Add onClick check for lint

This lint check makes sure that if a layout references
android:onClick="foo" then one of the Java classes provide a
        public void foo(View)
method. It also looks for simple typos, and warns if the access
modifiers are not right.

(It also moves some ASM-related utility code out of specific detectors
and into the ClassContext class)

Change-Id: Ifb0820221175a0760b83992f54e99f761b4d7097

9 files changed, 521 insertions, 28 deletions

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 a2899d8..08da20c 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
@@ -24,8 +24,11 @@ import com.android.annotations.Nullable;
 import com.android.tools.lint.client.api.LintDriver;
 import com.google.common.annotations.Beta;
 
+import org.objectweb.asm.Type;
+import org.objectweb.asm.tree.AbstractInsnNode;
 import org.objectweb.asm.tree.ClassNode;
 import org.objectweb.asm.tree.FieldNode;
+import org.objectweb.asm.tree.LineNumberNode;
 import org.objectweb.asm.tree.MethodNode;
 
 import java.io.File;
@@ -223,8 +226,12 @@ public class ClassContext extends Context {
         File sourceFile = getSourceFile();
         if (sourceFile != null) {
             // ASM line numbers are 1-based, and lint line numbers are 0-based
-            return Location.create(sourceFile, getSourceContents(), line - 1,
-                    patternStart, patternEnd);
+            if (line != -1) {
+                return Location.create(sourceFile, getSourceContents(), line - 1,
+                        patternStart, patternEnd);
+            } else {
+                return Location.create(sourceFile);
+            }
         }
 
         return Location.create(file);
@@ -302,4 +309,101 @@ public class ClassContext extends Context {
         }
         report(issue, location, message, data); // also checks the class node
     }
+
+    /**
+     * Finds the line number closest to the given node
+     *
+     * @param node the instruction node to get a line number for
+     * @return the closest line number, or -1 if not known
+     */
+    public static int findLineNumber(AbstractInsnNode node) {
+        AbstractInsnNode curr = node;
+
+        // First search backwards
+        while (curr != null) {
+            if (curr.getType() == AbstractInsnNode.LINE) {
+                return ((LineNumberNode) curr).line;
+            }
+            curr = curr.getPrevious();
+        }
+
+        // Then search forwards
+        curr = node;
+        while (curr != null) {
+            if (curr.getType() == AbstractInsnNode.LINE) {
+                return ((LineNumberNode) curr).line;
+            }
+            curr = curr.getNext();
+        }
+
+        return -1;
+    }
+
+    /**
+     * Finds the line number closest to the given method declaration
+     *
+     * @param node the method node to get a line number for
+     * @return the closest line number, or -1 if not known
+     */
+    public static int findLineNumber(MethodNode node) {
+        if (node.instructions != null && node.instructions.size() > 0) {
+            return findLineNumber(node.instructions.get(0));
+        }
+
+        return -1;
+    }
+
+    /**
+     * Computes a user-readable type signature from the given class owner, name
+     * and description
+     *
+     * @param owner the class name
+     * @param name the method name
+     * @param desc the method description
+     * @return a user-readable string
+     */
+    public static String createSignature(String owner, String name, String desc) {
+        StringBuilder sb = new StringBuilder();
+
+        if (desc != null) {
+            Type returnType = Type.getReturnType(desc);
+            sb.append(getTypeString(returnType));
+            sb.append(' ');
+        }
+
+        if (owner != null) {
+            sb.append(owner.replace('/', '.').replace('$','.'));
+        }
+        if (name != null) {
+            sb.append('#');
+            sb.append(name);
+            if (desc != null) {
+                Type[] argumentTypes = Type.getArgumentTypes(desc);
+                if (argumentTypes != null && argumentTypes.length > 0) {
+                    sb.append('(');
+                    boolean first = true;
+                    for (Type type : argumentTypes) {
+                        if (first) {
+                            first = false;
+                        } else {
+                            sb.append(", ");
+                        }
+                        sb.append(getTypeString(type));
+                    }
+                    sb.append(')');
+                }
+            }
+        }
+
+        return sb.toString();
+    }
+
+    private static String getTypeString(Type type) {
+        String s = type.getClassName();
+        if (s.startsWith("java.lang.")) {           //$NON-NLS-1$
+            s = s.substring("java.lang.".length()); //$NON-NLS-1$
+        }
+
+        return s;
+    }
 }
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 9d9cf6d..371046f 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
@@ -133,6 +133,7 @@ public class LintConstants {
     public static final String ATTR_LABEL = "label";                   //$NON-NLS-1$
     public static final String ATTR_HINT = "hint";                     //$NON-NLS-1$
     public static final String ATTR_PROMPT = "prompt";                 //$NON-NLS-1$
+    public static final String ATTR_ON_CLICK = "onClick";              //$NON-NLS-1$
     public static final String ATTR_INPUT_TYPE = "inputType";          //$NON-NLS-1$
     public static final String ATTR_INPUT_METHOD = "inputMethod";      //$NON-NLS-1$
     public static final String ATTR_LAYOUT_GRAVITY = "layout_gravity"; //$NON-NLS-1$
diff --git a/lint/libs/lint_checks/src/com/android/tools/lint/checks/ApiDetector.java b/lint/libs/lint_checks/src/com/android/tools/lint/checks/ApiDetector.java
index 9e744e4..5e469d9 100644
--- a/lint/libs/lint_checks/src/com/android/tools/lint/checks/ApiDetector.java
+++ b/lint/libs/lint_checks/src/com/android/tools/lint/checks/ApiDetector.java
@@ -39,7 +39,6 @@ import org.objectweb.asm.tree.ClassNode;
 import org.objectweb.asm.tree.FieldInsnNode;
 import org.objectweb.asm.tree.InsnList;
 import org.objectweb.asm.tree.LdcInsnNode;
-import org.objectweb.asm.tree.LineNumberNode;
 import org.objectweb.asm.tree.LocalVariableNode;
 import org.objectweb.asm.tree.MethodInsnNode;
 import org.objectweb.asm.tree.MethodNode;
@@ -328,32 +327,9 @@ public class ApiDetector extends LayoutDetector implements Detector.ClassScanner
         return -1;
     }
 
