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
17package com.example.android.supportv4.accessibility;
18
19import android.app.Activity;
20import android.content.Context;
21import android.os.Bundle;
22import android.support.v4.view.AccessibilityDelegateCompat;
23import android.support.v4.view.ViewCompat;
24import android.support.v4.view.accessibility.AccessibilityNodeInfoCompat;
25import android.util.AttributeSet;
26import android.view.View;
27import android.view.accessibility.AccessibilityEvent;
28
29import 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 */
39public 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