Merge "New lint rule for invalid @+id references"

13 files changed, 536 insertions, 54 deletions

diff --git a/eclipse/plugins/com.android.ide.eclipse.adt/src/com/android/ide/eclipse/adt/AdtUtils.java b/eclipse/plugins/com.android.ide.eclipse.adt/src/com/android/ide/eclipse/adt/AdtUtils.java
index ec6f26a..478593b 100644
--- a/eclipse/plugins/com.android.ide.eclipse.adt/src/com/android/ide/eclipse/adt/AdtUtils.java
+++ b/eclipse/plugins/com.android.ide.eclipse.adt/src/com/android/ide/eclipse/adt/AdtUtils.java
@@ -200,43 +200,6 @@ public class AdtUtils {
     }
 
     /**
-     * Computes the edit distance (number of insertions, deletions or substitutions
-     * to edit one string into the other) between two strings. In particular,
-     * this will compute the Levenshtein distance.
-     * <p>
-     * See http://en.wikipedia.org/wiki/Levenshtein_distance for details.
-     *
-     * @param s the first string to compare
-     * @param t the second string to compare
-     * @return the edit distance between the two strings
-     */
-    public static int editDistance(String s, String t) {
-        int m = s.length();
-        int n = t.length();
-        int[][] d = new int[m + 1][n + 1];
-        for (int i = 0; i <= m; i++) {
-            d[i][0] = i;
-        }
-        for (int j = 0; j <= n; j++) {
-            d[0][j] = j;
-        }
-        for (int j = 1; j <= n; j++) {
-            for (int i = 1; i <= m; i++) {
-                if (s.charAt(i - 1) == t.charAt(j - 1)) {
-                    d[i][j] = d[i - 1][j - 1];
-                } else {
-                    int deletion = d[i - 1][j] + 1;
-                    int insertion = d[i][j - 1] + 1;
-                    int substitution = d[i - 1][j - 1] + 1;
-                    d[i][j] = Math.min(deletion, Math.min(insertion, substitution));
-                }
-            }
-        }
-
-        return d[m][n];
-    }
-
-    /**
      * Returns the current editor (the currently visible and active editor), or null if
      * not found
      *
diff --git a/eclipse/plugins/com.android.ide.eclipse.adt/src/com/android/ide/eclipse/adt/internal/editors/layout/gle2/GraphicalEditorPart.java b/eclipse/plugins/com.android.ide.eclipse.adt/src/com/android/ide/eclipse/adt/internal/editors/layout/gle2/GraphicalEditorPart.java
index 13a3fc4..931eac1 100644
--- a/eclipse/plugins/com.android.ide.eclipse.adt/src/com/android/ide/eclipse/adt/internal/editors/layout/gle2/GraphicalEditorPart.java
+++ b/eclipse/plugins/com.android.ide.eclipse.adt/src/com/android/ide/eclipse/adt/internal/editors/layout/gle2/GraphicalEditorPart.java
@@ -39,7 +39,6 @@ import com.android.ide.common.resources.configuration.FolderConfiguration;
 import com.android.ide.common.sdk.LoadStatus;
 import com.android.ide.eclipse.adt.AdtConstants;
 import com.android.ide.eclipse.adt.AdtPlugin;
-import com.android.ide.eclipse.adt.AdtUtils;
 import com.android.ide.eclipse.adt.internal.editors.AndroidXmlEditor;
 import com.android.ide.eclipse.adt.internal.editors.IPageImageProvider;
 import com.android.ide.eclipse.adt.internal.editors.IconFactory;
@@ -70,6 +69,7 @@ import com.android.resources.ResourceFolderType;
 import com.android.resources.ResourceType;
 import com.android.sdklib.IAndroidTarget;
 import com.android.sdklib.SdkConstants;
+import com.android.tools.lint.detector.api.LintUtils;
 import com.android.util.Pair;
 
 import org.eclipse.core.resources.IFile;
@@ -1651,19 +1651,20 @@ public class GraphicalEditorPart extends EditorPart
 
         // Look for typos and try to match with custom views and android views
         String actualBase = actual.substring(actual.lastIndexOf('.') + 1);
+        int maxDistance = actualBase.length() >= 4 ? 2 : 1;
+
         if (views.size() > 0) {
             for (String suggested : views) {
                 String suggestedBase = suggested.substring(suggested.lastIndexOf('.') + 1);
 
                 String matchWith = compareWithPackage ? suggested : suggestedBase;
-                int maxDistance = actualBase.length() >= 4 ? 2 : 1;
                 if (Math.abs(actualBase.length() - matchWith.length()) > maxDistance) {
                     // The string lengths differ more than the allowed edit distance;
                     // no point in even attempting to compute the edit distance (requires
                     // O(n*m) storage and O(n*m) speed, where n and m are the string lengths)
