * Returns a {@link Location} for the given DOM node
@@ -51,7 +54,8 @@ public interface IDomParser {
      * @param node the node to create a location for
      * @return a location for the given node
      */
-    Location getLocation(XmlContext context, Node node);
+    @NonNull
+    Location getLocation(@NonNull XmlContext context, @NonNull Node node);
 
     /**
      * Creates a light-weight handle to a location for the given node. It can be
@@ -63,12 +67,13 @@ public interface IDomParser {
      *            for
      * @return a location handle
      */
-    Location.Handle createLocationHandle(XmlContext context, Node node);
+    @NonNull
+    Location.Handle createLocationHandle(@NonNull XmlContext context, @NonNull Node node);
 
     /**
      * Dispose any data structures held for the given context.
      * @param context information about the file previously parsed
      * @param document the document that was parsed and is now being disposed
      */
-    void dispose(XmlContext context, Document document);
+    void dispose(@NonNull XmlContext context, @NonNull Document document);
 }
diff --git a/lint/libs/lint_api/src/com/android/tools/lint/client/api/IJavaParser.java b/lint/libs/lint_api/src/com/android/tools/lint/client/api/IJavaParser.java
index 4de463b..34a9306 100644
--- a/lint/libs/lint_api/src/com/android/tools/lint/client/api/IJavaParser.java
+++ b/lint/libs/lint_api/src/com/android/tools/lint/client/api/IJavaParser.java
@@ -16,6 +16,8 @@
 
 package com.android.tools.lint.client.api;
 
+import com.android.annotations.NonNull;
+import com.android.annotations.Nullable;
 import com.android.tools.lint.detector.api.Context;
 import com.android.tools.lint.detector.api.JavaContext;
 import com.android.tools.lint.detector.api.Location;
@@ -40,7 +42,8 @@ public interface IJavaParser {
      *            editor buffer in the surrounding tool, etc)
      * @return the compilation unit node for the file
      */
-    Node parseJava(JavaContext context);
+    @Nullable
+    Node parseJava(@NonNull JavaContext context);
 
     /**
      * Returns a {@link Location} for the given node
@@ -49,7 +52,8 @@ public interface IJavaParser {
      * @param node the node to create a location for
      * @return a location for the given node
      */
-    Location getLocation(JavaContext context, Node node);
+    @NonNull
+    Location getLocation(@NonNull JavaContext context, @NonNull Node node);
 
     /**
      * Creates a light-weight handle to a location for the given node. It can be
@@ -61,12 +65,13 @@ public interface IJavaParser {
      *            for
      * @return a location handle
      */
-    Location.Handle createLocationHandle(XmlContext context, Node node);
+    @NonNull
+    Location.Handle createLocationHandle(@NonNull XmlContext context, @NonNull Node node);
 
     /**
      * Dispose any data structures held for the given context.
      * @param context information about the file previously parsed
      * @param compilationUnit the compilation unit being disposed
      */
-    void dispose(JavaContext context, Node compilationUnit);
+    void dispose(@NonNull JavaContext context, @NonNull Node compilationUnit);
 }
diff --git a/lint/libs/lint_api/src/com/android/tools/lint/client/api/IssueRegistry.java b/lint/libs/lint_api/src/com/android/tools/lint/client/api/IssueRegistry.java
index 67efe36..a809841 100644
--- a/lint/libs/lint_api/src/com/android/tools/lint/client/api/IssueRegistry.java
+++ b/lint/libs/lint_api/src/com/android/tools/lint/client/api/IssueRegistry.java
@@ -16,6 +16,8 @@
 
 package com.android.tools.lint.client.api;
 
+import com.android.annotations.NonNull;
+import com.android.annotations.Nullable;
 import com.android.tools.lint.detector.api.Category;
 import com.android.tools.lint.detector.api.Detector;
 import com.android.tools.lint.detector.api.Issue;
@@ -46,6 +48,7 @@ public abstract class IssueRegistry {
      * Issue reported by lint (not a specific detector) when it cannot even
      * parse an XML file prior to analysis
      */
+    @NonNull
     public static final Issue PARSER_ERROR = Issue.create(
             "ParserError", //$NON-NLS-1$
             "Finds files that contain fatal parser errors",
@@ -63,6 +66,7 @@ public abstract class IssueRegistry {
      * @return the list of issues to be checked (including those that may be
      *         disabled!)
      */
+    @NonNull
     public abstract List<Issue> getIssues();
 
     /**
@@ -79,11 +83,12 @@ public abstract class IssueRegistry {
      *            the applicable detectors for that scope
      * @return a list of new detector instances
      */
+    @NonNull
     final List<? extends Detector> createDetectors(
-            LintClient client,
-            Configuration configuration,
-            EnumSet<Scope> scope,
-            Map<Scope, List<Detector>> scopeToDetectors) {
+            @NonNull LintClient client,
+            @NonNull Configuration configuration,
+            @NonNull EnumSet<Scope> scope,
+            @Nullable Map<Scope, List<Detector>> scopeToDetectors) {
         List<Issue> issues = getIssues();
         Set<Class<? extends Detector>> detectorClasses = new HashSet<Class<? extends Detector>>();
         Map<Class<? extends Detector>, EnumSet<Scope>> detectorToScope =
@@ -152,7 +157,7 @@ public abstract class IssueRegistry {
      * @param id the id to be checked
      * @return true if the given id is valid
      */
-    public final boolean isIssueId(String id) {
+    public final boolean isIssueId(@NonNull String id) {
         return getIssue(id) != null;
     }
 
@@ -162,7 +167,7 @@ public abstract class IssueRegistry {
      * @param name the category name to be checked
      * @return true if the given string is a valid category
      */
-    public final boolean isCategoryName(String name) {
+    public final boolean isCategoryName(@NonNull String name) {
         for (Category c : getCategories()) {
             if (c.getName().equals(name) || c.getFullName().equals(name)) {
                 return true;
@@ -177,6 +182,7 @@ public abstract class IssueRegistry {
      *
      * @return an iterator for all the categories, never null
      */
+    @NonNull
     public List<Category> getCategories() {
         if (sCategories == null) {
             final Set<Category> categories = new HashSet<Category>();
@@ -197,7 +203,8 @@ public abstract class IssueRegistry {
      * @param id the id to be checked
      * @return the corresponding issue, or null
      */
-    public final Issue getIssue(String id) {
+    @Nullable
+    public final Issue getIssue(@NonNull String id) {
         if (sIdToIssue == null) {
             List<Issue> issues = getIssues();
             sIdToIssue = new HashMap<String, Issue>(issues.size());
diff --git a/lint/libs/lint_api/src/com/android/tools/lint/client/api/JavaVisitor.java b/lint/libs/lint_api/src/com/android/tools/lint/client/api/JavaVisitor.java
index 14a0627..63b51b5 100644
--- a/lint/libs/lint_api/src/com/android/tools/lint/client/api/JavaVisitor.java
+++ b/lint/libs/lint_api/src/com/android/tools/lint/client/api/JavaVisitor.java
@@ -16,6 +16,7 @@
 
 package com.android.tools.lint.client.api;
 
+import com.android.annotations.NonNull;
 import com.android.tools.lint.detector.api.Detector;
 import com.android.tools.lint.detector.api.Detector.JavaScanner;
 import com.android.tools.lint.detector.api.Detector.XmlScanner;
@@ -136,7 +137,7 @@ public class JavaVisitor {
             new HashMap<Class<? extends Node>, List<VisitingDetector>>();
     private final IJavaParser mParser;
 
-    JavaVisitor(IJavaParser parser, List<Detector> detectors) {
+    JavaVisitor(@NonNull IJavaParser parser, @NonNull List<Detector> detectors) {
         mParser = parser;
         mAllDetectors = new ArrayList<VisitingDetector>(detectors.size());
         mFullTreeDetectors = new ArrayList<VisitingDetector>(detectors.size());
@@ -182,7 +183,7 @@ public class JavaVisitor {
         }
     }
 
-    void visitFile(JavaContext context, File file) {
+    void visitFile(@NonNull JavaContext context, @NonNull File file) {
         context.parser = mParser;
 
         Node compilationUnit = null;
@@ -233,20 +234,22 @@ public class JavaVisitor {
         public final Detector mDetector;
         public final JavaScanner mJavaScanner;
 
-        public VisitingDetector(Detector detector, JavaScanner javaScanner) {
+        public VisitingDetector(@NonNull Detector detector, @NonNull JavaScanner javaScanner) {
             mDetector = detector;
             mJavaScanner = javaScanner;
         }
 
+        @NonNull
         public Detector getDetector() {
             return mDetector;
         }
 
+        @NonNull
         public JavaScanner getJavaScanner() {
             return mJavaScanner;
         }
 
-        public void setContext(JavaContext context) {
+        public void setContext(@NonNull JavaContext context) {
             mContext = context;
 
             // The visitors are one-per-context, so clear them out here and construct
@@ -254,6 +257,7 @@ public class JavaVisitor {
             mVisitor = null;
         }
 
+        @NonNull
         AstVisitor getVisitor() {
             if (mVisitor == null) {
                 mVisitor = mDetector.createJavaVisitor(mContext);
@@ -1106,7 +1110,7 @@ public class JavaVisitor {
         }
 
         @Override
-        public boolean visitVariableReference(VariableReference node) {
+        public boolean visitVariableReference(@NonNull VariableReference node) {
             if (mVisitResources) {
                 if (node.astIdentifier().getDescription().equals("R") && //$NON-NLS-1$
                         node.getParent() instanceof Select &&
@@ -1128,7 +1132,7 @@ public class JavaVisitor {
         }
 
         @Override
-        public boolean visitMethodInvocation(MethodInvocation node) {
+        public boolean visitMethodInvocation(@NonNull MethodInvocation node) {
             if (mVisitMethods) {
                 String methodName = node.astName().getDescription();
                 List<VisitingDetector> list = mMethodDetectors.get(methodName);
diff --git a/lint/libs/lint_api/src/com/android/tools/lint/client/api/Lint.java b/lint/libs/lint_api/src/com/android/tools/lint/client/api/Lint.java
index ac28b47..e3df54f 100644
--- a/lint/libs/lint_api/src/com/android/tools/lint/client/api/Lint.java
+++ b/lint/libs/lint_api/src/com/android/tools/lint/client/api/Lint.java
@@ -19,6 +19,8 @@ package com.android.tools.lint.client.api;
 import static com.android.tools.lint.detector.api.LintConstants.DOT_CLASS;
 import static com.android.tools.lint.detector.api.LintConstants.DOT_JAVA;
 
