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com.android.tools.lint.checks.ClickableViewAccessibilityDetector Maven / Gradle / Ivy
/*
* Copyright (C) 2014 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.SdkConstants.ANDROID_VIEW_VIEW;
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.ClassContext;
import com.android.tools.lint.detector.api.Detector;
import com.android.tools.lint.detector.api.Implementation;
import com.android.tools.lint.detector.api.Issue;
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 org.objectweb.asm.Opcodes;
import org.objectweb.asm.tree.AbstractInsnNode;
import org.objectweb.asm.tree.ClassNode;
import org.objectweb.asm.tree.InsnList;
import org.objectweb.asm.tree.MethodInsnNode;
import org.objectweb.asm.tree.MethodNode;
import java.util.List;
import java.util.ListIterator;
/**
* Checks that views that override View#onTouchEvent also implement View#performClick
* and call performClick when click detection occurs.
*/
public class ClickableViewAccessibilityDetector extends Detector implements Detector.ClassScanner {
public static final Issue ISSUE = Issue.create(
"ClickableViewAccessibility", //$NON-NLS-1$
"Accessibility in Custom Views",
"If a `View` that overrides `onTouchEvent` or uses an `OnTouchListener` does not also "
+ "implement `performClick` and call it when clicks are detected, the `View` "
+ "may not handle accessibility actions properly. Logic handling the click "
+ "actions should ideally be placed in `View#performClick` as some "
+ "accessibility services invoke `performClick` when a click action "
+ "should occur.",
Category.A11Y,
6,
Severity.WARNING,
new Implementation(
ClickableViewAccessibilityDetector.class,
Scope.CLASS_FILE_SCOPE));
private static final String ON_TOUCH_EVENT = "onTouchEvent"; //$NON-NLS-1$
private static final String ON_TOUCH_EVENT_SIG = "(Landroid/view/MotionEvent;)Z"; //$NON-NLS-1$
private static final String PERFORM_CLICK = "performClick"; //$NON-NLS-1$
private static final String PERFORM_CLICK_SIG = "()Z"; //$NON-NLS-1$
private static final String SET_ON_TOUCH_LISTENER = "setOnTouchListener"; //$NON-NLS-1$
private static final String SET_ON_TOUCH_LISTENER_SIG = "(Landroid/view/View$OnTouchListener;)V"; //$NON-NLS-1$
private static final String ON_TOUCH = "onTouch"; //$NON-NLS-1$
private static final String ON_TOUCH_SIG = "(Landroid/view/View;Landroid/view/MotionEvent;)Z"; //$NON-NLS-1$
private static final String ON_TOUCH_LISTENER = "android/view/View$OnTouchListener"; //$NON-NLS-1$
/** Constructs a new {@link ClickableViewAccessibilityDetector} */
public ClickableViewAccessibilityDetector() {
}
@NonNull
@Override
public Speed getSpeed() {
return Speed.FAST;
}
// ---- Implements ClassScanner ----
@Override
public void checkClass(@NonNull ClassContext context, @NonNull ClassNode classNode) {
scanForAndCheckSetOnTouchListenerCalls(context, classNode);
// Ignore abstract classes.
if ((classNode.access & Opcodes.ACC_ABSTRACT) != 0) {
return;
}
if (context.getDriver().isSubclassOf(classNode, ANDROID_VIEW_VIEW)) {
checkView(context, classNode);
}
if (implementsOnTouchListener(classNode)) {
checkOnTouchListener(context, classNode);
}
}
@SuppressWarnings("unchecked") // ASM API
public static void scanForAndCheckSetOnTouchListenerCalls(
ClassContext context,
ClassNode classNode) {
List methods = classNode.methods;
for (MethodNode methodNode : methods) {
ListIterator iterator = methodNode.instructions.iterator();
while (iterator.hasNext()) {
AbstractInsnNode abstractInsnNode = iterator.next();
if (abstractInsnNode.getType() == AbstractInsnNode.METHOD_INSN) {
MethodInsnNode methodInsnNode = (MethodInsnNode) abstractInsnNode;
if (methodInsnNode.name.equals(SET_ON_TOUCH_LISTENER)
&& methodInsnNode.desc.equals(SET_ON_TOUCH_LISTENER_SIG)) {
checkSetOnTouchListenerCall(context, methodNode, methodInsnNode);
}
}
}
}
}
@SuppressWarnings("unchecked") // ASM API
public static void checkSetOnTouchListenerCall(
@NonNull ClassContext context,
@NonNull MethodNode method,
@NonNull MethodInsnNode call) {
String owner = call.owner;
// Ignore the call if it was called on a non-view.