                     continue;
                 }
-                if (AdtUtils.editDistance(actualBase, matchWith) <= maxDistance) {
+                if (LintUtils.editDistance(actualBase, matchWith) <= maxDistance) {
                     // Suggest this class as a typo for the given class
                     String labelClass = (suggestedBase.equals(actual) || actual.indexOf('.') != -1)
                         ? suggested : suggestedBase;
diff --git a/eclipse/plugins/com.android.ide.eclipse.tests/unittests/com/android/ide/eclipse/adt/AdtUtilsTest.java b/eclipse/plugins/com.android.ide.eclipse.tests/unittests/com/android/ide/eclipse/adt/AdtUtilsTest.java
index 65b374b..1eb1b4a 100644
--- a/eclipse/plugins/com.android.ide.eclipse.tests/unittests/com/android/ide/eclipse/adt/AdtUtilsTest.java
+++ b/eclipse/plugins/com.android.ide.eclipse.tests/unittests/com/android/ide/eclipse/adt/AdtUtilsTest.java
@@ -92,16 +92,4 @@ public class AdtUtilsTest extends TestCase {
         assertSame("Foo", AdtUtils.capitalize("Foo"));
         assertNull(null, AdtUtils.capitalize(null));
     }
-
-    public void testEditDistance() {
-        // editing kitten to sitting has edit distance 3:
-        //   replace k with s
-        //   replace e with i
-        //   append g
-        assertEquals(3, AdtUtils.editDistance("kitten", "sitting"));
-
-        assertEquals(3, AdtUtils.editDistance("saturday", "sunday"));
-        assertEquals(1, AdtUtils.editDistance("button", "bitton"));
-        assertEquals(6, AdtUtils.editDistance("radiobutton", "bitton"));
-    }
 }
diff --git a/lint/libs/lint_api/src/com/android/tools/lint/detector/api/LintConstants.java b/lint/libs/lint_api/src/com/android/tools/lint/detector/api/LintConstants.java
index b0fbef6..5ed2d78 100644
--- a/lint/libs/lint_api/src/com/android/tools/lint/detector/api/LintConstants.java
+++ b/lint/libs/lint_api/src/com/android/tools/lint/detector/api/LintConstants.java
@@ -112,10 +112,12 @@ public class LintConstants {
 
     // Attributes: Resources
     public static final String ATTR_NAME = "name";                     //$NON-NLS-1$
+    public static final String ATTR_TYPE = "type";                     //$NON-NLS-1$
     public static final String ATTR_PARENT = "parent";                 //$NON-NLS-1$
     public static final String ATTR_TRANSLATABLE = "translatable";     //$NON-NLS-1$
 
     // Attributes: Layout
+    public static final String ATTR_LAYOUT_PREFIX = "layout_";         //$NON-NLS-1$
     public static final String ATTR_CLASS = "class";                   //$NON-NLS-1$
     public static final String ATTR_STYLE = "style";                   //$NON-NLS-1$
 
@@ -191,6 +193,9 @@ public class LintConstants {
     public static final String VALUE_MATCH_PARENT = "match_parent";     //$NON-NLS-1$
     public static final String VALUE_VERTICAL = "vertical";             //$NON-NLS-1$
 
+    // Values: Resources
+    public static final String VALUE_ID = "id";                        //$NON-NLS-1$
+
     // Values: Drawables
     public static final String VALUE_DISABLED = "disabled";            //$NON-NLS-1$
     public static final String VALUE_CLAMP = "clamp";                  //$NON-NLS-1$
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 55d1cf6..186a5f3 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
@@ -17,6 +17,8 @@
 package com.android.tools.lint.detector.api;
 
 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.resources.FolderTypeRelationship;
 import com.android.resources.ResourceFolderType;
@@ -149,4 +151,59 @@ public class LintUtils {
 
         return childCount;
     }
+
+    /**
+     * Returns the given id without an {@code @id/} or {@code @+id} prefix
+     *
+     * @param id the id to strip
+     * @return the stripped id, never null
+     */
+    public static String stripIdPrefix(String id) {
+        if (id == null) {
+            return "";
+        } else if (id.startsWith(NEW_ID_RESOURCE_PREFIX)) {
+            return id.substring(NEW_ID_RESOURCE_PREFIX.length());
+        } else if (id.startsWith(ID_RESOURCE_PREFIX)) {
+            return id.substring(ID_RESOURCE_PREFIX.length());
+        }
+
+        return id;
+    }
+
+    /**
+     * Computes the edit distance (number of insertions, deletions or substitutions
+     * to edit one string into the other) between two strings. In particular,
+     * this will compute the Levenshtein distance.