+import com.android.annotations.NonNull;
+import com.android.annotations.Nullable;
 import com.android.resources.ResourceFolderType;
 import com.android.tools.lint.client.api.LintListener.EventType;
 import com.android.tools.lint.detector.api.Category;
@@ -80,8 +82,7 @@ public class Lint {
      * @param registry The registry containing issues to be checked
      * @param client the tool wrapping the analyzer, such as an IDE or a CLI
      */
-    public Lint(IssueRegistry registry, LintClient client) {
-        assert client != null;
+    public Lint(@NonNull IssueRegistry registry, @NonNull LintClient client) {
         mRegistry = registry;
         mClient = new LintClientWrapper(client);
     }
@@ -99,7 +100,7 @@ public class Lint {
      * @param scope the scope of the analysis; detectors with a wider scope will
      *            not be run. If null, the scope will be inferred from the files.
      */
-    public void analyze(List<File> files, EnumSet<Scope> scope) {
+    public void analyze(@NonNull List<File> files, @Nullable EnumSet<Scope> scope) {
         mCanceled = false;
         mScope = scope;
 
@@ -158,7 +159,7 @@ public class Lint {
         fireEvent(mCanceled ? EventType.CANCELED : EventType.COMPLETED, null);
     }
 
-    private void computeDetectors(Project project) {
+    private void computeDetectors(@NonNull Project project) {
         // Ensure that the current visitor is recomputed
         mCurrentFolderType = null;
         mCurrentVisitor = null;
@@ -212,12 +213,15 @@ public class Lint {
         }
     }
 
-    private void registerProjectFile(Map<File, Project> fileToProject, File file,
-            File projectDir, File rootDir) {
+    private void registerProjectFile(
+            @NonNull Map<File, Project> fileToProject,
+            @NonNull File file,
+            @NonNull File projectDir,
+            @NonNull File rootDir) {
         fileToProject.put(file, mClient.getProject(projectDir, rootDir));
     }
 
-    private Collection<Project> computeProjects(List<File> files) {
+    private Collection<Project> computeProjects(@NonNull List<File> files) {
         // Compute list of projects
         Map<File, Project> fileToProject = new HashMap<File, Project>();
 
@@ -310,7 +314,10 @@ public class Lint {
         return roots;
     }
 
-    private void addProjects(File dir, Map<File, Project> fileToProject, File rootDir) {
+    private void addProjects(
+            @NonNull File dir,
+            @NonNull Map<File, Project> fileToProject,
+            @NonNull File rootDir) {
         if (mCanceled) {
             return;
         }
@@ -329,12 +336,11 @@ public class Lint {
         }
     }
 
-    private boolean isProjectDir(File dir) {
+    private boolean isProjectDir(@NonNull File dir) {
         return new File(dir, ANDROID_MANIFEST_XML).exists();
     }
 
-    private void checkProject(Project project) {
-
+    private void checkProject(@NonNull Project project) {
         File projectDir = project.getDir();
 
         Context projectContext = new Context(mClient, project, null, projectDir, mScope);
@@ -396,8 +402,7 @@ public class Lint {
         }
     }
 
-    private void runFileDetectors(Project project, Project main) {
-
+    private void runFileDetectors(@NonNull Project project, @Nullable Project main) {
         // Look up manifest information (but not for library projects)
         File manifestFile = new File(project.getDir(), ANDROID_MANIFEST_XML);
         if (!project.isLibrary() && manifestFile.exists()) {
@@ -423,7 +428,7 @@ public class Lint {
         if (mScope.contains(Scope.ALL_RESOURCE_FILES) || mScope.contains(Scope.RESOURCE_FILE)) {
             List<Detector> checks = union(mScopeDetectors.get(Scope.RESOURCE_FILE),
                     mScopeDetectors.get(Scope.ALL_RESOURCE_FILES));
-            if (checks.size() > 0) {
+            if (checks != null && checks.size() > 0) {
                 List<ResourceXmlDetector> xmlDetectors =
                         new ArrayList<ResourceXmlDetector>(checks.size());
                 for (Detector detector : checks) {
@@ -452,7 +457,7 @@ public class Lint {
         if (mScope.contains(Scope.JAVA_FILE) || mScope.contains(Scope.ALL_JAVA_FILES)) {
             List<Detector> checks = union(mScopeDetectors.get(Scope.JAVA_FILE),
                     mScopeDetectors.get(Scope.ALL_JAVA_FILES));
-            if (checks.size() > 0) {
+            if (checks != null && checks.size() > 0) {
                 List<File> sourceFolders = project.getJavaSourceFolders();
                 checkJava(project, main, sourceFolders, checks);
             }
@@ -493,24 +498,35 @@ public class Lint {
         }
     }
 
-    private static List<Detector> union(List<Detector> list1, List<Detector> list2) {
-        int size = (list1 != null ? list1.size() : 0) + (list2 != null ? list2.size() : 0);
-        // Use set to pick out unique detectors, since it's possible for there to be overlap,
-        // e.g. the DuplicateIdDetector registers both a cross-resource issue and a
-        // single-file issue, so it shows up on both scope lists:
-        Set<Detector> set = new HashSet<Detector>(size);
-        if (list1 != null) {
-            set.addAll(list1);
-        }
-        if (list2 != null) {
-            set.addAll(list2);
-        }
+    @Nullable
+    private static List<Detector> union(
+            @Nullable List<Detector> list1,
+            @Nullable List<Detector> list2) {
+        if (list1 == null) {
+            return list2;
+        } else if (list2 == null) {
+            return list1;
+        } else {
+            // Use set to pick out unique detectors, since it's possible for there to be overlap,
+            // e.g. the DuplicateIdDetector registers both a cross-resource issue and a
+            // single-file issue, so it shows up on both scope lists:
+            Set<Detector> set = new HashSet<Detector>(list1.size() + list2.size());
+            if (list1 != null) {
+                set.addAll(list1);
+            }
+            if (list2 != null) {
+                set.addAll(list2);
+            }
 
-        return new ArrayList<Detector>(set);
+            return new ArrayList<Detector>(set);
+        }
     }
 
-    private void checkClasses(Project project, Project main,
-            List<File> binFolders, List<Detector> checks) {
+    private void checkClasses(
+            @NonNull Project project,
+            @Nullable Project main,
+            @NonNull List<File> binFolders,
+            @NonNull List<Detector> checks) {
         if (binFolders.size() == 0) {
             //mClient.log(null, "Warning: Class-file checks are enabled, but no " +
             //        "output folders found. Does the project need to be built first?");
@@ -557,7 +573,7 @@ public class Lint {
         }
     }
 
-    private void addClassFiles(File dir, List<File> classFiles) {
+    private void addClassFiles(@NonNull File dir, @NonNull List<File> classFiles) {
         // Process the resource folder
         File[] files = dir.listFiles();
         if (files != null && files.length > 0) {
@@ -572,8 +588,11 @@ public class Lint {
         }
     }
 
-    private void checkJava(Project project, Project main,
-            List<File> sourceFolders, List<Detector> checks) {
+    private void checkJava(
+            @NonNull Project project,
+            @Nullable Project main,
+            @NonNull List<File> sourceFolders,
+            @NonNull List<Detector> checks) {
         IJavaParser javaParser = mClient.getJavaParser();
         if (javaParser == null) {
             mClient.log(null, "No java parser provided to lint: not running Java checks");
@@ -600,7 +619,7 @@ public class Lint {
         }
     }
 
-    private void gatherJavaFiles(File dir, List<File> result) {
+    private void gatherJavaFiles(@NonNull File dir, @NonNull List<File> result) {
         File[] files = dir.listFiles();
         if (files != null) {
             for (File file : files) {
@@ -617,7 +636,10 @@ public class Lint {
     private List<ResourceXmlDetector> mCurrentXmlDetectors;
     private XmlVisitor mCurrentVisitor;
 
-    private XmlVisitor getVisitor(ResourceFolderType type, List<ResourceXmlDetector> checks) {
+    @Nullable
+    private XmlVisitor getVisitor(
+            @NonNull ResourceFolderType type,
+            @NonNull List<ResourceXmlDetector> checks) {
         if (type != mCurrentFolderType) {
             mCurrentFolderType = type;
 
@@ -646,8 +668,11 @@ public class Lint {
         return mCurrentVisitor;
     }
 
-    private void checkResFolder(Project project, Project main, File res,
-            List<ResourceXmlDetector> checks) {
+    private void checkResFolder(
+            @NonNull Project project,
+            @Nullable Project main,
+            @NonNull File res,
+            @NonNull List<ResourceXmlDetector> checks) {
         assert res.isDirectory();
         File[] resourceDirs = res.listFiles();
         if (resourceDirs == null) {
@@ -671,8 +696,12 @@ public class Lint {
         }
     }
 
-    private void checkResourceFolder(Project project, Project main, File dir,
-            ResourceFolderType type, List<ResourceXmlDetector> checks) {
+    private void checkResourceFolder(
+            @NonNull Project project,
+            @Nullable Project main,
+            @NonNull File dir,
+            @NonNull ResourceFolderType type,
+            @NonNull List<ResourceXmlDetector> checks) {
         // Process the resource folder
         File[] xmlFiles = dir.listFiles();
         if (xmlFiles != null && xmlFiles.length > 0) {
@@ -694,8 +723,11 @@ public class Lint {
     }
 
     /** Checks individual resources */
-    private void checkIndividualResources(Project project, Project main,
-            List<ResourceXmlDetector> xmlDetectors, List<File> files) {
+    private void checkIndividualResources(
+            @NonNull Project project,
+            @Nullable Project main,
+            @NonNull List<ResourceXmlDetector> xmlDetectors,
+            @NonNull List<File> files) {
         for (File file : files) {
             if (file.isDirectory()) {
                 // Is it a resource folder?
@@ -733,7 +765,7 @@ public class Lint {
      *
      * @param listener the listener to be added
      */
-    public void addLintListener(LintListener listener) {
+    public void addLintListener(@NonNull LintListener listener) {
         if (mListeners == null) {
             mListeners = new ArrayList<LintListener>(1);
         }
@@ -745,7 +777,7 @@ public class Lint {
      *
      * @param listener the listener to be removed
      */
-    public void removeLintListener(LintListener listener) {
+    public void removeLintListener(@NonNull LintListener listener) {
         mListeners.remove(listener);
         if (mListeners.size() == 0) {
             mListeners = null;
@@ -753,7 +785,7 @@ public class Lint {
     }
 
     /** Notifies listeners, if any, that the given event has occurred */
-    private void fireEvent(LintListener.EventType type, Context context) {
+    private void fireEvent(@NonNull LintListener.EventType type, @NonNull Context context) {
         if (mListeners != null) {
             for (int i = 0, n = mListeners.size(); i < n; i++) {
                 LintListener listener = mListeners.get(i);
@@ -771,15 +803,20 @@ public class Lint {
      * filtered out warnings.
      */
     private static class LintClientWrapper extends LintClient {
-        private LintClient mDelegate;
+        @NonNull
+        private final LintClient mDelegate;
 
-        public LintClientWrapper(LintClient delegate) {
+        public LintClientWrapper(@NonNull LintClient delegate) {
             mDelegate = delegate;
         }
 