-    private static int findLineNumber(AbstractInsnNode node) {
-        AbstractInsnNode curr = node;
-
-        // First search backwards
-        while (curr != null) {
-            if (curr.getType() == AbstractInsnNode.LINE) {
-                return ((LineNumberNode) curr).line;
-            }
-            curr = curr.getPrevious();
-        }
-
-        // Then search forwards
-        curr = node;
-        while (curr != null) {
-            if (curr.getType() == AbstractInsnNode.LINE) {
-                return ((LineNumberNode) curr).line;
-            }
-            curr = curr.getNext();
-        }
-
-        return -1;
-    }
-
     private void report(final ClassContext context, String message, AbstractInsnNode node,
             MethodNode method, String patternStart, String patternEnd) {
-        int lineNumber = node != null ? findLineNumber(node) : -1;
+        int lineNumber = node != null ? ClassContext.findLineNumber(node) : -1;
         Location location = context.getLocationForLine(lineNumber, patternStart, patternEnd);
         context.report(UNSUPPORTED, method, location, message, null);
     }
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 e3deb3f..6df3def 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
@@ -53,7 +53,7 @@ public class BuiltinIssueRegistry extends IssueRegistry {
     private static final List<Issue> sIssues;
 
     static {
-        final int initialCapacity = 77;
+        final int initialCapacity = 78;
         List<Issue> issues = new ArrayList<Issue>(initialCapacity);
 