+     * <p>
+     * See http://en.wikipedia.org/wiki/Levenshtein_distance for details.
+     *
+     * @param s the first string to compare
+     * @param t the second string to compare
+     * @return the edit distance between the two strings
+     */
+    public static int editDistance(String s, String t) {
+        int m = s.length();
+        int n = t.length();
+        int[][] d = new int[m + 1][n + 1];
+        for (int i = 0; i <= m; i++) {
+            d[i][0] = i;
+        }
+        for (int j = 0; j <= n; j++) {
+            d[0][j] = j;
+        }
+        for (int j = 1; j <= n; j++) {
+            for (int i = 1; i <= m; i++) {
+                if (s.charAt(i - 1) == t.charAt(j - 1)) {
+                    d[i][j] = d[i - 1][j - 1];
+                } else {
+                    int deletion = d[i - 1][j] + 1;
+                    int insertion = d[i][j - 1] + 1;
+                    int substitution = d[i - 1][j - 1] + 1;
+                    d[i][j] = Math.min(deletion, Math.min(insertion, substitution));
+                }
+            }
+        }
+
+        return d[m][n];
+    }
 }
diff --git a/lint/libs/lint_checks/src/com/android/tools/lint/checks/BuiltinIssueRegistry.java b/lint/libs/lint_checks/src/com/android/tools/lint/checks/BuiltinIssueRegistry.java
index b1644d9..cc2a799 100644
--- a/lint/libs/lint_checks/src/com/android/tools/lint/checks/BuiltinIssueRegistry.java
+++ b/lint/libs/lint_checks/src/com/android/tools/lint/checks/BuiltinIssueRegistry.java
@@ -58,6 +58,8 @@ public class BuiltinIssueRegistry extends IssueRegistry {
         issues.add(FieldGetterDetector.ISSUE);
         issues.add(DuplicateIdDetector.CROSS_LAYOUT);
         issues.add(DuplicateIdDetector.WITHIN_LAYOUT);
+        issues.add(WrongIdDetector.UNKNOWN_ID);
+        issues.add(WrongIdDetector.UNKNOWN_ID_LAYOUT);
         issues.add(StateListDetector.ISSUE);
         issues.add(InefficientWeightDetector.INEFFICIENT_WEIGHT);
         issues.add(InefficientWeightDetector.NESTED_WEIGHTS);
diff --git a/lint/libs/lint_checks/src/com/android/tools/lint/checks/ObsoleteLayoutParamsDetector.java b/lint/libs/lint_checks/src/com/android/tools/lint/checks/ObsoleteLayoutParamsDetector.java
index 487f6b1..685e893 100644
--- a/lint/libs/lint_checks/src/com/android/tools/lint/checks/ObsoleteLayoutParamsDetector.java
+++ b/lint/libs/lint_checks/src/com/android/tools/lint/checks/ObsoleteLayoutParamsDetector.java
@@ -43,6 +43,7 @@ import static com.android.tools.lint.detector.api.LintConstants.ATTR_LAYOUT_MARG
 import static com.android.tools.lint.detector.api.LintConstants.ATTR_LAYOUT_MARGIN_LEFT;
 import static com.android.tools.lint.detector.api.LintConstants.ATTR_LAYOUT_MARGIN_RIGHT;
 import static com.android.tools.lint.detector.api.LintConstants.ATTR_LAYOUT_MARGIN_TOP;
+import static com.android.tools.lint.detector.api.LintConstants.ATTR_LAYOUT_PREFIX;
 import static com.android.tools.lint.detector.api.LintConstants.ATTR_LAYOUT_ROW;
 import static com.android.tools.lint.detector.api.LintConstants.ATTR_LAYOUT_ROW_SPAN;
 import static com.android.tools.lint.detector.api.LintConstants.ATTR_LAYOUT_SPAN;
@@ -233,8 +234,8 @@ public class ObsoleteLayoutParamsDetector extends LayoutDetector {
     @Override
     public void visitAttribute(XmlContext context, Attr attribute) {
         String name = attribute.getLocalName();
-        if (name != null && name.startsWith("layout_") &&                //$NON-NLS-1$
-                ANDROID_URI.equals(attribute.getNamespaceURI())) {
+        if (name != null && name.startsWith(ATTR_LAYOUT_PREFIX)
+                && ANDROID_URI.equals(attribute.getNamespaceURI())) {
             if (VALID.contains(name)) {
                 return;
             }
diff --git a/lint/libs/lint_checks/src/com/android/tools/lint/checks/WrongIdDetector.java b/lint/libs/lint_checks/src/com/android/tools/lint/checks/WrongIdDetector.java
new file mode 100644
index 0000000..15b3e5e
--- /dev/null
+++ b/lint/libs/lint_checks/src/com/android/tools/lint/checks/WrongIdDetector.java