         @Override
-        public void report(Context context, Issue issue, Location location, String message,
-                Object data) {
+        public void report(
+                @NonNull Context context,
+                @NonNull Issue issue,
+                @Nullable Location location,
+                @NonNull String message,
+                @Nullable Object data) {
             Configuration configuration = context.getConfiguration();
             if (!configuration.isEnabled(issue)) {
                 if (issue != IssueRegistry.PARSER_ERROR) {
@@ -804,52 +841,62 @@ public class Lint {
         // Everything else just delegates to the embedding lint client
 
         @Override
-        public Configuration getConfiguration(Project project) {
+        @NonNull
+        public Configuration getConfiguration(@NonNull Project project) {
             return mDelegate.getConfiguration(project);
         }
 
 
         @Override
-        public void log(Throwable exception, String format, Object... args) {
+        public void log(@Nullable Throwable exception, @Nullable String format,
+                @Nullable Object... args) {
             mDelegate.log(exception, format, args);
         }
 
         @Override
-        public String readFile(File file) {
+        @NonNull
+        public String readFile(@NonNull File file) {
             return mDelegate.readFile(file);
         }
 
         @Override
-        public List<File> getJavaSourceFolders(Project project) {
+        @NonNull
+        public List<File> getJavaSourceFolders(@NonNull Project project) {
             return mDelegate.getJavaSourceFolders(project);
         }
 
         @Override
-        public List<File> getJavaClassFolders(Project project) {
+        @NonNull
+        public List<File> getJavaClassFolders(@NonNull Project project) {
             return mDelegate.getJavaClassFolders(project);
         }
 
         @Override
+        @Nullable
         public IDomParser getDomParser() {
             return mDelegate.getDomParser();
         }
 
         @Override
+        @NonNull
         public Class<? extends Detector> replaceDetector(Class<? extends Detector> detectorClass) {
             return mDelegate.replaceDetector(detectorClass);
         }
 
         @Override
+        @NonNull
         public SdkInfo getSdkInfo(Project project) {
             return mDelegate.getSdkInfo(project);
         }
 
         @Override
-        public Project getProject(File dir, File referenceDir) {
+        @NonNull
+        public Project getProject(@NonNull File dir, @NonNull File referenceDir) {
             return mDelegate.getProject(dir, referenceDir);
         }
 
         @Override
+        @Nullable
         public IJavaParser getJavaParser() {
             return mDelegate.getJavaParser();
         }
diff --git a/lint/libs/lint_api/src/com/android/tools/lint/client/api/LintClient.java b/lint/libs/lint_api/src/com/android/tools/lint/client/api/LintClient.java
index 10d21ed..91f6fe5 100644
--- a/lint/libs/lint_api/src/com/android/tools/lint/client/api/LintClient.java
+++ b/lint/libs/lint_api/src/com/android/tools/lint/client/api/LintClient.java
@@ -16,6 +16,8 @@
 
 package com.android.tools.lint.client.api;
 
+import com.android.annotations.NonNull;
+import com.android.annotations.Nullable;
 import com.android.tools.lint.detector.api.Context;
 import com.android.tools.lint.detector.api.Detector;
 import com.android.tools.lint.detector.api.Issue;
@@ -58,7 +60,7 @@ public abstract class LintClient {
      * @param project the project to obtain a configuration for
      * @return a configuration, never null.
      */
-    public Configuration getConfiguration(Project project) {
+    public Configuration getConfiguration(@NonNull Project project) {
         return DefaultConfiguration.create(this, project, null);
     }
 
@@ -80,30 +82,42 @@ public abstract class LintClient {
      *            error message text. See each detector for details on which
      *            data if any is supplied for a given issue.
      */
-    public abstract void report(Context context, Issue issue, Location location, String message,
-            Object data);
+    public abstract void report(
+            @NonNull Context context,
+            @NonNull Issue issue,
+            @Nullable Location location,
+            @NonNull String message,
+            @Nullable Object data);
 
     /**
      * Send an exception to the log
      *
      * @param exception the exception, possibly null
-     * @param format the error message using {@link String#format} syntax
+     * @param format the error message using {@link String#format} syntax, possibly null
+     *    (though in that case the exception should not be null)
      * @param args any arguments for the format string
      */
-    public abstract void log(Throwable exception, String format, Object... args);
+    public abstract void log(
+            @Nullable Throwable exception,
+            @Nullable String format,
+            @Nullable Object... args);
 
     /**
      * Returns a {@link IDomParser} to use to parse XML
      *
-     * @return a new {@link IDomParser}
+     * @return a new {@link IDomParser}, or null if this client does not support
+     *         XML analysis
      */
+    @Nullable
     public abstract IDomParser getDomParser();
 
     /**
      * Returns a {@link IJavaParser} to use to parse Java
      *
-     * @return a new {@link IJavaParser}
+     * @return a new {@link IJavaParser}, or null if this client does not
+     *         support Java analysis
      */
+    @Nullable
     public abstract IJavaParser getJavaParser();
 
     /**
@@ -114,7 +128,9 @@ public abstract class LintClient {
      * @param detectorClass the class of the detector to be replaced
      * @return the new detector class, or just the original detector (not null)
      */
-    public Class<? extends Detector> replaceDetector(Class<? extends Detector> detectorClass) {
+    @NonNull
+    public Class<? extends Detector> replaceDetector(
+            @NonNull Class<? extends Detector> detectorClass) {
         return detectorClass;
     }
 
@@ -125,7 +141,8 @@ public abstract class LintClient {
      * @return the string to return, never null (will be empty if there is an
      *         I/O error)
      */
-    public abstract String readFile(File file);
+    @NonNull
+    public abstract String readFile(@NonNull File file);
 
     /**
      * Returns the list of source folders for Java source files
@@ -133,7 +150,8 @@ public abstract class LintClient {
      * @param project the project to look up Java source file locations for
      * @return a list of source folders to search for .java files
      */
-    public List<File> getJavaSourceFolders(Project project) {
+    @NonNull
+    public List<File> getJavaSourceFolders(@NonNull Project project) {
         return getEclipseClasspath(project, "src", "src", "gen"); //$NON-NLS-1$ //$NON-NLS-2$
     }
 
@@ -142,7 +160,8 @@ public abstract class LintClient {
      * @param project the project to look up class file locations for
      * @return a list of output folders to search for .class files
      */
-    public List<File> getJavaClassFolders(Project project) {
+    @NonNull
+    public List<File> getJavaClassFolders(@NonNull Project project) {
         return getEclipseClasspath(project, "output", "bin"); //$NON-NLS-1$ //$NON-NLS-2$
     }
 
@@ -152,7 +171,8 @@ public abstract class LintClient {
      * @param project the project to look up an {@link SdkInfo} for
      * @return an {@link SdkInfo} for the project
      */
-    public SdkInfo getSdkInfo(Project project) {
+    @NonNull
+    public SdkInfo getSdkInfo(@NonNull Project project) {
         // By default no per-platform SDK info
         return new DefaultSdkInfo();
     }
@@ -161,8 +181,9 @@ public abstract class LintClient {
      * Considers the given directory as an Eclipse project and returns either
      * its source or its output folders depending on the {@code attribute} parameter.
      */
-    private List<File> getEclipseClasspath(Project project, String attribute,
-            String... fallbackPaths) {
+    @NonNull
+    private List<File> getEclipseClasspath(@NonNull Project project, @NonNull String attribute,
+            @NonNull String... fallbackPaths) {
         List<File> folders = new ArrayList<File>();
         File projectDir = project.getDir();
         File classpathFile = new File(projectDir, ".classpath"); //$NON-NLS-1$
@@ -220,7 +241,8 @@ public abstract class LintClient {
      * @param referenceDir See {@link Project#getReferenceDir()}.
      * @return a project, never null
      */
-    public Project getProject(File dir, File referenceDir) {
+    @NonNull
+    public Project getProject(@NonNull File dir, @NonNull File referenceDir) {
         if (mDirToProject == null) {
             mDirToProject = new HashMap<File, Project>();
         }
diff --git a/lint/libs/lint_api/src/com/android/tools/lint/client/api/LintListener.java b/lint/libs/lint_api/src/com/android/tools/lint/client/api/LintListener.java
index d6ead4d..49c54a7 100644
--- a/lint/libs/lint_api/src/com/android/tools/lint/client/api/LintListener.java
+++ b/lint/libs/lint_api/src/com/android/tools/lint/client/api/LintListener.java
@@ -16,6 +16,7 @@
 
 package com.android.tools.lint.client.api;
 
+import com.android.annotations.NonNull;
 import com.android.tools.lint.detector.api.Context;
 import com.google.common.annotations.Beta;
 
@@ -59,5 +60,5 @@ public interface LintListener {
      * @param type the type of event that occurred
      * @param context the context providing additional information
      */
-    public void update(EventType type, Context context);
+    public void update(@NonNull EventType type, @NonNull Context context);
 }
diff --git a/lint/libs/lint_api/src/com/android/tools/lint/client/api/SdkInfo.java b/lint/libs/lint_api/src/com/android/tools/lint/client/api/SdkInfo.java
index 9da87a8..b16747c 100644
--- a/lint/libs/lint_api/src/com/android/tools/lint/client/api/SdkInfo.java
+++ b/lint/libs/lint_api/src/com/android/tools/lint/client/api/SdkInfo.java
@@ -16,6 +16,8 @@
 
 package com.android.tools.lint.client.api;
 
+import com.android.annotations.NonNull;
+import com.android.annotations.Nullable;
 import com.google.common.annotations.Beta;
 
 /**
@@ -35,7 +37,7 @@ public abstract class SdkInfo {
      * @return true if the child view is a sub view of (or the same class as)
      *         the parent view
      */
-    public boolean isSubViewOf(String parentViewFqcn, String childViewFqcn) {
+    public boolean isSubViewOf(@NonNull String parentViewFqcn, @NonNull String childViewFqcn) {
         while (!childViewFqcn.equals("android.view.View")) { //$NON-NLS-1$
             if (parentViewFqcn.equals(childViewFqcn)) {
                 return true;
@@ -58,7 +60,8 @@ public abstract class SdkInfo {
      * @param fqcn the fully qualified class name of the view
      * @return the fully qualified class name of the parent view, or null
      */
-    public abstract String getParentViewClass(String fqcn);
+    @Nullable
+    public abstract String getParentViewClass(@NonNull String fqcn);
 
     /**
      * Returns the class name of the parent view, or null if the view is the
@@ -69,7 +72,8 @@ public abstract class SdkInfo {
      *            package)
      * @return the view name of the parent
      */
-    public abstract String getParentViewName(String name);
+    @Nullable
+    public abstract String getParentViewName(@NonNull String name);
 
