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      1 /*
      2  * Copyright (C) 2006 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 
     24 import com.android.internal.R;
     25 
     26 
     27 /**
     28  * <p>
     29  * A radio button is a two-states button that can be either checked or
     30  * unchecked. When the radio button is unchecked, the user can press or click it
     31  * to check it. However, contrary to a {@link android.widget.CheckBox}, a radio
     32  * button cannot be unchecked by the user once checked.
     33  * </p>
     34  *
     35  * <p>
     36  * Radio buttons are normally used together in a
     37  * {@link android.widget.RadioGroup}. When several radio buttons live inside
     38  * a radio group, checking one radio button unchecks all the others.</p>
     39  * </p>
     40  *
     41  * <p>See the <a href="{@docRoot}guide/topics/ui/controls/radiobutton.html">Radio Buttons</a>
     42  * guide.</p>
     43  *
     44  * <p><strong>XML attributes</strong></p>
     45  * <p>
     46  * See {@link android.R.styleable#CompoundButton CompoundButton Attributes},
     47  * {@link android.R.styleable#Button Button Attributes},
     48  * {@link android.R.styleable#TextView TextView Attributes},
     49  * {@link android.R.styleable#View View Attributes}
     50  * </p>
     51  */
     52 public class RadioButton extends CompoundButton {
     53 
     54     public RadioButton(Context context) {
     55         this(context, null);
     56     }
     57 
     58     public RadioButton(Context context, AttributeSet attrs) {
     59         this(context, attrs, com.android.internal.R.attr.radioButtonStyle);
     60     }
     61 
     62     public RadioButton(Context context, AttributeSet attrs, int defStyle) {
     63         super(context, attrs, defStyle);
     64     }
     65 
     66     /**
     67      * {@inheritDoc}
     68      * <p>
     69      * If the radio button is already checked, this method will not toggle the radio button.
     70      */
     71     @Override
     72     public void toggle() {
     73         // we override to prevent toggle when the radio is already
     74         // checked (as opposed to check boxes widgets)
     75         if (!isChecked()) {
     76             super.toggle();
     77         }
     78     }
     79 
     80     @Override
     81     public void onInitializeAccessibilityEvent(AccessibilityEvent event) {
     82         super.onInitializeAccessibilityEvent(event);
     83         event.setClassName(RadioButton.class.getName());
     84     }
     85 
     86     @Override
     87     public void onInitializeAccessibilityNodeInfo(AccessibilityNodeInfo info) {
     88         super.onInitializeAccessibilityNodeInfo(info);
     89         info.setClassName(RadioButton.class.getName());
     90     }
     91 }
     92