@@ -0,0 +1,335 @@
+/*
+ * Copyright (C) 2011 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.tools.lint.checks;
+
+import static com.android.tools.lint.detector.api.LintConstants.ANDROID_URI;
+import static com.android.tools.lint.detector.api.LintConstants.ATTR_ID;
+import static com.android.tools.lint.detector.api.LintConstants.ATTR_LAYOUT_PREFIX;
+import static com.android.tools.lint.detector.api.LintConstants.ATTR_NAME;
+import static com.android.tools.lint.detector.api.LintConstants.ATTR_TYPE;
+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 static com.android.tools.lint.detector.api.LintConstants.RELATIVE_LAYOUT;
+import static com.android.tools.lint.detector.api.LintConstants.TAG_ITEM;
+import static com.android.tools.lint.detector.api.LintConstants.VALUE_ID;
+import static com.android.tools.lint.detector.api.LintUtils.stripIdPrefix;
+
+import com.android.resources.ResourceFolderType;
+import com.android.tools.lint.client.api.IDomParser;
+import com.android.tools.lint.detector.api.Category;
+import com.android.tools.lint.detector.api.Context;
+import com.android.tools.lint.detector.api.Issue;
+import com.android.tools.lint.detector.api.LayoutDetector;
+import com.android.tools.lint.detector.api.LintUtils;
+import com.android.tools.lint.detector.api.Location;
+import com.android.tools.lint.detector.api.Location.Handle;
+import com.android.tools.lint.detector.api.Scope;
+import com.android.tools.lint.detector.api.Severity;
+import com.android.tools.lint.detector.api.Speed;
+import com.android.tools.lint.detector.api.XmlContext;
+import com.android.util.Pair;
+import com.google.common.base.Joiner;
+import com.google.common.collect.ArrayListMultimap;
+import com.google.common.collect.Multimap;
+import com.google.common.collect.Sets;
+
+import org.w3c.dom.Attr;
+import org.w3c.dom.Element;
+import org.w3c.dom.NamedNodeMap;
+import org.w3c.dom.Node;
+import org.w3c.dom.NodeList;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+
+/**
+ * Checks for duplicate ids within a layout and within an included layout
+ */
+public class WrongIdDetector extends LayoutDetector {
+
+    /** Ids bound to widgets in any of the layout files */
+    private Set<String> mGlobalIds = new HashSet<String>(100);
+
+    /** Ids bound to widgets in the current layout file */
+    private Set<String> mFileIds;
+
+    /** Ids declared in a value's file, e.g. {@code <item type="id" name="foo"/>} */
+    private Set<String> mDeclaredIds;
+
+    /**
+     * Location handles for the various id references that were not found as
+     * defined in the same layout, to be checked after the whole project has
+     * been scanned
+     */
+    private List<Pair<String, Location.Handle>> mHandles;
+
+    /** List of RelativeLayout elements in the current layout */
+    private List<Element> mRelativeLayouts;
+
+    /** Reference to an unknown id */
+    public static final Issue UNKNOWN_ID = Issue.create(
+            "UnknownId", //$NON-NLS-1$
+            "Checks for id references in RelativeLayouts that are not defined elsewhere",
+            "The \"@+id/\" syntax refers to an existing id, or creates a new one if it has " +
+            "not already been defined elsewhere. However, this means that if you have a " +
+            "typo in your reference, or if the referred view no longer exists, you do not " +
+            "get a warning since the id will be created on demand. This check catches " +
+            "errors where you have renamed an id without updating all of the references to " +
+            "it.",
+            Category.CORRECTNESS,
+            8,
+            Severity.ERROR,
+            WrongIdDetector.class,
+            Scope.ALL_RESOURCES_SCOPE);
+
+    /** Reference to an id that is not in the current layout */
+    public static final Issue UNKNOWN_ID_LAYOUT = Issue.create(
+            "UnknownIdInLayout", //$NON-NLS-1$
+            "Makes sure that @+id references refer to views in the same layout",
+
