The file containing the source code shown below is located in the corresponding directory in <sdk>/samples/android-<version>/...
/*
* 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.example.android.apis.accessibility;
import com.example.android.apis.R;
import android.accessibilityservice.AccessibilityService;
import android.text.TextUtils;
import android.util.Log;
import android.view.accessibility.AccessibilityEvent;
import android.view.accessibility.AccessibilityNodeInfo;
import android.view.accessibility.AccessibilityRecord;
import android.speech.tts.TextToSpeech;
import android.speech.tts.TextToSpeech.OnInitListener;
import java.util.Locale;
/**
* This class demonstrates how an accessibility service can query
* window content to improve the feedback given to the user.
*/
public class TaskBackService extends AccessibilityService implements OnInitListener {
/** Tag for logging. */
private static final String LOG_TAG = "TaskBackService/onAccessibilityEvent";
/** Comma separator. */
private static final String SEPARATOR = ", ";
/** The class name of TaskListView - for simplicity we speak only its items. */
private static final String TASK_LIST_VIEW_CLASS_NAME =
"com.example.android.apis.accessibility.TaskListView";
/** Flag whether Text-To-Speech is initialized. */
private boolean mTextToSpeechInitialized;
/** Handle to the Text-To-Speech engine. */
private TextToSpeech mTts;
/**
* {@inheritDoc}
*/
@Override
public void onServiceConnected() {
// Initializes the Text-To-Speech engine as soon as the service is connected.
mTts = new TextToSpeech(getApplicationContext(), this);
}
/**
* Processes an AccessibilityEvent, by traversing the View's tree and
* putting together a message to speak to the user.
*/
@Override
public void onAccessibilityEvent(AccessibilityEvent event) {
if (!mTextToSpeechInitialized) {
Log.e(LOG_TAG, "Text-To-Speech engine not ready. Bailing out.");
return;
}
// This AccessibilityNodeInfo represents the view that fired the
// AccessibilityEvent. The following code will use it to traverse the
// view hierarchy, using this node as a starting point.
//
// NOTE: Every method that returns an AccessibilityNodeInfo may return null,
// because the explored window is in another process and the
// corresponding View might be gone by the time your request reaches the
// view hierarchy.
AccessibilityNodeInfo source = event.getSource();
if (source == null) {
return;
}
// Grab the parent of the view that fired the event.
AccessibilityNodeInfo rowNode = getListItemNodeInfo(source);
if (rowNode == null) {
return;
}
// Using this parent, get references to both child nodes, the label and the checkbox.
AccessibilityNodeInfo labelNode = rowNode.getChild(0);
if (labelNode == null) {
rowNode.recycle();
return;
}
AccessibilityNodeInfo completeNode = rowNode.getChild(1);
if (completeNode == null) {
rowNode.recycle();
return;
}
// Determine what the task is and whether or not it's complete, based on
// the text inside the label, and the state of the check-box.
if (rowNode.getChildCount() < 2 || !rowNode.getChild(1).isCheckable()) {
rowNode.recycle();
return;
}
CharSequence taskLabel = labelNode.getText();
final boolean isComplete = completeNode.isChecked();
String completeStr = null;
if (isComplete) {
completeStr = getString(R.string.task_complete);
} else {
completeStr = getString(R.string.task_not_complete);
}
String taskStr = getString(R.string.task_complete_template, taskLabel, completeStr);
StringBuilder utterance = new StringBuilder(taskStr);
// The custom ListView added extra context to the event by adding an
// AccessibilityRecord to it. Extract that from the event and read it.
final int records = event.getRecordCount();
for (int i = 0; i < records; i++) {
AccessibilityRecord record = event.getRecord(i);
CharSequence contentDescription = record.getContentDescription();
if (!TextUtils.isEmpty(contentDescription )) {
utterance.append(SEPARATOR);
utterance.append(contentDescription);
}
}
// Announce the utterance.
mTts.speak(utterance.toString(), TextToSpeech.QUEUE_FLUSH, null);
Log.d(LOG_TAG, utterance.toString());
}
private AccessibilityNodeInfo getListItemNodeInfo(AccessibilityNodeInfo source) {
AccessibilityNodeInfo current = source;
while (true) {
AccessibilityNodeInfo parent = current.getParent();
if (parent == null) {
return null;
}
if (TASK_LIST_VIEW_CLASS_NAME.equals(parent.getClassName())) {
return current;
}
// NOTE: Recycle the infos.
AccessibilityNodeInfo oldCurrent = current;
current = parent;
oldCurrent.recycle();
}
}
/**
* {@inheritDoc}
*/
@Override
public void onInterrupt() {
/* do nothing */
}
/**
* {@inheritDoc}
*/
@Override
public void onInit(int status) {
// Set a flag so that the TaskBackService knows that the Text-To-Speech
// engine has been initialized, and can now handle speaking requests.
if (status == TextToSpeech.SUCCESS) {
mTts.setLanguage(Locale.US);
mTextToSpeechInitialized = true;
}
}
/**
* {@inheritDoc}
*/
@Override
public void onDestroy() {
super.onDestroy();
if (mTextToSpeechInitialized) {
mTts.shutdown();
}
}
}