     // TODO: Add access to resource resolution here.
 }
diff --git a/lint/libs/lint_api/src/com/android/tools/lint/client/api/XmlVisitor.java b/lint/libs/lint_api/src/com/android/tools/lint/client/api/XmlVisitor.java
index 15fd123..ec6bd6a 100644
--- a/lint/libs/lint_api/src/com/android/tools/lint/client/api/XmlVisitor.java
+++ b/lint/libs/lint_api/src/com/android/tools/lint/client/api/XmlVisitor.java
@@ -16,6 +16,7 @@
 
 package com.android.tools.lint.client.api;
 
+import com.android.annotations.NonNull;
 import com.android.tools.lint.detector.api.Detector;
 import com.android.tools.lint.detector.api.Detector.XmlScanner;
 import com.android.tools.lint.detector.api.LintUtils;
@@ -73,7 +74,7 @@ class XmlVisitor {
     //<T extends List<Detector> & Detector.XmlScanner> XmlVisitor(IDomParser parser,
     //    T xmlDetectors) {
     // but it makes client code tricky and ugly.
-    XmlVisitor(IDomParser parser, List<? extends Detector> xmlDetectors) {
+    XmlVisitor(@NonNull IDomParser parser, @NonNull List<? extends Detector> xmlDetectors) {
         mParser = parser;
         mAllDetectors = xmlDetectors;
 
@@ -117,7 +118,7 @@ class XmlVisitor {
         }
     }
 
-    void visitFile(XmlContext context, File file) {
+    void visitFile(@NonNull XmlContext context,@NonNull  File file) {
         assert LintUtils.isXmlFile(file);
         context.parser = mParser;
 
@@ -160,7 +161,7 @@ class XmlVisitor {
         }
     }
 
-    private void visitElement(XmlContext context, Element element) {
+    private void visitElement(@NonNull XmlContext context, @NonNull Element element) {
         List<Detector.XmlScanner> elementChecks = mElementToCheck.get(element.getTagName());
         if (elementChecks != null) {
             assert elementChecks instanceof RandomAccess;
diff --git a/lint/libs/lint_api/src/com/android/tools/lint/detector/api/Category.java b/lint/libs/lint_api/src/com/android/tools/lint/detector/api/Category.java
index 88ceb17..a318fc7 100644
--- a/lint/libs/lint_api/src/com/android/tools/lint/detector/api/Category.java
+++ b/lint/libs/lint_api/src/com/android/tools/lint/detector/api/Category.java
@@ -16,6 +16,8 @@
 
 package com.android.tools.lint.detector.api;
 
+import com.android.annotations.NonNull;
+import com.android.annotations.Nullable;
 import com.google.common.annotations.Beta;
 
 /**
@@ -39,7 +41,11 @@ public final class Category implements Comparable<Category> {
      * @param explanation an optional explanation of the category
      * @param priority a sorting priority, with higher being more important
      */
-    private Category(Category parent, String name, String explanation, int priority) {
+    private Category(
+            @Nullable Category parent,
+            @NonNull String name,
+            @Nullable String explanation,
+            int priority) {
         mParent = parent;
         mName = name;
         mExplanation = explanation;
@@ -53,7 +59,8 @@ public final class Category implements Comparable<Category> {
      * @param priority a sorting priority, with higher being more important
      * @return a new category
      */
-    public static Category create(String name, int priority) {
+    @NonNull
+    public static Category create(@NonNull String name, int priority) {
         return new Category(null, name, null, priority);
     }
 
@@ -66,7 +73,12 @@ public final class Category implements Comparable<Category> {
      * @param priority a sorting priority, with higher being more important
      * @return a new category
      */
-    public static Category create(Category parent, String name, String explanation, int priority) {
+    @NonNull
+    public static Category create(
+            @Nullable Category parent,
+            @NonNull String name,
+            @Nullable String explanation,
+            int priority) {
         return new Category(parent, name, null, priority);
     }
 
@@ -113,7 +125,7 @@ public final class Category implements Comparable<Category> {
     }
 
     @Override
-    public int compareTo(Category other) {
+    public int compareTo(@NonNull Category other) {
         if (other.mPriority == mPriority) {
             if (mParent == other) {
                 return 1;
@@ -126,22 +138,30 @@ public final class Category implements Comparable<Category> {
 
     /** Issues related to correctness */
     public static final Category CORRECTNESS = Category.create("Correctness", 10);
+
     /** Issues related to security */
     public static final Category SECURITY = Category.create("Security", 9);
+
     /** Issues related to performance */
     public static final Category PERFORMANCE = Category.create("Performance", 8);
+
     /** Issues related to usability */
     public static final Category USABILITY = Category.create("Usability", 7);
+
     /** Issues related to accessibility */
     public static final Category A11Y = Category.create("Accessibility", 6);
+
     /** Issues related to internationalization */
     public static final Category I18N = Category.create("Internationalization", 5);
 
     // Sub categories
+
     /** Issues related to icons */
     public static final Category ICONS = Category.create(USABILITY, "Icons", null, 7);
+
     /** Issues related to typography */
     public static final Category TYPOGRAPHY = Category.create(USABILITY, "Typography", null, 8);
+
     /** Issues related to messages/strings */
     public static final Category MESSAGES = Category.create(CORRECTNESS, "Messages", null, 10);
 }
diff --git a/lint/libs/lint_api/src/com/android/tools/lint/detector/api/ClassContext.java b/lint/libs/lint_api/src/com/android/tools/lint/detector/api/ClassContext.java
index 86534f3..09ef05c 100644
--- a/lint/libs/lint_api/src/com/android/tools/lint/detector/api/ClassContext.java
+++ b/lint/libs/lint_api/src/com/android/tools/lint/detector/api/ClassContext.java
@@ -19,6 +19,8 @@ package com.android.tools.lint.detector.api;
 import static com.android.tools.lint.detector.api.LintConstants.DOT_CLASS;
 import static com.android.tools.lint.detector.api.LintConstants.DOT_JAVA;
 
+import com.android.annotations.NonNull;
+import com.android.annotations.Nullable;
 import com.android.tools.lint.client.api.LintClient;
 import com.google.common.annotations.Beta;
 
@@ -63,8 +65,15 @@ public class ClassContext extends Context {
      * @param bytes the bytecode raw data
      * @param classNode the bytecode object model
      */
-    public ClassContext(LintClient client, Project project, Project main, File file,
-            EnumSet<Scope> scope, File binDir, byte[] bytes, ClassNode classNode) {
+    public ClassContext(
+            @NonNull LintClient client,
+            @NonNull Project project,
+            @Nullable Project main,
+            @NonNull File file,
+            @NonNull EnumSet<Scope> scope,
+            @NonNull File binDir,
+            @NonNull byte[] bytes,
+            @NonNull ClassNode classNode) {
         super(client, project, main, file, scope);
         mBinDir = binDir;
         mBytes = bytes;
@@ -74,8 +83,9 @@ public class ClassContext extends Context {
     /**
      * Returns the raw bytecode data for this class file
      *
-     * @return the byte array containing the bytecode data, or null
+     * @return the byte array containing the bytecode data
      */
+    @NonNull
     public byte[] getBytecode() {
         return mBytes;
     }
@@ -85,6 +95,7 @@ public class ClassContext extends Context {
      *
      * @return the bytecode object model, never null
      */
+    @NonNull
     public ClassNode getClassNode() {
         return mClassNode;
     }
@@ -94,6 +105,7 @@ public class ClassContext extends Context {
      *
      * @return the source file, or null
      */
+    @Nullable
     public File getSourceFile() {
         if (mSourceFile == null && !mSearchedForSource) {
             mSearchedForSource = true;
@@ -135,6 +147,7 @@ public class ClassContext extends Context {
      *
      * @return the source contents, or ""
      */
+    @NonNull
     public String getSourceContents() {
         if (mSourceContents == null) {
             File sourceFile = getSourceFile();
@@ -150,8 +163,6 @@ public class ClassContext extends Context {
         return mSourceContents;
     }
 
-
-
     /**
      * Returns a location for the given source line number in this class file's
      * source file, if available.
@@ -163,6 +174,7 @@ public class ClassContext extends Context {
      *            end
      * @return a location, never null
      */
+    @NonNull
     public Location getLocationForLine(int line, String patternStart, String patternEnd) {
         File sourceFile = getSourceFile();
         if (sourceFile != null) {
diff --git a/lint/libs/lint_api/src/com/android/tools/lint/detector/api/Context.java b/lint/libs/lint_api/src/com/android/tools/lint/detector/api/Context.java
index db6cca9..0c088d8 100644
--- a/lint/libs/lint_api/src/com/android/tools/lint/detector/api/Context.java
+++ b/lint/libs/lint_api/src/com/android/tools/lint/detector/api/Context.java
@@ -16,6 +16,8 @@
 
 package com.android.tools.lint.detector.api;
 
+import com.android.annotations.NonNull;
+import com.android.annotations.Nullable;
 import com.android.tools.lint.client.api.Configuration;
 import com.android.tools.lint.client.api.LintClient;
 import com.android.tools.lint.client.api.SdkInfo;
@@ -48,6 +50,7 @@ public class Context {
     private final LintClient mClient;
 
     /** The project containing the file being checked */
+    @NonNull
     private final Project mProject;
 
     /**
@@ -80,6 +83,7 @@ public class Context {
      * Slow-running detectors should check this flag via
      * {@link AtomicBoolean#get()} and abort if canceled
      */
+    @NonNull
     public final AtomicBoolean canceled = new AtomicBoolean();
 
     /** Map of properties to share results between detectors */
@@ -97,8 +101,12 @@ public class Context {
      * @param file the file being checked
      * @param scope the scope for the lint job
      */
-    public Context(LintClient client, Project project, Project main, File file,
-            EnumSet<Scope> scope) {
+    public Context(
+            @NonNull LintClient client,
+            @NonNull Project project,
+            @Nullable Project main,
+            @NonNull File file,
+            @NonNull EnumSet<Scope> scope) {
         this.file = file;
 
         mClient = client;
@@ -113,6 +121,7 @@ public class Context {
      *
      * @return the scope, never null
      */
+    @NonNull
     public EnumSet<Scope> getScope() {
         return mScope;
     }
@@ -122,6 +131,7 @@ public class Context {
      *
      * @return the configuration, never null
      */
+    @NonNull
     public Configuration getConfiguration() {
         return mConfiguration;
     }
@@ -131,6 +141,7 @@ public class Context {
      *
      * @return the project, never null
      */
+    @NonNull
     public Project getProject() {
         return mProject;
     }
@@ -142,6 +153,7 @@ public class Context {
      *
      * @return the main project, never null
      */
+    @NonNull
     public Project getMainProject() {
         return mMainProject != null ? mMainProject : mProject;
     }
@@ -151,6 +163,7 @@ public class Context {
      *
      * @return the client, never null
      */
+    @NonNull
     public LintClient getClient() {
         return mClient;
     }
@@ -163,6 +176,7 @@ public class Context {
      *
      * @return the contents of the given file, or null if an error occurs.
      */
+    @Nullable
     public String getContents() {
         if (mContents == null) {
             mContents = mClient.readFile(file);
@@ -177,6 +191,7 @@ public class Context {
      * @param name the name of the property
      * @return the corresponding value, or null
      */
+    @Nullable
     public Object getProperty(String name) {
         if (mProperties == null) {
             return null;
@@ -191,12 +206,17 @@ public class Context {
      * @param name the name of the property
      * @param value the corresponding value
      */
-    public void setProperty(String name, Object value) {
-        if (mProperties == null) {
-            mProperties = new HashMap<String, Object>();
+    public void setProperty(@NonNull String name, @Nullable Object value) {
+        if (value == null) {
+            if (mProperties != null) {
+                mProperties.remove(name);
+            }
+        } else {
+            if (mProperties == null) {
+                mProperties = new HashMap<String, Object>();
+            }
+            mProperties.put(name, value);
         }
-
-        mProperties.put(name, value);
     }
 