+            "The \"@+id/\" syntax refers to an existing id, or creates a new one if it has " +
+            "not already been defined elsewhere. However, this means that if you have a " +
+            "typo in your reference, or if the referred view no longer exists, you do not " +
+            "get a warning since the id will be created on demand.\n" +
+            "\n" +
+            "This is sometimes intentional, for example where you are referring to a view " +
+            "which is provided in a different layout via an include. However, it is usually " +
+            "an accident where you have a typo or you have renamed a view without updating " +
+            "all the references to it.",
+
+            Category.CORRECTNESS,
+            5,
+            Severity.WARNING,
+            WrongIdDetector.class,
+            Scope.RESOURCE_FILE_SCOPE);
+
+    /** Constructs a duplicate id check */
+    public WrongIdDetector() {
+    };
+
+    @Override
+    public boolean appliesTo(ResourceFolderType folderType) {
+        return folderType == ResourceFolderType.LAYOUT || folderType == ResourceFolderType.VALUES;
+    }
+
+    @Override
+    public Speed getSpeed() {
+        return Speed.FAST;
+    }
+
+    @Override
+    public Collection<String> getApplicableAttributes() {
+        return Collections.singletonList(ATTR_ID);
+    }
+
+    @Override
+    public Collection<String> getApplicableElements() {
+        return Arrays.asList(RELATIVE_LAYOUT, TAG_ITEM);
+    }
+
+    @Override
+    public void beforeCheckFile(Context context) {
+        mFileIds = new HashSet<String>();
+        mRelativeLayouts = null;
+    }
+
+    @Override
+    public void afterCheckFile(Context context) {
+        if (mRelativeLayouts != null) {
+            for (Element layout : mRelativeLayouts) {
+                NodeList children = layout.getChildNodes();
+                for (int j = 0, childCount = children.getLength(); j < childCount; j++) {
+                    Node child = children.item(j);
+                    if (child.getNodeType() != Node.ELEMENT_NODE) {
+                        continue;
+                    }
+                    Element element = (Element) child;
+                    NamedNodeMap attributes = element.getAttributes();
+                    for (int i = 0, n = attributes.getLength(); i < n; i++) {
+                        Attr attr = (Attr) attributes.item(i);
+                        String value = attr.getValue();
+                        if ((value.startsWith(NEW_ID_RESOURCE_PREFIX) ||
+                                value.startsWith(ID_RESOURCE_PREFIX))
+                                && ANDROID_URI.equals(attr.getNamespaceURI())
+                                && attr.getLocalName().startsWith(ATTR_LAYOUT_PREFIX)) {
+                            if (!idDefined(mFileIds, value)) {
+                                // Stash a reference to this id and location such that
+                                // we can check after the *whole* layout has been processed,
+                                // since it's too early to conclude here that the id does
+                                // not exist (you are allowed to have forward references)
+                                XmlContext xmlContext = (XmlContext) context;
+                                IDomParser parser = xmlContext.parser;
+                                Handle handle = parser.createLocationHandle(xmlContext, attr);
+
+                                if (mHandles == null) {
+                                    mHandles = new ArrayList<Pair<String,Handle>>();
+                                }
+                                mHandles.add(Pair.of(value, handle));
+                            }
+                        }
+                    }
+                }
+            }
+        }
+
+        mFileIds = null;
+    }
+
+    @Override
+    public void afterCheckProject(Context context) {
+        if (mHandles != null) {
+            boolean checkSameLayout = context.isEnabled(UNKNOWN_ID_LAYOUT);