         issues.add(AccessibilityDetector.ISSUE);
@@ -83,6 +83,7 @@ public class BuiltinIssueRegistry extends IssueRegistry {
         issues.add(TooManyViewsDetector.TOO_MANY);
         issues.add(TooManyViewsDetector.TOO_DEEP);
         issues.add(GridLayoutDetector.ISSUE);
+        issues.add(OnClickDetector.ISSUE);
         issues.add(TranslationDetector.EXTRA);
         issues.add(TranslationDetector.MISSING);
         issues.add(HardcodedValuesDetector.ISSUE);
diff --git a/lint/libs/lint_checks/src/com/android/tools/lint/checks/OnClickDetector.java b/lint/libs/lint_checks/src/com/android/tools/lint/checks/OnClickDetector.java
new file mode 100644
index 0000000..47e063e
--- /dev/null
+++ b/lint/libs/lint_checks/src/com/android/tools/lint/checks/OnClickDetector.java
@@ -0,0 +1,246 @@
+/*
+ * Copyright (C) 2012 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.ATTR_ON_CLICK;
+
+import com.android.tools.lint.client.api.LintDriver;
+import com.android.tools.lint.detector.api.Category;
+import com.android.tools.lint.detector.api.ClassContext;
+import com.android.tools.lint.detector.api.Context;
+import com.android.tools.lint.detector.api.Detector.ClassScanner;
+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.google.common.base.Joiner;
+import com.sun.xml.internal.ws.org.objectweb.asm.Opcodes;
+
+import org.objectweb.asm.tree.ClassNode;
+import org.objectweb.asm.tree.MethodNode;
+import org.w3c.dom.Attr;
+import org.w3c.dom.Node;
+
+import java.io.File;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.EnumSet;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+/**
+ * Checks for missing onClick handlers
+ */
+public class OnClickDetector extends LayoutDetector implements ClassScanner {
+    /** Missing onClick handlers */
+    public static final Issue ISSUE = Issue.create(
+            "OnClick", //$NON-NLS-1$
+            "Ensures that onClick attribute values refer to real methods",
+
+            "The onClick attribute value should be the name of a method in this View's context " +
+            "to invoke when the view is clicked. This name must correspond to a public method " +
+            "that takes exactly one parameter of type View.\n" +
+            "\n" +
+            "Must be a string value, using '\\;' to escape characters such as '\\n' or " +
+            "'\\uxxxx' for a unicode character.",
+            Category.CORRECTNESS,
+            10,
+            Severity.ERROR,
+            OnClickDetector.class,
+            EnumSet.of(Scope.ALL_RESOURCE_FILES, Scope.CLASS_FILE));
+
+    private Map<String, Location.Handle> mNames;
+    private Map<String, List<String>> mSimilar;
+    private boolean mHaveBytecode;
+
+    /** Constructs a new {@link OnClickDetector} */
+    public OnClickDetector() {
+    }
+
+    @Override
+    public Speed getSpeed() {
+        return Speed.FAST;
+    }
+
+    @Override
+    public boolean appliesTo(Context context, File file) {
+        return true;
+    }
+
+    @Override
+    public void afterCheckProject(Context context) {
+        if (mNames != null && mNames.size() > 0 && mHaveBytecode) {
+            List<String> names = new ArrayList<String>(mNames.keySet());
+            Collections.sort(names);
+            LintDriver driver = context.getDriver();
+            for (String name : names) {
+                Handle handle = mNames.get(name);
+
+                Object clientData = handle.getClientData();
+                if (clientData instanceof Node) {
+                    if (driver.isSuppressed(ISSUE, (Node) clientData)) {
+                        continue;
+                    }
+                }
+
+                Location location = handle.resolve();
+                String message = String.format(
+                    "Corresponding method handler 'public void %1$s(android.view.View)' not found",
+                    name);
+                List<String> similar = mSimilar != null ? mSimilar.get(name) : null;
+                if (similar != null) {
+                    Collections.sort(similar);
+                    message = message + String.format(" (did you mean %1$s ?)",
+                            Joiner.on(", ").join(similar));
+                }
+                context.report(ISSUE, location, message, null);
+            }
+        }
+    }
+
+    // ---- Implements XmlScanner ----
+
+    @Override
+    public Collection<String> getApplicableAttributes() {
+        return Collections.singletonList(ATTR_ON_CLICK);
+    }
+
+    @Override
+    public void visitAttribute(XmlContext context, Attr attribute) {
+        String value = attribute.getValue();
+        if (value.isEmpty() || value.trim().isEmpty()) {
+            context.report(ISSUE, attribute, context.getLocation(attribute),
+                    "onClick attribute value cannot be empty", null);
+        } else if (!value.equals(value.trim())) {
+            context.report(ISSUE, attribute, context.getLocation(attribute),