     /**
@@ -204,6 +224,7 @@ public class Context {
      *
      * @return the SDK info for the current project, never null
      */
+    @NonNull
     public SdkInfo getSdkInfo() {
         if (mSdkInfo == null) {
             mSdkInfo = mClient.getSdkInfo(mProject);
@@ -221,7 +242,7 @@ public class Context {
      * @param issue the issue to check
      * @return false if the issue has been disabled
      */
-    public boolean isEnabled(Issue issue) {
+    public boolean isEnabled(@NonNull Issue issue) {
         return mConfiguration.isEnabled(issue);
     }
 
@@ -233,7 +254,11 @@ public class Context {
      * @param message the message for this warning
      * @param data any associated data, or null
      */
-    public void report(Issue issue, Location location, String message, Object data) {
+    public void report(
+            @NonNull Issue issue,
+            @Nullable Location location,
+            @NonNull String message,
+            @Nullable Object data) {
         mClient.report(this, issue, location, message, data);
     }
 
@@ -241,10 +266,13 @@ public class Context {
      * Send an exception to the log. Convenience wrapper around {@link LintClient#log}.
      *
      * @param exception the exception, possibly null
-     * @param format the error message using {@link String#format} syntax
+     * @param format the error message using {@link String#format} syntax, possibly null
      * @param args any arguments for the format string
      */
-    public void log(Throwable exception, String format, Object... args) {
+    public void log(
+            @Nullable Throwable exception,
+            @Nullable String format,
+            @Nullable Object... args) {
         mClient.log(exception, format, args);
     }
 
diff --git a/lint/libs/lint_api/src/com/android/tools/lint/detector/api/Detector.java b/lint/libs/lint_api/src/com/android/tools/lint/detector/api/Detector.java
index 674b71a..40fe554 100644
--- a/lint/libs/lint_api/src/com/android/tools/lint/detector/api/Detector.java
+++ b/lint/libs/lint_api/src/com/android/tools/lint/detector/api/Detector.java
@@ -16,6 +16,8 @@
 
 package com.android.tools.lint.detector.api;
 
+import com.android.annotations.NonNull;
+import com.android.annotations.Nullable;
 import com.google.common.annotations.Beta;
 
 import org.objectweb.asm.tree.ClassNode;
@@ -74,7 +76,8 @@ public abstract class Detector {
          * @param context the {@link Context} for the file being analyzed
          * @return a visitor, or null.
          */
-        AstVisitor createJavaVisitor(JavaContext context);
+        @Nullable
+        AstVisitor createJavaVisitor(@NonNull JavaContext context);
 
         /**
          * Return the types of AST nodes that the visitor returned from
@@ -94,6 +97,7 @@ public abstract class Detector {
          *
          * @return the list of applicable node types (AST node classes), or null
          */
+        @Nullable
         List<Class<? extends lombok.ast.Node>> getApplicableNodeTypes();
 
         /**
@@ -115,6 +119,7 @@ public abstract class Detector {
          *
          * @return a set of applicable method names, or null.
          */
+        @Nullable
         List<String> getApplicableMethodNames();
 
         /**
@@ -131,7 +136,10 @@ public abstract class Detector {
          *            {@link #createJavaVisitor(JavaContext)}, or null
          * @param node the {@link MethodInvocation} node for the invoked method
          */
-        void visitMethod(JavaContext context, AstVisitor visitor, MethodInvocation node);
+        void visitMethod(
+                @NonNull JavaContext context,
+                @Nullable AstVisitor visitor,
+                @NonNull MethodInvocation node);
 
         /**
          * Returns whether this detector cares about Android resource references
@@ -160,8 +168,12 @@ public abstract class Detector {
          * @param name the resource name, such as "main" from
          *            {@code R.layout.main}
          */
-        void visitResourceReference(JavaContext context, AstVisitor visitor,
-                VariableReference node, String type, String name);
+        void visitResourceReference(
+                @NonNull JavaContext context,
+                @Nullable AstVisitor visitor,
+                @NonNull VariableReference node,
+                @NonNull String type,
+                @NonNull String name);
     }
 
     /** Specialized interface for detectors that scan Java class files */
@@ -173,7 +185,7 @@ public abstract class Detector {
          *            the file
          * @param classNode the root class node
          */
-        void checkClass(ClassContext context, ClassNode classNode);
+        void checkClass(@NonNull ClassContext context, @NonNull ClassNode classNode);
     }
 
     /** Specialized interface for detectors that scan XML files */
@@ -184,28 +196,28 @@ public abstract class Detector {
          * @param context information about the document being analyzed
          * @param document the document to examine
          */
-        void visitDocument(XmlContext context, Document document);
+        void visitDocument(@NonNull XmlContext context, @NonNull Document document);
 
         /**
          * Visit the given element.
          * @param context information about the document being analyzed
          * @param element the element to examine
          */
-        void visitElement(XmlContext context, Element element);
+        void visitElement(@NonNull XmlContext context, @NonNull Element element);
 
         /**
          * Visit the given element after its children have been analyzed.
          * @param context information about the document being analyzed
          * @param element the element to examine
          */
-        void visitElementAfter(XmlContext context, Element element);
+        void visitElementAfter(@NonNull XmlContext context, @NonNull Element element);
 
         /**
          * Visit the given attribute.
          * @param context information about the document being analyzed
          * @param attribute the attribute node to examine
          */
-        void visitAttribute(XmlContext context, Attr attribute);
+        void visitAttribute(@NonNull XmlContext context, @NonNull Attr attribute);
 
         /**
          * Returns the list of elements that this detector wants to analyze. If non
@@ -219,6 +231,7 @@ public abstract class Detector {
          *         {@link XmlScanner#ALL} marker to indicate that every single
          *         element should be analyzed.
          */
+        @Nullable
         Collection<String> getApplicableElements();
 
         /**
@@ -233,6 +246,7 @@ public abstract class Detector {
          *         {@link XmlScanner#ALL} marker to indicate that every single
          *         attribute should be analyzed.
          */
+        @Nullable
         Collection<String> getApplicableAttributes();
 
         /**
@@ -240,7 +254,9 @@ public abstract class Detector {
          * {@link #getApplicableAttributes()} to indicate that the check should be
          * invoked on all elements or all attributes
          */
-        public static final List<String> ALL = new ArrayList<String>(0);
+        @NonNull
+        public static final List<String> ALL = new ArrayList<String>(0); // NOT Collections.EMPTY!
+        // We want to distinguish this from just an *empty* list returned by the caller!
     }
 
     /**
@@ -251,7 +267,7 @@ public abstract class Detector {
      *
      * @param context the context describing the work to be done
      */
-    public void run(Context context) {
+    public void run(@NonNull Context context) {
     }
 
     /**
@@ -261,7 +277,7 @@ public abstract class Detector {
      * @param file the file in the context to check
      * @return true if this detector applies to the given context and file
      */
-    public boolean appliesTo(Context context, File file) {
+    public boolean appliesTo(@NonNull Context context, @NonNull File file) {
         return false;
     }
 
@@ -271,7 +287,7 @@ public abstract class Detector {
      * @param context the context for the check referencing the project, lint
      *            client, etc
      */
-    public void beforeCheckProject(Context context) {
+    public void beforeCheckProject(@NonNull Context context) {
     }
 
     /**
@@ -281,7 +297,7 @@ public abstract class Detector {
      * @param context the context for the check referencing the project, lint
      *            client, etc
      */
-    public void afterCheckProject(Context context) {
+    public void afterCheckProject(@NonNull Context context) {
     }
 
     /**
@@ -290,7 +306,7 @@ public abstract class Detector {
      * @param context the context for the check referencing the project, lint
      *            client, etc
      */
-    public void beforeCheckLibraryProject(Context context) {
+    public void beforeCheckLibraryProject(@NonNull Context context) {
     }
 
     /**
@@ -300,7 +316,7 @@ public abstract class Detector {
      * @param context the context for the check referencing the project, lint
      *            client, etc
      */
-    public void afterCheckLibraryProject(Context context) {
+    public void afterCheckLibraryProject(@NonNull Context context) {
     }
 
     /**
@@ -310,7 +326,7 @@ public abstract class Detector {
      * @param context the context for the check referencing the file to be
      *            checked, the project, etc.
      */
-    public void beforeCheckFile(Context context) {
+    public void beforeCheckFile(@NonNull Context context) {
     }
 
     /**
@@ -320,7 +336,7 @@ public abstract class Detector {
      * @param context the context for the check referencing the file to be
      *            checked, the project, etc.
      */
-    public void afterCheckFile(Context context) {
+    public void afterCheckFile(@NonNull Context context) {
     }
 
     /**
@@ -328,12 +344,13 @@ public abstract class Detector {
      *
      * @return the expected speed of this detector
      */
+    @NonNull
     public abstract Speed getSpeed();
 
     // ---- Dummy implementations to make implementing XmlScanner easier: ----
 
     @SuppressWarnings("javadoc")
-    public void visitDocument(XmlContext context, Document document) {
+    public void visitDocument(@NonNull XmlContext context, @NonNull Document document) {
         // This method must be overridden if your detector does
         // not return something from getApplicableElements or
         // getApplicableATtributes
@@ -341,28 +358,30 @@ public abstract class Detector {
     }
 
     @SuppressWarnings("javadoc")
-    public void visitElement(XmlContext context, Element element) {
+    public void visitElement(@NonNull XmlContext context, @NonNull Element element) {
         // This method must be overridden if your detector returns
         // tag names from getApplicableElements
         assert false;
     }
 
     @SuppressWarnings("javadoc")
-    public void visitElementAfter(XmlContext context, Element element) {
+    public void visitElementAfter(@NonNull XmlContext context, @NonNull Element element) {
     }
 
     @SuppressWarnings("javadoc")
-    public void visitAttribute(XmlContext context, Attr attribute) {
+    public void visitAttribute(@NonNull XmlContext context, @NonNull Attr attribute) {
         // This method must be overridden if your detector returns
         // attribute names from getApplicableAttributes
         assert false;
     }
 
     @SuppressWarnings("javadoc")
+    @Nullable
     public Collection<String> getApplicableElements() {
         return null;
     }
 
