1/*
2 * Copyright (C) 2007 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 android.widget;
18
19import android.content.Context;
20import android.util.AttributeSet;
21import android.view.accessibility.AccessibilityEvent;
22import android.view.accessibility.AccessibilityNodeInfo;
23import android.widget.RemoteViews.RemoteView;
24
25/**
26 * <p>
27 * Displays a button with an image (instead of text) that can be pressed
28 * or clicked by the user. By default, an ImageButton looks like a regular
29 * {@link android.widget.Button}, with the standard button background
30 * that changes color during different button states. The image on the surface
31 * of the button is defined either by the {@code android:src} attribute in the
32 * {@code <ImageButton>} XML element or by the
33 * {@link #setImageResource(int)} method.</p>
34 *
35 * <p>To remove the standard button background image, define your own
36 * background image or set the background color to be transparent.</p>
37 * <p>To indicate the different button states (focused, selected, etc.), you can
38 * define a different image for each state. E.g., a blue image by default, an
39 * orange one for when focused, and a yellow one for when pressed. An easy way to
40 * do this is with an XML drawable "selector." For example:</p>
41 * <pre>
42 * &lt;?xml version="1.0" encoding="utf-8"?&gt;
43 * &lt;selector xmlns:android="http://schemas.android.com/apk/res/android"&gt;
44 *     &lt;item android:state_pressed="true"
45 *           android:drawable="@drawable/button_pressed" /&gt; &lt;!-- pressed --&gt;
46 *     &lt;item android:state_focused="true"
47 *           android:drawable="@drawable/button_focused" /&gt; &lt;!-- focused --&gt;
48 *     &lt;item android:drawable="@drawable/button_normal" /&gt; &lt;!-- default --&gt;
49 * &lt;/selector&gt;</pre>
50 *
51 * <p>Save the XML file in your project {@code res/drawable/} folder and then
52 * reference it as a drawable for the source of your ImageButton (in the
53 * {@code android:src} attribute). Android will automatically change the image
54 * based on the state of the button and the corresponding images
55 * defined in the XML.</p>
56 *
57 * <p>The order of the {@code <item>} elements is important because they are
58 * evaluated in order. This is why the "normal" button image comes last, because
59 * it will only be applied after {@code android:state_pressed} and {@code
60 * android:state_focused} have both evaluated false.</p>
61 *
62 * <p>See the <a href="{@docRoot}guide/topics/ui/controls/button.html">Buttons</a>
63 * guide.</p>
64 *
65 * <p><strong>XML attributes</strong></p>
66 * <p>
67 * See {@link android.R.styleable#ImageView Button Attributes},
68 * {@link android.R.styleable#View View Attributes}
69 * </p>
70 */
71@RemoteView
72public class ImageButton extends ImageView {
73    public ImageButton(Context context) {
74        this(context, null);
75    }
76
77    public ImageButton(Context context, AttributeSet attrs) {
78        this(context, attrs, com.android.internal.R.attr.imageButtonStyle);
79    }
80
81    public ImageButton(Context context, AttributeSet attrs, int defStyleAttr) {
82        this(context, attrs, defStyleAttr, 0);
83    }
84
85    public ImageButton(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
86        super(context, attrs, defStyleAttr, defStyleRes);
87        setFocusable(true);
88    }
89
90    @Override
91    protected boolean onSetAlpha(int alpha) {
92        return false;
93    }
94
95    @Override
96    public void onInitializeAccessibilityEvent(AccessibilityEvent event) {
97        super.onInitializeAccessibilityEvent(event);
98        event.setClassName(ImageButton.class.getName());
99    }
100
101    @Override
102    public void onInitializeAccessibilityNodeInfo(AccessibilityNodeInfo info) {
103        super.onInitializeAccessibilityNodeInfo(info);
104        info.setClassName(ImageButton.class.getName());
105    }
106}
107