+                    "There should be no whitespace around attribute values", null);
+        } else {
+            if (mNames == null) {
+                mNames = new HashMap<String, Location.Handle>();
+            }
+            Handle handle = context.parser.createLocationHandle(context, attribute);
+            handle.setClientData(attribute);
+
+            // Replace unicode characters with the actual value since that's how they
+            // appear in the ASM signatures
+            if (value.contains("\\u")) { //$NON-NLS-1$
+                Pattern pattern = Pattern.compile("\\\\u(\\d\\d\\d\\d)"); //$NON-NLS-1$
+                Matcher matcher = pattern.matcher(value);
+                StringBuilder sb = new StringBuilder(value.length());
+                int remainder = 0;
+                while (matcher.find()) {
+                    sb.append(value.substring(0, matcher.start()));
+                    String unicode = matcher.group(1);
+                    int hex = Integer.parseInt(unicode, 16);
+                    sb.append((char) hex);
+                    remainder = matcher.end();
+                }
+                sb.append(value.substring(remainder));
+                value = sb.toString();
+            }
+
+            mNames.put(value, handle);
+        }
+    }
+
+    // ---- Implements ClassScanner ----
+
+    @SuppressWarnings("rawtypes")
+    @Override
+    public void checkClass(ClassContext context, ClassNode classNode) {
+        if (mNames == null) {
+            // No onClick attributes in the XML files
+            return;
+        }
+
+        mHaveBytecode = true;
+
+        List methodList = classNode.methods;
+        for (Object m : methodList) {
+            MethodNode method = (MethodNode) m;
+            boolean rightArguments = method.desc.equals("(Landroid/view/View;)V"); //$NON-NLS-1$
+            if (!mNames.containsKey(method.name)) {
+                if (rightArguments) {
+                    // See if there's a possible typo instead
+                    for (String n : mNames.keySet()) {
+                        if (LintUtils.editDistance(n, method.name) <= 2) {
+                            recordSimilar(n, classNode, method);
+                            break;
+                        }
+                    }
+                }
+                continue;
+            }
+
+            // TODO: Validate class hierarchy: should extend a context method
+            // Longer term, also validate that it's in a layout that corresponds to
+            // the given activity
+
+            if (rightArguments){
+                // Found: remove from list to be checked
+                mNames.remove(method.name);
+
+                // Make sure the method is public
+                if ((method.access & Opcodes.ACC_PUBLIC) == 0) {
+                    int lineNumber = ClassContext.findLineNumber(method);
+                    Location location = null;
+                    location = context.getLocationForLine(lineNumber, method.name, null);
+                    String message = String.format(
+                            "On click handler %1$s(View) must be public",
+                            method.name);
+                    context.report(ISSUE, location, message, null);
+                } else if ((method.access & Opcodes.ACC_STATIC) != 0) {
+                    int lineNumber = ClassContext.findLineNumber(method);
+                    Location location = null;
+                    location = context.getLocationForLine(lineNumber, method.name, null);
+                    String message = String.format(
+                            "On click handler %1$s(View) should not be static",
+                            method.name);
+                    context.report(ISSUE, location, message, null);
+                }
+
+                if (mNames.isEmpty()) {
+                    mNames = null;
+                    return;
+                }
+            }
+        }
+    }
+
+    private void recordSimilar(String name, ClassNode classNode, MethodNode method) {
+        if (mSimilar == null) {
+            mSimilar = new HashMap<String, List<String>>();
+        }
+        List<String> list = mSimilar.get(name);
+        if (list == null) {
+            list = new ArrayList<String>();
+            mSimilar.put(name, list);
+        }
+
+        String signature = ClassContext.createSignature(classNode.name, method.name, method.desc);
+        list.add(signature);
+    }
+}
diff --git a/lint/libs/lint_checks/tests/src/com/android/tools/lint/checks/OnClickDetectorTest.java b/lint/libs/lint_checks/tests/src/com/android/tools/lint/checks/OnClickDetectorTest.java
new file mode 100644
index 0000000..240e0ce
--- /dev/null
+++ b/lint/libs/lint_checks/tests/src/com/android/tools/lint/checks/OnClickDetectorTest.java
@@ -0,0 +1,54 @@
+/*
+ * Copyright (C) 2012 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 OnClickDetectorTest extends AbstractCheckTest {