+    @Nullable
     @SuppressWarnings("javadoc")
     public Collection<String> getApplicableAttributes() {
         return null;
@@ -370,23 +389,24 @@ public abstract class Detector {
 
     // ---- Dummy implementations to make implementing JavaScanner easier: ----
 
-    @SuppressWarnings("javadoc")
+    @Nullable @SuppressWarnings("javadoc")
     public List<String> getApplicableMethodNames() {
         return null;
     }
 
-    @SuppressWarnings("javadoc")
-    public AstVisitor createJavaVisitor(JavaContext context) {
+    @Nullable @SuppressWarnings("javadoc")
+    public AstVisitor createJavaVisitor(@NonNull JavaContext context) {
         return null;
     }
 
-    @SuppressWarnings("javadoc")
+    @Nullable @SuppressWarnings("javadoc")
     public List<Class<? extends lombok.ast.Node>> getApplicableNodeTypes() {
         return null;
     }
 
     @SuppressWarnings("javadoc")
-    public void visitMethod(JavaContext context, AstVisitor visitor, MethodInvocation node) {
+    public void visitMethod(@NonNull JavaContext context, @Nullable AstVisitor visitor,
+            @NonNull MethodInvocation node) {
     }
 
     @SuppressWarnings("javadoc")
@@ -395,14 +415,13 @@ public abstract class Detector {
     }
 
     @SuppressWarnings("javadoc")
-    public void visitResourceReference(JavaContext context, AstVisitor visitor,
-            VariableReference node, String type, String name) {
+    public void visitResourceReference(@NonNull JavaContext context, @Nullable AstVisitor visitor,
+            @NonNull VariableReference node, @NonNull String type, @NonNull String name) {
     }
 
     // ---- Dummy implementations to make implementing a ClassScanner easier: ----
 
     @SuppressWarnings("javadoc")
-    public void checkClass(ClassContext context, ClassNode classNode) {
-
+    public void checkClass(@NonNull ClassContext context, @NonNull ClassNode classNode) {
     }
 }
diff --git a/lint/libs/lint_api/src/com/android/tools/lint/detector/api/Issue.java b/lint/libs/lint_api/src/com/android/tools/lint/detector/api/Issue.java
index fd1ae3d..3e49bc4 100644
--- a/lint/libs/lint_api/src/com/android/tools/lint/detector/api/Issue.java
+++ b/lint/libs/lint_api/src/com/android/tools/lint/detector/api/Issue.java
@@ -16,6 +16,8 @@
 
 package com.android.tools.lint.detector.api;
 
+import com.android.annotations.NonNull;
+import com.android.annotations.Nullable;
 import com.android.tools.lint.client.api.Configuration;
 import com.google.common.annotations.Beta;
 
@@ -48,9 +50,15 @@ public final class Issue implements Comparable<Issue> {
     private final Class<? extends Detector> mClass;
 
     // Use factory methods
-    private Issue(String id, String description, String explanation, Category category,
-            int priority, Severity severity, Class<? extends Detector> detectorClass,
-            EnumSet<Scope> scope) {
+    private Issue(
+            @NonNull String id,
+            @NonNull String description,
+            @NonNull String explanation,
+            @NonNull Category category,
+            int priority,
+            @NonNull Severity severity,
+            @NonNull Class<? extends Detector> detectorClass,
+            @NonNull EnumSet<Scope> scope) {
         super();
         mId = id;
         mDescription = description;
@@ -77,9 +85,16 @@ public final class Issue implements Comparable<Issue> {
      * @param scope the scope of files required to analyze this issue
      * @return a new {@link Issue}
      */
-    public static Issue create(String id, String description, String explanation,
-            Category category, int priority, Severity severity,
-            Class<? extends Detector> detectorClass, EnumSet<Scope> scope) {
+    @NonNull
+    public static Issue create(
+            @NonNull String id,
+            @NonNull String description,
+            @NonNull String explanation,
+            @NonNull Category category,
+            int priority,
+            @NonNull Severity severity,
+            @NonNull Class<? extends Detector> detectorClass,
+            @NonNull EnumSet<Scope> scope) {
         return new Issue(id, description, explanation, category, priority, severity,
                 detectorClass, scope);
     }
@@ -91,6 +106,7 @@ public final class Issue implements Comparable<Issue> {
      *
      * @return the associated fixed id, never null and always unique
      */
+    @NonNull
     public String getId() {
         return mId;
     }
@@ -100,6 +116,7 @@ public final class Issue implements Comparable<Issue> {
      *
      * @return a quick summary of the issue, never null
      */
+    @NonNull
     public String getDescription() {
         return mDescription;
     }
@@ -112,15 +129,17 @@ public final class Issue implements Comparable<Issue> {
      *
      * @return an explanation of the issue, never null.
      */
+    @NonNull
     public String getExplanation() {
         return mExplanation;
     }
 
     /**
-     * The category, or null if no category has been assigned
+     * The primary category of the issue
      *
-     * @return the category, or null if no category has been assigned
+     * @return the primary category of the issue, never null
      */
+    @NonNull
     public Category getCategory() {
         return mCategory;
     }
@@ -150,6 +169,7 @@ public final class Issue implements Comparable<Issue> {
      *
      * @return the severity of the issues found by this detector
      */
+    @NonNull
     public Severity getDefaultSeverity() {
         return mSeverity;
     }
@@ -159,6 +179,7 @@ public final class Issue implements Comparable<Issue> {
      *
      * @return a link to more information, or null
      */
+    @Nullable
     public String getMoreInfo() {
         return mMoreInfoUrl;
     }
@@ -179,6 +200,7 @@ public final class Issue implements Comparable<Issue> {
      *
      * @return the required scope
      */
+    @NonNull
     public EnumSet<Scope> getScope() {
         return mScope;
     }
@@ -193,7 +215,7 @@ public final class Issue implements Comparable<Issue> {
      * @param other the {@link Issue} to compare this issue to
      */
     @Override
-    public int compareTo(Issue other) {
+    public int compareTo(@NonNull Issue other) {
         return getId().compareTo(other.getId());
     }
 
@@ -203,7 +225,8 @@ public final class Issue implements Comparable<Issue> {
      * @param moreInfoUrl url string
      * @return this, for constructor chaining
      */
-    public Issue setMoreInfo(String moreInfoUrl) {
+    @NonNull
+    public Issue setMoreInfo(@NonNull String moreInfoUrl) {
         mMoreInfoUrl = moreInfoUrl;
         return this;
     }
@@ -214,6 +237,7 @@ public final class Issue implements Comparable<Issue> {
      * @param enabledByDefault whether the issue should be enabled by default
      * @return this, for constructor chaining
      */
+    @NonNull
     public Issue setEnabledByDefault(boolean enabledByDefault) {
         mEnabledByDefault = enabledByDefault;
         return this;
@@ -224,6 +248,7 @@ public final class Issue implements Comparable<Issue> {
      *
      * @return the class of the detector to use to find this issue
      */
+    @NonNull
     public Class<? extends Detector> getDetectorClass() {
         return mClass;
     }
diff --git a/lint/libs/lint_api/src/com/android/tools/lint/detector/api/JavaContext.java b/lint/libs/lint_api/src/com/android/tools/lint/detector/api/JavaContext.java
index 2d360d2..b14b4ab 100644
--- a/lint/libs/lint_api/src/com/android/tools/lint/detector/api/JavaContext.java
+++ b/lint/libs/lint_api/src/com/android/tools/lint/detector/api/JavaContext.java
@@ -16,6 +16,8 @@
 
 package com.android.tools.lint.detector.api;
 
+import com.android.annotations.NonNull;
+import com.android.annotations.Nullable;
 import com.android.tools.lint.client.api.IJavaParser;
 import com.android.tools.lint.client.api.LintClient;
 
@@ -50,8 +52,12 @@ public class JavaContext extends Context {
      * @param file the file to be analyzed
      * @param scope the scope used for analysis
      */
-    public JavaContext(LintClient client, Project project, Project main, File file,
-            EnumSet<Scope> scope) {
+    public JavaContext(
+            @NonNull LintClient client,
+            @NonNull Project project,
+            @Nullable Project main,
+            @NonNull File file,
+            @NonNull EnumSet<Scope> scope) {
         super(client, project, main, file, scope);
     }
 
@@ -61,7 +67,8 @@ public class JavaContext extends Context {
      * @param node the AST node to get a location for
      * @return a location for the given node
      */
-    public Location getLocation(Node node) {
+    @NonNull
+    public Location getLocation(@NonNull Node node) {
         if (parser != null) {
             return parser.getLocation(this, node);
         }
diff --git a/lint/libs/lint_api/src/com/android/tools/lint/detector/api/LayoutDetector.java b/lint/libs/lint_api/src/com/android/tools/lint/detector/api/LayoutDetector.java
index c74b92a..c61d7c2 100644
--- a/lint/libs/lint_api/src/com/android/tools/lint/detector/api/LayoutDetector.java
+++ b/lint/libs/lint_api/src/com/android/tools/lint/detector/api/LayoutDetector.java
@@ -27,6 +27,7 @@ import static com.android.tools.lint.detector.api.LintConstants.ATTR_PADDING_TOP
 import static com.android.tools.lint.detector.api.LintConstants.VALUE_FILL_PARENT;
 import static com.android.tools.lint.detector.api.LintConstants.VALUE_MATCH_PARENT;
 
+import com.android.annotations.NonNull;
 import com.android.resources.ResourceFolderType;
 import com.google.common.annotations.Beta;
 
@@ -42,24 +43,24 @@ import org.w3c.dom.Element;
 @Beta
 public abstract class LayoutDetector extends ResourceXmlDetector {
     @Override
-    public boolean appliesTo(ResourceFolderType folderType) {
+    public boolean appliesTo(@NonNull ResourceFolderType folderType) {
         return folderType == ResourceFolderType.LAYOUT;
     }
 
-    private static boolean isFillParent(Element element, String dimension) {
+    private static boolean isFillParent(@NonNull Element element, @NonNull String dimension) {
         String width = element.getAttributeNS(ANDROID_URI, dimension);
         return width.equals(VALUE_MATCH_PARENT) || width.equals(VALUE_FILL_PARENT);
     }
 
-    protected static boolean isWidthFillParent(Element element) {
+    protected static boolean isWidthFillParent(@NonNull Element element) {
         return isFillParent(element, ATTR_LAYOUT_WIDTH);
     }
 
-    protected static boolean isHeightFillParent(Element element) {
+    protected static boolean isHeightFillParent(@NonNull Element element) {
         return isFillParent(element, ATTR_LAYOUT_HEIGHT);
     }
 