ClassNode ownerClass = context.getDriver().findClass(context, owner, 0);
if(ownerClass == null
|| !context.getDriver().isSubclassOf(ownerClass, ANDROID_VIEW_VIEW)) {
return;
}
MethodNode performClick = findMethod(ownerClass.methods, PERFORM_CLICK, PERFORM_CLICK_SIG);
//noinspection VariableNotUsedInsideIf
if (performClick == null) {
String message = String.format(
"Custom view `%1$s` has `setOnTouchListener` called on it but does not "
+ "override `performClick`", ownerClass.name);
context.report(ISSUE, method, call, context.getLocation(call), message);
}
}
@SuppressWarnings("unchecked") // ASM API
private static void checkOnTouchListener(ClassContext context, ClassNode classNode) {
MethodNode onTouchNode =
findMethod(
classNode.methods,
ON_TOUCH,
ON_TOUCH_SIG);
if (onTouchNode != null) {
AbstractInsnNode performClickInsnNode = findMethodCallInstruction(
onTouchNode.instructions,
ANDROID_VIEW_VIEW,
PERFORM_CLICK,
PERFORM_CLICK_SIG);
if (performClickInsnNode == null) {
String message = String.format(
"`%1$s#onTouch` should call `View#performClick` when a click is detected",
classNode.name);
context.report(
ISSUE,
onTouchNode,
null,
context.getLocation(onTouchNode, classNode),
message);
}
}
}
@SuppressWarnings("unchecked") // ASM API
private static void checkView(ClassContext context, ClassNode classNode) {
MethodNode onTouchEvent = findMethod(classNode.methods, ON_TOUCH_EVENT, ON_TOUCH_EVENT_SIG);
MethodNode performClick = findMethod(classNode.methods, PERFORM_CLICK, PERFORM_CLICK_SIG);
// Check if we override onTouchEvent.
if (onTouchEvent != null) {
// Ensure that we also override performClick.
//noinspection VariableNotUsedInsideIf
if (performClick == null) {
String message = String.format(
"Custom view `%1$s` overrides `onTouchEvent` but not `performClick`",
classNode.name);
context.report(ISSUE, onTouchEvent, null,
context.getLocation(onTouchEvent, classNode), message);
} else {
// If we override performClick, ensure that it is called inside onTouchEvent.
AbstractInsnNode performClickInOnTouchEventInsnNode = findMethodCallInstruction(
onTouchEvent.instructions,
classNode.name,
PERFORM_CLICK,
PERFORM_CLICK_SIG);
if (performClickInOnTouchEventInsnNode == null) {
String message = String.format(
"`%1$s#onTouchEvent` should call `%1$s#performClick` when a click is detected",
classNode.name);
context.report(ISSUE, onTouchEvent, null,
context.getLocation(onTouchEvent, classNode), message);
}
}
}
// Ensure that, if performClick is implemented, performClick calls super.performClick.
if (performClick != null) {
AbstractInsnNode superPerformClickInPerformClickInsnNode = findMethodCallInstruction(
performClick.instructions,
classNode.superName,
PERFORM_CLICK,
PERFORM_CLICK_SIG);
if (superPerformClickInPerformClickInsnNode == null) {
String message = String.format(
"`%1$s#performClick` should call `super#performClick`",
classNode.name);
context.report(ISSUE, performClick, null,
context.getLocation(performClick, classNode), message);
}
}
}
@Nullable
private static MethodNode findMethod(
@NonNull List methods,
@NonNull String name,
@NonNull String desc) {
for (MethodNode method : methods) {
if (name.equals(method.name)
&& desc.equals(method.desc)) {
return method;
}
}
return null;
}
@SuppressWarnings("unchecked") // ASM API
@Nullable
private static AbstractInsnNode findMethodCallInstruction(
@NonNull InsnList instructions,
@NonNull String owner,
@NonNull String name,
@NonNull String desc) {
ListIterator iterator = instructions.iterator();
while (iterator.hasNext()) {
AbstractInsnNode insnNode = iterator.next();
if (insnNode.getType() == AbstractInsnNode.METHOD_INSN) {
MethodInsnNode methodInsnNode = (MethodInsnNode) insnNode;
if ((methodInsnNode.owner.equals(owner))
&& (methodInsnNode.name.equals(name))
&& (methodInsnNode.desc.equals(desc))) {
return methodInsnNode;
}
}
}
return null;
}
private static boolean implementsOnTouchListener(ClassNode classNode) {
return (classNode.interfaces != null) && (classNode.interfaces.contains(ON_TOUCH_LISTENER));
}
}