+    @Override
+    protected Detector getDetector() {
+        return new OnClickDetector();
+    }
+
+    public void test() throws Exception {
+        assertEquals(
+            "onclick.xml:10: Error: Corresponding method handler 'public void nonexistent(android.view.View)' not found\n" +
+            "onclick.xml:16: Error: Corresponding method handler 'public void wrong1(android.view.View)' not found\n" +
+            "onclick.xml:22: Error: Corresponding method handler 'public void wrong2(android.view.View)' not found\n" +
+            "onclick.xml:28: Error: Corresponding method handler 'public void wrong3(android.view.View)' not found\n" +
+            "onclick.xml:34: Error: Corresponding method handler 'public void wrong4(android.view.View)' not found\n" +
+            "onclick.xml:46: Error: Corresponding method handler 'public void simple_typo(android.view.View)' not found (did you mean test.pkg.OnClickActivity#simple_tyop(Landroid/view/View;)V ?)",
+
+            lintProject(
+                "bytecode/.classpath=>.classpath",
+                "bytecode/AndroidManifest.xml=>AndroidManifest.xml",
+                "res/layout/onclick.xml=>res/layout/onclick.xml",
+                "bytecode/OnClickActivity.java.txt=>src/test/pkg/OnClickActivity.java",
+                "bytecode/OnClickActivity.class.data=>bin/classes/test/pkg/OnClickActivity.class"
+                ));
+    }
+
+    public void testOk() throws Exception {
+        // No onClick attributes
+        assertEquals(
+                "No warnings.",
+
+                lintProject("res/layout/accessibility.xml"));
+    }
+
+}
diff --git a/lint/libs/lint_checks/tests/src/com/android/tools/lint/checks/data/bytecode/OnClickActivity.class.data b/lint/libs/lint_checks/tests/src/com/android/tools/lint/checks/data/bytecode/OnClickActivity.class.data
new file mode 100644
index 0000000..efe894a
--- /dev/null
+++ b/lint/libs/lint_checks/tests/src/com/android/tools/lint/checks/data/bytecode/OnClickActivity.class.data
diff --git a/lint/libs/lint_checks/tests/src/com/android/tools/lint/checks/data/bytecode/OnClickActivity.java.txt b/lint/libs/lint_checks/tests/src/com/android/tools/lint/checks/data/bytecode/OnClickActivity.java.txt
new file mode 100644
index 0000000..44402bd
--- /dev/null
+++ b/lint/libs/lint_checks/tests/src/com/android/tools/lint/checks/data/bytecode/OnClickActivity.java.txt
@@ -0,0 +1,44 @@
+package test.pkg;
+
+import android.app.Activity;
+import android.view.View;
+
+/** Test data for the OnClickDetector */
+public class OnClickActivity extends Activity {
+    // Wrong argument type 1
+    public void wrong1() {
+    }
+
+    // Wrong argument type 2
+    public void wrong2(int i) {
+    }
+
+    // Wrong argument type 3
+    public void wrong3(View view, int i) {
+    }
+
+    // Wrong return type
+    public int wrong4(View view) {
+        return 0;
+    }
+
+    // Wrong modifier (not public)
+    void wrong5(View view) {
+    }
+
+    // Wrong modifier (is static)
+    public static void wrong6(View view) {
+    }
+
+    public void ok(View view) {
+    }
+
+    // Ok: Unicode escapes
+    public void my\u1234method(View view) {
+    }
+
+    // Typo
+    public void simple_tyop(View view) {
+    }
+
+}
diff --git a/lint/libs/lint_checks/tests/src/com/android/tools/lint/checks/data/res/layout/onclick.xml b/lint/libs/lint_checks/tests/src/com/android/tools/lint/checks/data/res/layout/onclick.xml
new file mode 100644
index 0000000..d271a30
--- /dev/null
+++ b/lint/libs/lint_checks/tests/src/com/android/tools/lint/checks/data/res/layout/onclick.xml
@@ -0,0 +1,67 @@
+<?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:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:onClick="nonexistent"
+        android:text="Button" />
+
+    <Button
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:onClick="wrong1"
+        android:text="Button" />
+
+    <Button
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:onClick="wrong2"
+        android:text="Button" />
+
+    <Button
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:onClick="wrong3"
+        android:text="Button" />
+
+    <Button
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:onClick="wrong4"
+        android:text="Button" />
+
+    <Button
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:onClick="wrong5"
+        android:text="Button" />
+
+    <Button
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:onClick="wrong6"
+        android:text="Button" />
+
+    <Button
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:onClick="ok"
+        android:text="Button" />
+
+    <Button
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:onClick="simple_typo"
+        android:text="Button" />
+
+    <Button
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:onClick="my\u1234method"
+        android:text="Button" />
+
+</LinearLayout>