-    protected boolean hasPadding(Element root) {
+    protected boolean hasPadding(@NonNull Element root) {
         return root.hasAttributeNS(ANDROID_URI, ATTR_PADDING)
                 || root.hasAttributeNS(ANDROID_URI, ATTR_PADDING_LEFT)
                 || root.hasAttributeNS(ANDROID_URI, ATTR_PADDING_RIGHT)
diff --git a/lint/libs/lint_api/src/com/android/tools/lint/detector/api/LintUtils.java b/lint/libs/lint_api/src/com/android/tools/lint/detector/api/LintUtils.java
index f6cfcba..69cb591 100644
--- a/lint/libs/lint_api/src/com/android/tools/lint/detector/api/LintUtils.java
+++ b/lint/libs/lint_api/src/com/android/tools/lint/detector/api/LintUtils.java
@@ -20,6 +20,8 @@ import static com.android.tools.lint.detector.api.LintConstants.DOT_XML;
 import static com.android.tools.lint.detector.api.LintConstants.ID_RESOURCE_PREFIX;
 import static com.android.tools.lint.detector.api.LintConstants.NEW_ID_RESOURCE_PREFIX;
 
+import com.android.annotations.NonNull;
+import com.android.annotations.Nullable;
 import com.android.resources.FolderTypeRelationship;
 import com.android.resources.ResourceFolderType;
 import com.android.resources.ResourceType;
@@ -50,7 +52,8 @@ public class LintUtils {
      * @param maxItems the maximum number of items to print
      * @return a comma separated list
      */
-    public static String formatList(List<String> strings, int maxItems) {
+    @NonNull
+    public static String formatList(@NonNull List<String> strings, int maxItems) {
         StringBuilder sb = new StringBuilder(20 * strings.size());
 
         for (int i = 0, n = strings.size(); i < n; i++) {
@@ -75,7 +78,7 @@ public class LintUtils {
      * @param type the resource type to check
      * @return true if the given type corresponds to a file-type resource
      */
-    public static boolean isFileBasedResourceType(ResourceType type) {
+    public static boolean isFileBasedResourceType(@NonNull ResourceType type) {
         List<ResourceFolderType> folderTypes = FolderTypeRelationship.getRelatedFolders(type);
         for (ResourceFolderType folderType : folderTypes) {
             if (folderType != ResourceFolderType.VALUES) {
@@ -94,7 +97,7 @@ public class LintUtils {
      * @param file the file to be checked
      * @return true if the given file is an xml file
      */
-    public static boolean isXmlFile(File file) {
+    public static boolean isXmlFile(@NonNull File file) {
         String string = file.getName();
         return string.regionMatches(true, string.length() - DOT_XML.length(),
                 DOT_XML, 0, DOT_XML.length());
@@ -109,7 +112,7 @@ public class LintUtils {
      * @return true if {@code string} ends with {@code suffix},
      *         case-insensitively.
      */
-    public static boolean endsWith(String string, String suffix) {
+    public static boolean endsWith(@NonNull String string, @NonNull String suffix) {
         return string.regionMatches(true /* ignoreCase */, string.length() - suffix.length(),
                 suffix, 0, suffix.length());
     }
@@ -120,7 +123,7 @@ public class LintUtils {
      * @param fileName the file name to extract the basename from
      * @return the basename (the filename without the file extension)
      */
-    public static String getBaseName(String fileName) {
+    public static String getBaseName(@NonNull String fileName) {
         int extension = fileName.indexOf('.');
         if (extension > 0) {
             return fileName.substring(0, extension);
@@ -135,7 +138,8 @@ public class LintUtils {
      * @param node the parent node
      * @return a list of element children, never null
      */
-    public static List<Element> getChildren(Node node) {
+    @NonNull
+    public static List<Element> getChildren(@NonNull Node node) {
         NodeList childNodes = node.getChildNodes();
         List<Element> children = new ArrayList<Element>(childNodes.getLength());
         for (int i = 0, n = childNodes.getLength(); i < n; i++) {
@@ -154,7 +158,7 @@ public class LintUtils {
      * @param node the parent node
      * @return the count of element children
      */
-    public static int getChildCount(Node node) {
+    public static int getChildCount(@NonNull Node node) {
         NodeList childNodes = node.getChildNodes();
         int childCount = 0;
         for (int i = 0, n = childNodes.getLength(); i < n; i++) {
@@ -173,7 +177,8 @@ public class LintUtils {
      * @param id the id to strip
      * @return the stripped id, never null
      */
-    public static String stripIdPrefix(String id) {
+    @NonNull
+    public static String stripIdPrefix(@Nullable String id) {
         if (id == null) {
             return "";
         } else if (id.startsWith(NEW_ID_RESOURCE_PREFIX)) {
@@ -196,7 +201,7 @@ public class LintUtils {
      * @param t the second string to compare
      * @return the edit distance between the two strings
      */
-    public static int editDistance(String s, String t) {
+    public static int editDistance(@NonNull String s, @NonNull String t) {
         int m = s.length();
         int n = t.length();
         int[][] d = new int[m + 1][n + 1];
diff --git a/lint/libs/lint_api/src/com/android/tools/lint/detector/api/Location.java b/lint/libs/lint_api/src/com/android/tools/lint/detector/api/Location.java
index da79244..4cac0ff 100644
--- a/lint/libs/lint_api/src/com/android/tools/lint/detector/api/Location.java
+++ b/lint/libs/lint_api/src/com/android/tools/lint/detector/api/Location.java
@@ -16,6 +16,8 @@
 
 package com.android.tools.lint.detector.api;
 
+import com.android.annotations.NonNull;
+import com.android.annotations.Nullable;
 import com.google.common.annotations.Beta;
 
 import java.io.File;
@@ -46,10 +48,10 @@ public class Location {
      * @param file the associated file (but see the documentation for
      *            {@link #getFile()} for more information on what the file
      *            represents)
-     * @param start the starting position, never null
+     * @param start the starting position, or null
      * @param end the ending position, or null
      */
-    protected Location(File file, Position start, Position end) {
+    protected Location(@NonNull File file, @Nullable Position start, @Nullable Position end) {
         super();
         this.mFile = file;
         this.mStart = start;
@@ -66,6 +68,7 @@ public class Location {
      *
      * @return the file handle for the location
      */
+    @NonNull
     public File getFile() {
         return mFile;
     }
@@ -73,8 +76,9 @@ public class Location {
     /**
      * The start position of the range
      *
-     * @return the start position of the range, never null
+     * @return the start position of the range, or null
      */
+    @Nullable
     public Position getStart() {
         return mStart;
     }
@@ -84,6 +88,7 @@ public class Location {
      *
      * @return the start position of the range, may be null for an empty range
      */
+    @Nullable
     public Position getEnd() {
         return mEnd;
     }
@@ -94,6 +99,7 @@ public class Location {
      *
      * @return a secondary location or null
      */
+    @Nullable
     public Location getSecondary() {
         return mSecondary;
     }
@@ -103,7 +109,7 @@ public class Location {
      *
      * @param secondary a secondary location associated with this location
      */
-    public void setSecondary(Location secondary) {
+    public void setSecondary(@NonNull Location secondary) {
         this.mSecondary = secondary;
     }
 
@@ -117,7 +123,7 @@ public class Location {
      *
      * @param message the message to apply to this location
      */
-    public void setMessage(String message) {
+    public void setMessage(@NonNull String message) {
         mMessage = message;
     }
 
@@ -132,6 +138,7 @@ public class Location {
      *
      * @return the custom message for this location, or null
      */
+    @Nullable
     public String getMessage() {
         return mMessage;
     }
@@ -142,7 +149,8 @@ public class Location {
      * @param file the file to create a location for
      * @return a new location
      */
-    public static Location create(File file) {
+    @NonNull
+    public static Location create(@NonNull File file) {
         return new Location(file, null /*start*/, null /*end*/);
     }
 
@@ -155,7 +163,11 @@ public class Location {
      * @param end the ending position
      * @return a new location
      */
-    public static Location create(File file, Position start, Position end) {
+    @NonNull
+    public static Location create(
+            @NonNull File file,
+            @NonNull Position start,
+            @NonNull Position end) {
         return new Location(file, start, end);
     }
 
@@ -169,7 +181,12 @@ public class Location {
      * @param endOffset the ending offset
      * @return a new location
      */
-    public static Location create(File file, String contents, int startOffset, int endOffset) {
+    @NonNull
+    public static Location create(
+            @NonNull File file,
+            @Nullable String contents,
+            int startOffset,
+            int endOffset) {
         if (startOffset < 0 || endOffset < startOffset) {
             throw new IllegalArgumentException("Invalid offsets");
         }
@@ -212,7 +229,8 @@ public class Location {
      * @param line the line number (0-based) for the position
      * @return a new location
      */
-    public static Location create(File file, String contents, int line) {
+    @NonNull
+    public static Location create(@NonNull File file, @NonNull String contents, int line) {
         return create(file, contents, line, null, null);
     }
 
@@ -231,8 +249,9 @@ public class Location {
      *            the pattern
      * @return a new location
      */
-    public static Location create(File file, String contents, int line,
-            String patternStart, String patternEnd) {
+    @NonNull
+    public static Location create(@NonNull File file, @NonNull String contents, int line,
+            @Nullable String patternStart, @Nullable String patternEnd) {
         int currentLine = 0;
         int offset = 0;
         while (currentLine < line) {
@@ -284,6 +303,7 @@ public class Location {
          *
          * @return create a location for this handle
          */
+        @NonNull
         Location resolve();
     }
 
@@ -301,7 +321,7 @@ public class Location {
          * @param startOffset the start offset within the file
          * @param endOffset the end offset within the file
          */
-        public DefaultLocationHandle(Context context, int startOffset, int endOffset) {
+        public DefaultLocationHandle(@NonNull Context context, int startOffset, int endOffset) {
             mFile = context.file;
             mContents = context.getContents();
             mStartOffset = startOffset;
@@ -309,6 +329,7 @@ public class Location {
         }
 
         @Override
+        @NonNull
         public Location resolve() {
             return Location.create(mFile, mContents, mStartOffset, mEndOffset);
         }
diff --git a/lint/libs/lint_api/src/com/android/tools/lint/detector/api/Project.java b/lint/libs/lint_api/src/com/android/tools/lint/detector/api/Project.java
index 7303462..32ac071 100644
--- a/lint/libs/lint_api/src/com/android/tools/lint/detector/api/Project.java
+++ b/lint/libs/lint_api/src/com/android/tools/lint/detector/api/Project.java
@@ -26,6 +26,8 @@ import static com.android.tools.lint.detector.api.LintConstants.PROJECT_PROPERTI
 import static com.android.tools.lint.detector.api.LintConstants.TAG_USES_SDK;
 import static com.android.tools.lint.detector.api.LintConstants.VALUE_TRUE;
 
+import com.android.annotations.NonNull;
+import com.android.annotations.Nullable;
 import com.android.tools.lint.client.api.Configuration;
 import com.android.tools.lint.client.api.LintClient;
 import com.google.common.annotations.Beta;
@@ -81,12 +83,19 @@ public class Project {
      * @param referenceDir See {@link #getReferenceDir()}.
      * @return a new {@link Project}
      */
-    public static Project create(LintClient client, File dir, File referenceDir) {
+    @NonNull
+    public static Project create(
+            @NonNull LintClient client,
+            @NonNull  File dir,
+            @NonNull File referenceDir) {
         return new Project(client, dir, referenceDir);
     }
 
