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/*
* 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.supportv4.accessibility;
import android.app.Activity;
import android.content.Context;
import android.os.Bundle;
import android.support.v4.view.AccessibilityDelegateCompat;
import android.support.v4.view.ViewCompat;
import android.support.v4.view.accessibility.AccessibilityNodeInfoCompat;
import android.util.AttributeSet;
import android.view.View;
import android.view.accessibility.AccessibilityEvent;
import com.example.android.supportv4.R;
/**
* This class demonstrates how to use the support library to register
* a View.AccessibilityDelegate that customizes the accessibility
* behavior of a View. Aiming to maximize simplicity this example
* tweaks the text reported to accessibility services but using
* these APIs a client can inject any accessibility functionality into
* a View.
*/
public class AccessibilityDelegateSupportActivity extends Activity {
/**
* {@inheritDoc}
*/
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.accessibility_delegate);
}
/**
* This class represents a View that is customized via an AccessibilityDelegate
* as opposed to inheritance. An accessibility delegate can be used for adding
* accessibility to custom Views, i.e. ones that extend classes from android.view,
* in a backwards compatible fashion. Note that overriding a method whose return
* type or arguments are not part of a target platform APIs makes your application
* not backwards compatible with that platform version.
*/
public static class AccessibilityDelegateSupportView extends View {
public AccessibilityDelegateSupportView(Context context, AttributeSet attrs) {
super(context, attrs);
installAccessibilityDelegate();
}
private void installAccessibilityDelegate() {
// The accessibility delegate enables customizing accessibility behavior
// via composition as opposed as inheritance. The main benefit is that
// one can write a backwards compatible application by setting the delegate
// only if the API level is high enough i.e. the delegate is part of the APIs.
// The easiest way to achieve that is by using the support library which
// takes the burden of checking API version and knowing which API version
// introduced the delegate off the developer.
ViewCompat.setAccessibilityDelegate(this, new AccessibilityDelegateCompat() {
@Override
public void onPopulateAccessibilityEvent(View host, AccessibilityEvent event) {
super.onPopulateAccessibilityEvent(host, event);
// Note that View.onPopulateAccessibilityEvent was introduced in
// ICS and we would like to tweak a bit the text that is reported to
// accessibility services via the AccessibilityEvent.
event.getText().add(getContext().getString(
R.string.accessibility_delegate_custom_text_added));
}
@Override
public void onInitializeAccessibilityNodeInfo(View host,
AccessibilityNodeInfoCompat info) {
super.onInitializeAccessibilityNodeInfo(host, info);
// Note that View.onInitializeAccessibilityNodeInfo was introduced in
// ICS and we would like to tweak a bit the text that is reported to
// accessibility services via the AccessibilityNodeInfo.
info.setText(getContext().getString(
R.string.accessibility_delegate_custom_text_added));
}
});
}
}
}
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