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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.os.Handler;
     21 import android.os.Message;
     22 import android.util.AttributeSet;
     23 import android.view.MotionEvent;
     24 import android.view.accessibility.AccessibilityEvent;
     25 import android.view.accessibility.AccessibilityNodeInfo;
     26 import android.widget.RemoteViews.RemoteView;
     27 
     28 import java.util.Map;
     29 
     30 /**
     31  * <p>
     32  * Displays a button with an image (instead of text) that can be pressed
     33  * or clicked by the user. By default, an ImageButton looks like a regular
     34  * {@link android.widget.Button}, with the standard button background
     35  * that changes color during different button states. The image on the surface
     36  * of the button is defined either by the {@code android:src} attribute in the
     37  * {@code <ImageButton>} XML element or by the
     38  * {@link #setImageResource(int)} method.</p>
     39  *
     40  * <p>To remove the standard button background image, define your own
     41  * background image or set the background color to be transparent.</p>
     42  * <p>To indicate the different button states (focused, selected, etc.), you can
     43  * define a different image for each state. E.g., a blue image by default, an
     44  * orange one for when focused, and a yellow one for when pressed. An easy way to
     45  * do this is with an XML drawable "selector." For example:</p>
     46  * <pre>
     47  * &lt;?xml version="1.0" encoding="utf-8"?&gt;
     48  * &lt;selector xmlns:android="http://schemas.android.com/apk/res/android"&gt;
     49  *     &lt;item android:state_pressed="true"
     50  *           android:drawable="@drawable/button_pressed" /&gt; &lt;!-- pressed --&gt;
     51  *     &lt;item android:state_focused="true"
     52  *           android:drawable="@drawable/button_focused" /&gt; &lt;!-- focused --&gt;
     53  *     &lt;item android:drawable="@drawable/button_normal" /&gt; &lt;!-- default --&gt;
     54  * &lt;/selector&gt;</pre>
     55  *
     56  * <p>Save the XML file in your project {@code res/drawable/} folder and then
     57  * reference it as a drawable for the source of your ImageButton (in the
     58  * {@code android:src} attribute). Android will automatically change the image
     59  * based on the state of the button and the corresponding images
     60  * defined in the XML.</p>
     61  *
     62  * <p>The order of the {@code <item>} elements is important because they are
     63  * evaluated in order. This is why the "normal" button image comes last, because
     64  * it will only be applied after {@code android:state_pressed} and {@code
     65  * android:state_focused} have both evaluated false.</p>
     66  *
     67  * <p>See the <a href="{@docRoot}guide/topics/ui/controls/button.html">Buttons</a>
     68  * guide.</p>
     69  *
     70  * <p><strong>XML attributes</strong></p>
     71  * <p>
     72  * See {@link android.R.styleable#ImageView Button Attributes},
     73  * {@link android.R.styleable#View View Attributes}
     74  * </p>
     75  */
     76 @RemoteView
     77 public class ImageButton extends ImageView {
     78     public ImageButton(Context context) {
     79         this(context, null);
     80     }
     81 
     82     public ImageButton(Context context, AttributeSet attrs) {
     83         this(context, attrs, com.android.internal.R.attr.imageButtonStyle);
     84     }
     85 
     86     public ImageButton(Context context, AttributeSet attrs, int defStyle) {
     87         super(context, attrs, defStyle);
     88         setFocusable(true);
     89     }
     90 
     91     @Override
     92     protected boolean onSetAlpha(int alpha) {
     93         return false;
     94     }
     95 
     96     @Override
     97     public void onInitializeAccessibilityEvent(AccessibilityEvent event) {
     98         super.onInitializeAccessibilityEvent(event);
     99         event.setClassName(ImageButton.class.getName());
    100     }
    101 
    102     @Override
    103     public void onInitializeAccessibilityNodeInfo(AccessibilityNodeInfo info) {
    104         super.onInitializeAccessibilityNodeInfo(info);
    105         info.setClassName(ImageButton.class.getName());
    106     }
    107 }
    108