+            boolean checkExists = context.isEnabled(UNKNOWN_ID);
+            boolean projectScope = context.getScope().contains(Scope.ALL_RESOURCE_FILES);
+            for (Pair<String, Handle> pair : mHandles) {
+                String id = pair.getFirst();
+                boolean isBound = idDefined(mGlobalIds, id);
+                if (!isBound && checkExists && projectScope) {
+                    Handle handle = pair.getSecond();
+                    Location location = handle.resolve();
+                    boolean isDeclared = idDefined(mDeclaredIds, id);
+                    id = stripIdPrefix(id);
+                    String suggestionMessage;
+                    List<String> suggestions = getSpellingSuggestions(id, mGlobalIds);
+                    if (suggestions.size() > 1) {
+                        suggestionMessage = String.format(" Did you mean one of {%2$s} ?",
+                                id, Joiner.on(", ").join(suggestions));
+                    } else if (suggestions.size() > 0) {
+                        suggestionMessage = String.format(" Did you mean %2$s ?",
+                                id, suggestions.get(0));
+                    } else {
+                        suggestionMessage = "";
+                    }
+                    String message;
+                    if (isDeclared) {
+                        message = String.format(
+                                "The id \"%1$s\" is defined but not assigned to any views.%2$s",
+                                id, suggestionMessage);
+                    } else {
+                        message = String.format(
+                                "The id \"%1$s\" is not defined anywhere.%2$s",
+                                id, suggestionMessage);
+                    }
+                    context.report(UNKNOWN_ID, location, message, null);
+                } else if (checkSameLayout && (!projectScope || isBound)) {
+                    // The id was defined, but in a different layout. Usually not intentional
+                    // (might be referring to a random other view that happens to have the same
+                    // name.)
+                    Handle handle = pair.getSecond();
+                    Location location = handle.resolve();
+                    context.report(UNKNOWN_ID_LAYOUT, location,
+                            String.format(
+                                    "The id \"%1$s\" is not referring to any views in this layout",
+                                    stripIdPrefix(id)),
+                            null);
+                }
+            }
+        }
+    }
+
+    @Override
+    public void visitElement(XmlContext context, Element element) {
+        if (element.getTagName().equals(RELATIVE_LAYOUT)) {
+            if (mRelativeLayouts == null) {
+                mRelativeLayouts = new ArrayList<Element>();
+            }
+            mRelativeLayouts.add(element);
+        } else {
+            assert element.getTagName().equals(TAG_ITEM);
+            String type = element.getAttribute(ATTR_TYPE);
+            if (VALUE_ID.equals(type)) {
+                String name = element.getAttribute(ATTR_NAME);
+                if (name.length() > 0) {
+                    if (mDeclaredIds == null) {
+                        mDeclaredIds = Sets.newHashSet();
+                    }
+                    mDeclaredIds.add(ID_RESOURCE_PREFIX + name);
+                }
+            }
+        }
+    }
+
+    @Override
+    public void visitAttribute(XmlContext context, Attr attribute) {
+        assert attribute.getLocalName().equals(ATTR_ID);
+        String id = attribute.getValue();
+        mFileIds.add(id);
+        mGlobalIds.add(id);
+    }
+
+    private static boolean idDefined(Set<String> ids, String id) {
+        if (ids == null) {
+            return false;
+        }
+        boolean definedLocally = ids.contains(id);
+        if (!definedLocally) {
+            if (id.startsWith(NEW_ID_RESOURCE_PREFIX)) {
