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      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 
     17 package android.widget;
     18 
     19 import android.content.Context;
     20 import android.util.AttributeSet;
     21 import android.view.accessibility.AccessibilityEvent;
     22 import android.view.accessibility.AccessibilityNodeInfo;
     23 import 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
     72 public 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