     /** Creates a new Project. Use one of the factory methods to create. */
-    private Project(LintClient client, File dir, File referenceDir) {
+    private Project(
+            @NonNull LintClient client,
+            @NonNull File dir,
+            @NonNull File referenceDir) {
         mClient = client;
         mDir = dir;
         mReferenceDir = referenceDir;
@@ -161,7 +170,7 @@ public class Project {
     }
 
     @Override
-    public boolean equals(Object obj) {
+    public boolean equals(@Nullable Object obj) {
         if (this == obj)
             return true;
         if (obj == null)
@@ -183,7 +192,7 @@ public class Project {
      *
      * @param file the file to be checked
      */
-    public void addFile(File file) {
+    public void addFile(@NonNull File file) {
         if (mFiles == null) {
             mFiles = new ArrayList<File>();
         }
@@ -196,6 +205,7 @@ public class Project {
      *
      * @return the subset of files to be checked, or null for the whole project
      */
+    @Nullable
     public List<File> getSubset() {
         return mFiles;
     }
@@ -205,6 +215,7 @@ public class Project {
      *
      * @return a list of source folders to search for .java files
      */
+    @NonNull
     public List<File> getJavaSourceFolders() {
         if (mJavaSourceFolders == null) {
             mJavaSourceFolders = mClient.getJavaSourceFolders(this);
@@ -217,6 +228,7 @@ public class Project {
      * Returns the list of output folders for class files
      * @return a list of output folders to search for .class files
      */
+    @NonNull
     public List<File> getJavaClassFolders() {
         if (mJavaClassFolders == null) {
             mJavaClassFolders = mClient.getJavaClassFolders(this);
@@ -232,7 +244,8 @@ public class Project {
      * @param file the file under this project to check
      * @return the path relative to the reference directory (often the project directory)
      */
-    public String getDisplayPath(File file) {
+    @NonNull
+    public String getDisplayPath(@NonNull File file) {
        String path = file.getPath();
        String referencePath = mReferenceDir.getPath();
        if (path.startsWith(referencePath)) {
@@ -253,7 +266,8 @@ public class Project {
      * @param file the file under this project to check
      * @return the path relative to the project
      */
-    public String getRelativePath(File file) {
+    @NonNull
+    public String getRelativePath(@NonNull File file) {
        String path = file.getPath();
        String referencePath = mDir.getPath();
        if (path.startsWith(referencePath)) {
@@ -273,6 +287,7 @@ public class Project {
      *
      * @return the dir
      */
+    @NonNull
     public File getDir() {
         return mDir;
     }
@@ -286,6 +301,7 @@ public class Project {
      *
      * @return the reference directory, never null
      */
+    @NonNull
     public File getReferenceDir() {
         return mReferenceDir;
     }
@@ -295,6 +311,7 @@ public class Project {
      *
      * @return the configuration associated with this project
      */
+    @NonNull
     public Configuration getConfiguration() {
         if (mConfiguration == null) {
             mConfiguration = mClient.getConfiguration(this);
@@ -307,6 +324,7 @@ public class Project {
      *
      * @return the application package, or null if unknown
      */
+    @Nullable
     public String getPackage() {
         //assert !mLibrary; // Should call getPackage on the master project, not the library
         // Assertion disabled because you might be running lint on a standalone library project.
@@ -345,7 +363,7 @@ public class Project {
      *
      * @param document the DOM document for the manifest XML document
      */
-    public void readManifest(Document document) {
+    public void readManifest(@NonNull Document document) {
         assert !mLibrary; // Should call readManifest on the master project, not the library
         Element root = document.getDocumentElement();
         if (root == null) {
@@ -403,6 +421,7 @@ public class Project {
      * @return the list of library projects referenced by this project, never
      *         null
      */
+    @NonNull
     public List<Project> getDirectLibraries() {
         return mDirectLibraries;
     }
@@ -412,6 +431,7 @@ public class Project {
      *
      * @return the transitive closure of the library projects for this project
      */
+    @NonNull
     public List<Project> getAllLibraries() {
         if (mAllLibraries == null) {
             if (mDirectLibraries.size() == 0) {
@@ -432,7 +452,7 @@ public class Project {
      *
      * @param collection the collection to add the projects into
      */
-    private void addLibraryProjects(Collection<Project> collection) {
+    private void addLibraryProjects(@NonNull Collection<Project> collection) {
         for (Project library : mDirectLibraries) {
             collection.add(library);
             // Recurse
diff --git a/lint/libs/lint_api/src/com/android/tools/lint/detector/api/ResourceXmlDetector.java b/lint/libs/lint_api/src/com/android/tools/lint/detector/api/ResourceXmlDetector.java
index 0c941dd..68685c6 100644
--- a/lint/libs/lint_api/src/com/android/tools/lint/detector/api/ResourceXmlDetector.java
+++ b/lint/libs/lint_api/src/com/android/tools/lint/detector/api/ResourceXmlDetector.java
@@ -16,6 +16,7 @@
 
 package com.android.tools.lint.detector.api;
 
+import com.android.annotations.NonNull;
 import com.android.resources.ResourceFolderType;
 import com.google.common.annotations.Beta;
 
@@ -32,7 +33,7 @@ import java.io.File;
 @Beta
 public abstract class ResourceXmlDetector extends Detector implements Detector.XmlScanner {
     @Override
-    public boolean appliesTo(Context context, File file) {
+    public boolean appliesTo(@NonNull Context context, @NonNull File file) {
         return LintUtils.isXmlFile(file);
     }
 
@@ -46,12 +47,12 @@ public abstract class ResourceXmlDetector extends Detector implements Detector.X
      * @return true if this detector can apply to resources in folders of the
      *         given type
      */
-    public boolean appliesTo(ResourceFolderType folderType) {
+    public boolean appliesTo(@NonNull ResourceFolderType folderType) {
         return true;
     }
 
     @Override
-    public void run(Context context) {
+    public void run(@NonNull Context context) {
         // The infrastructure should never call this method on an xml detector since
         // it will run the various visitors instead
         assert false;
diff --git a/lint/libs/lint_api/src/com/android/tools/lint/detector/api/Scope.java b/lint/libs/lint_api/src/com/android/tools/lint/detector/api/Scope.java
index e095498..5141b16 100644
--- a/lint/libs/lint_api/src/com/android/tools/lint/detector/api/Scope.java
+++ b/lint/libs/lint_api/src/com/android/tools/lint/detector/api/Scope.java
@@ -17,6 +17,7 @@
 package com.android.tools.lint.detector.api;
 
 import com.google.common.annotations.Beta;
+import com.android.annotations.NonNull;
 
 import java.util.EnumSet;
 
@@ -87,7 +88,7 @@ public enum Scope {
      * @param scopes the scope set to check
      * @return true if the scope set references a single file
      */
-    public static boolean checkSingleFile(EnumSet<Scope> scopes) {
+    public static boolean checkSingleFile(@NonNull EnumSet<Scope> scopes) {
         return scopes.size() == 1 &&
                 (scopes.contains(JAVA_FILE)
                         || scopes.contains(CLASS_FILE)
diff --git a/lint/libs/lint_api/src/com/android/tools/lint/detector/api/Severity.java b/lint/libs/lint_api/src/com/android/tools/lint/detector/api/Severity.java
index 27840de..e2add3a 100644
--- a/lint/libs/lint_api/src/com/android/tools/lint/detector/api/Severity.java
+++ b/lint/libs/lint_api/src/com/android/tools/lint/detector/api/Severity.java
@@ -16,6 +16,7 @@
 
 package com.android.tools.lint.detector.api;
 
+import com.android.annotations.NonNull;
 import com.google.common.annotations.Beta;
 
 /**
@@ -50,7 +51,7 @@ public enum Severity {
 
     private String mDisplay;
 
-    private Severity(String display) {
+    private Severity(@NonNull String display) {
         mDisplay = display;
     }
 
@@ -59,6 +60,7 @@ public enum Severity {
      *
      * @return a description of the severity
      */
+    @NonNull
     public String getDescription() {
         return mDisplay;
     }
diff --git a/lint/libs/lint_api/src/com/android/tools/lint/detector/api/Speed.java b/lint/libs/lint_api/src/com/android/tools/lint/detector/api/Speed.java
index 79de400..8c20a19 100644
--- a/lint/libs/lint_api/src/com/android/tools/lint/detector/api/Speed.java
+++ b/lint/libs/lint_api/src/com/android/tools/lint/detector/api/Speed.java
@@ -16,6 +16,7 @@
 
 package com.android.tools.lint.detector.api;
 
+import com.android.annotations.NonNull;
 import com.google.common.annotations.Beta;
 
 /**
@@ -37,7 +38,7 @@ public enum Speed {
 
     private String mDisplayName;
 
-    Speed(String displayName) {
+    Speed(@NonNull String displayName) {
         mDisplayName = displayName;
     }
 
@@ -47,6 +48,7 @@ public enum Speed {
      *
      * @return the description of the speed to display to the user
      */
+    @NonNull
     public String getDisplayName() {
         return mDisplayName;
     }
diff --git a/lint/libs/lint_api/src/com/android/tools/lint/detector/api/XmlContext.java b/lint/libs/lint_api/src/com/android/tools/lint/detector/api/XmlContext.java
index c682cc8..cd2ee3a 100644
--- a/lint/libs/lint_api/src/com/android/tools/lint/detector/api/XmlContext.java
+++ b/lint/libs/lint_api/src/com/android/tools/lint/detector/api/XmlContext.java
@@ -16,6 +16,8 @@
 
 package com.android.tools.lint.detector.api;
 
+import com.android.annotations.NonNull;
+import com.android.annotations.Nullable;
 import com.android.tools.lint.client.api.IDomParser;
 import com.android.tools.lint.client.api.LintClient;
 import com.google.common.annotations.Beta;
@@ -51,8 +53,12 @@ public class XmlContext extends Context {
      * @param file the file being checked
      * @param scope the scope for the lint job
      */
-    public XmlContext(LintClient client, Project project, Project main, File file,
-            EnumSet<Scope> scope) {
+    public XmlContext(
+            @NonNull LintClient client,
+            @NonNull Project project,
+            @Nullable Project main,
+            @NonNull File file,
+            @NonNull EnumSet<Scope> scope) {
         super(client, project, main, file, scope);
     }
 
@@ -62,7 +68,8 @@ public class XmlContext extends Context {
      * @param node the node to look up the location for
      * @return the location for the node
      */
-    public Location getLocation(Node node) {
+    @NonNull
+    public Location getLocation(@NonNull Node node) {
         if (parser != null) {
             return parser.getLocation(this, node);
         }