+                definedLocally = ids.contains(ID_RESOURCE_PREFIX +
+                        id.substring(NEW_ID_RESOURCE_PREFIX.length()));
+            } else if (id.startsWith(ID_RESOURCE_PREFIX)) {
+                definedLocally = ids.contains(NEW_ID_RESOURCE_PREFIX +
+                        id.substring(ID_RESOURCE_PREFIX.length()));
+            }
+        }
+
+        return definedLocally;
+    }
+
+    private List<String> getSpellingSuggestions(String id, Collection<String> ids) {
+        int maxDistance = id.length() >= 4 ? 2 : 1;
+
+        // Look for typos and try to match with custom views and android views
+        Multimap<Integer, String> matches = ArrayListMultimap.create(2, 10);
+        int count = 0;
+        if (ids.size() > 0) {
+            for (String matchWith : ids) {
+                matchWith = stripIdPrefix(matchWith);
+                if (Math.abs(id.length() - matchWith.length()) > maxDistance) {
+                    // The string lengths differ more than the allowed edit distance;
+                    // no point in even attempting to compute the edit distance (requires
+                    // O(n*m) storage and O(n*m) speed, where n and m are the string lengths)
+                    continue;
+                }
+                int distance = LintUtils.editDistance(id, matchWith);
+                if (distance <= maxDistance) {
+                    matches.put(distance, matchWith);
+                }
+
+                if (count++ > 100) {
+                    // Make sure that for huge projects we don't completely grind to a halt
+                    break;
+                }
+            }
+        }
+
+        for (int i = 0; i < maxDistance; i++) {
+            Collection<String> s = matches.get(i);
+            if (s != null && s.size() > 0) {
+                List<String> suggestions = new ArrayList<String>(s);
+                Collections.sort(suggestions);
+                return suggestions;
+            }
+        }
+
+        return Collections.emptyList();
+    }
+}
diff --git a/lint/libs/lint_checks/tests/src/com/android/tools/lint/checks/WrongIdDetectorTest.java b/lint/libs/lint_checks/tests/src/com/android/tools/lint/checks/WrongIdDetectorTest.java
new file mode 100644
index 0000000..1b14c9b
--- /dev/null
+++ b/lint/libs/lint_checks/tests/src/com/android/tools/lint/checks/WrongIdDetectorTest.java
@@ -0,0 +1,52 @@
+/*
+ * Copyright (C) 2011 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.tools.lint.checks;
+
+import com.android.tools.lint.detector.api.Detector;
+
+@SuppressWarnings("javadoc")
+public class WrongIdDetectorTest extends AbstractCheckTest {
+    @Override
+    protected Detector getDetector() {
+        return new WrongIdDetector();
+    }
+
+    public void test() throws Exception {
+        assertEquals(
+            "layout1.xml:14: Error: The id \"button5\" is not defined anywhere. Did you mean one of {button1, button2, button3, button4} ?\n" +
+            "layout1.xml:15: Warning: The id \"my_id2\" is not referring to any views in this layout\n" +
+            "layout1.xml:17: Error: The id \"my_id3\" is not defined anywhere. Did you mean my_id2 ?\n" +
+            "layout1.xml:18: Error: The id \"my_id1\" is defined but not assigned to any views. Did you mean my_id2 ?",
+
+            lintProject(
+                    "wrongid/layout1.xml=>res/layout/layout1.xml",
+                    "wrongid/layout2.xml=>res/layout/layout2.xml",
+                    "wrongid/ids.xml=>res/values/ids.xml"
+        ));
+    }
+
+    public void testSingleFile() throws Exception {
+        assertEquals(
+            "layout1.xml:14: Warning: The id \"button5\" is not referring to any views in this layout\n" +
+            "layout1.xml:15: Warning: The id \"my_id2\" is not referring to any views in this layout\n" +
+            "layout1.xml:17: Warning: The id \"my_id3\" is not referring to any views in this layout\n" +
+            "layout1.xml:18: Warning: The id \"my_id1\" is not referring to any views in this layout",
