1 /* 2 * Copyright (C) 2011 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package com.example.android.supportv4.accessibility; 18 19 import android.app.Activity; 20 import android.content.Context; 21 import android.os.Bundle; 22 import android.support.v4.view.AccessibilityDelegateCompat; 23 import android.support.v4.view.ViewCompat; 24 import android.support.v4.view.accessibility.AccessibilityNodeInfoCompat; 25 import android.util.AttributeSet; 26 import android.view.View; 27 import android.view.accessibility.AccessibilityEvent; 28 29 import com.example.android.supportv4.R; 30 31 /** 32 * This class demonstrates how to use the support library to register 33 * a View.AccessibilityDelegate that customizes the accessibility 34 * behavior of a View. Aiming to maximize simplicity this example 35 * tweaks the text reported to accessibility services but using 36 * these APIs a client can inject any accessibility functionality into 37 * a View. 38 */ 39 public class AccessibilityDelegateSupportActivity extends Activity { 40 41 /** 42 * {@inheritDoc} 43 */ 44 @Override 45 public void onCreate(Bundle savedInstanceState) { 46 super.onCreate(savedInstanceState); 47 setContentView(R.layout.accessibility_delegate); 48 } 49 50 /** 51 * This class represents a View that is customized via an AccessibilityDelegate 52 * as opposed to inheritance. An accessibility delegate can be used for adding 53 * accessibility to custom Views, i.e. ones that extend classes from android.view, 54 * in a backwards compatible fashion. Note that overriding a method whose return 55 * type or arguments are not part of a target platform APIs makes your application 56 * not backwards compatible with that platform version. 57 */ 58 public static class AccessibilityDelegateSupportView extends View { 59 60 public AccessibilityDelegateSupportView(Context context, AttributeSet attrs) { 61 super(context, attrs); 62 installAccessibilityDelegate(); 63 } 64 65 private void installAccessibilityDelegate() { 66 // The accessibility delegate enables customizing accessibility behavior 67 // via composition as opposed as inheritance. The main benefit is that 68 // one can write a backwards compatible application by setting the delegate 69 // only if the API level is high enough i.e. the delegate is part of the APIs. 70 // The easiest way to achieve that is by using the support library which 71 // takes the burden of checking API version and knowing which API version 72 // introduced the delegate off the developer. 73 ViewCompat.setAccessibilityDelegate(this, new AccessibilityDelegateCompat() { 74 @Override 75 public void onPopulateAccessibilityEvent(View host, AccessibilityEvent event) { 76 super.onPopulateAccessibilityEvent(host, event); 77 // Note that View.onPopulateAccessibilityEvent was introduced in 78 // ICS and we would like to tweak a bit the text that is reported to 79 // accessibility services via the AccessibilityEvent. 80 event.getText().add(getContext().getString( 81 R.string.accessibility_delegate_custom_text_added)); 82 } 83 84 @Override 85 public void onInitializeAccessibilityNodeInfo(View host, 86 AccessibilityNodeInfoCompat info) { 87 super.onInitializeAccessibilityNodeInfo(host, info); 88 // Note that View.onInitializeAccessibilityNodeInfo was introduced in 89 // ICS and we would like to tweak a bit the text that is reported to 90 // accessibility services via the AccessibilityNodeInfo. 91 info.setText(getContext().getString( 92 R.string.accessibility_delegate_custom_text_added)); 93 } 94 }); 95 } 96 } 97 } 98