+
+            lintFiles("wrongid/layout1.xml=>res/layout/layout1.xml"));
+    }
+
+}
diff --git a/lint/libs/lint_checks/tests/src/com/android/tools/lint/checks/data/wrongid/ids.xml b/lint/libs/lint_checks/tests/src/com/android/tools/lint/checks/data/wrongid/ids.xml
new file mode 100644
index 0000000..07e8ae9
--- /dev/null
+++ b/lint/libs/lint_checks/tests/src/com/android/tools/lint/checks/data/wrongid/ids.xml
@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+
+    <item name="my_id1" type="id"/>
+
+</resources>
diff --git a/lint/libs/lint_checks/tests/src/com/android/tools/lint/checks/data/wrongid/layout1.xml b/lint/libs/lint_checks/tests/src/com/android/tools/lint/checks/data/wrongid/layout1.xml
new file mode 100644
index 0000000..073dddd
--- /dev/null
+++ b/lint/libs/lint_checks/tests/src/com/android/tools/lint/checks/data/wrongid/layout1.xml
@@ -0,0 +1,45 @@
+<?xml version="1.0" encoding="utf-8"?>
+<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    android:id="@+id/RelativeLayout1"
+    android:layout_width="fill_parent"
+    android:layout_height="fill_parent"
+    android:orientation="vertical" >
+
+    <!-- my_id1 is defined in ids.xml, my_id2 is defined in main2, my_id3 does not exist -->
+
+    <Button
+        android:id="@+id/button1"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_alignBottom="@+id/button5"
+        android:layout_alignLeft="@+id/my_id2"
+        android:layout_alignParentTop="true"
+        android:layout_alignRight="@+id/my_id3"
+        android:layout_alignTop="@+id/my_id1"
+        android:text="Button" />
+
+    <Button
+        android:id="@+id/button2"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_alignParentLeft="true"
+        android:layout_below="@+id/button1"
+        android:text="Button" />
+
+    <Button
+        android:id="@+id/button3"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_alignParentLeft="true"
+        android:layout_below="@+id/button2"
+        android:text="Button" />
+
+    <Button
+        android:id="@+id/button4"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_alignParentLeft="true"
+        android:layout_below="@+id/button3"
+        android:text="Button" />
+
+</RelativeLayout>
diff --git a/lint/libs/lint_checks/tests/src/com/android/tools/lint/checks/data/wrongid/layout2.xml b/lint/libs/lint_checks/tests/src/com/android/tools/lint/checks/data/wrongid/layout2.xml
new file mode 100644
index 0000000..54dd91a
--- /dev/null
+++ b/lint/libs/lint_checks/tests/src/com/android/tools/lint/checks/data/wrongid/layout2.xml
@@ -0,0 +1,13 @@
+<?xml version="1.0" encoding="utf-8"?>
+<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    android:orientation="vertical" >
+
+    <Button
+        android:id="@+id/my_id2"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:text="Button" />
+
+</LinearLayout>
diff --git a/lint/libs/lint_checks/tests/src/com/android/tools/lint/detector/api/LintUtilsTest.java b/lint/libs/lint_checks/tests/src/com/android/tools/lint/detector/api/LintUtilsTest.java
index e4c4372..ba3df3b 100644
--- a/lint/libs/lint_checks/tests/src/com/android/tools/lint/detector/api/LintUtilsTest.java
+++ b/lint/libs/lint_checks/tests/src/com/android/tools/lint/detector/api/LintUtilsTest.java
@@ -45,4 +45,18 @@ public class LintUtilsTest extends TestCase {
         assertFalse(LintUtils.isXmlFile(new File("xml")));
         assertFalse(LintUtils.isXmlFile(new File("xml.png")));
     }
+
+    public void testEditDistance() {
+        assertEquals(0, LintUtils.editDistance("kitten", "kitten"));
+
+        // editing kitten to sitting has edit distance 3:
+        //   replace k with s
+        //   replace e with i
+        //   append g
+        assertEquals(3, LintUtils.editDistance("kitten", "sitting"));
+
+        assertEquals(3, LintUtils.editDistance("saturday", "sunday"));
+        assertEquals(1, LintUtils.editDistance("button", "bitton"));
+        assertEquals(6, LintUtils.editDistance("radiobutton", "bitton"));
+    }
 }
\ No newline at end of file