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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.View;
     22 import android.view.ViewGroup;
     23 import android.view.accessibility.AccessibilityEvent;
     24 import android.view.accessibility.AccessibilityNodeInfo;
     25 
     26 /**
     27  * {@link ViewAnimator} that switches between two views, and has a factory
     28  * from which these views are created.  You can either use the factory to
     29  * create the views, or add them yourself.  A ViewSwitcher can only have two
     30  * child views, of which only one is shown at a time.
     31  */
     32 public class ViewSwitcher extends ViewAnimator {
     33     /**
     34      * The factory used to create the two children.
     35      */
     36     ViewFactory mFactory;
     37 
     38     /**
     39      * Creates a new empty ViewSwitcher.
     40      *
     41      * @param context the application's environment
     42      */
     43     public ViewSwitcher(Context context) {
     44         super(context);
     45     }
     46 
     47     /**
     48      * Creates a new empty ViewSwitcher for the given context and with the
     49      * specified set attributes.
     50      *
     51      * @param context the application environment
     52      * @param attrs a collection of attributes
     53      */
     54     public ViewSwitcher(Context context, AttributeSet attrs) {
     55         super(context, attrs);
     56     }
     57 
     58     /**
     59      * {@inheritDoc}
     60      *
     61      * @throws IllegalStateException if this switcher already contains two children
     62      */
     63     @Override
     64     public void addView(View child, int index, ViewGroup.LayoutParams params) {
     65         if (getChildCount() >= 2) {
     66             throw new IllegalStateException("Can't add more than 2 views to a ViewSwitcher");
     67         }
     68         super.addView(child, index, params);
     69     }
     70 
     71     @Override
     72     public void onInitializeAccessibilityEvent(AccessibilityEvent event) {
     73         super.onInitializeAccessibilityEvent(event);
     74         event.setClassName(ViewSwitcher.class.getName());
     75     }
     76 
     77     @Override
     78     public void onInitializeAccessibilityNodeInfo(AccessibilityNodeInfo info) {
     79         super.onInitializeAccessibilityNodeInfo(info);
     80         info.setClassName(ViewSwitcher.class.getName());
     81     }
     82 
     83     /**
     84      * Returns the next view to be displayed.
     85      *
     86      * @return the view that will be displayed after the next views flip.
     87      */
     88     public View getNextView() {
     89         int which = mWhichChild == 0 ? 1 : 0;
     90         return getChildAt(which);
     91     }
     92 
     93     private View obtainView() {
     94         View child = mFactory.makeView();
     95         LayoutParams lp = (LayoutParams) child.getLayoutParams();
     96         if (lp == null) {
     97             lp = new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT);
     98         }
     99         addView(child, lp);
    100         return child;
    101     }
    102 
    103     /**
    104      * Sets the factory used to create the two views between which the
    105      * ViewSwitcher will flip. Instead of using a factory, you can call
    106      * {@link #addView(android.view.View, int, android.view.ViewGroup.LayoutParams)}
    107      * twice.
    108      *
    109      * @param factory the view factory used to generate the switcher's content
    110      */
    111     public void setFactory(ViewFactory factory) {
    112         mFactory = factory;
    113         obtainView();
    114         obtainView();
    115     }
    116 
    117     /**
    118      * Reset the ViewSwitcher to hide all of the existing views and to make it
    119      * think that the first time animation has not yet played.
    120      */
    121     public void reset() {
    122         mFirstTime = true;
    123         View v;
    124         v = getChildAt(0);
    125         if (v != null) {
    126             v.setVisibility(View.GONE);
    127         }
    128         v = getChildAt(1);
    129         if (v != null) {
    130             v.setVisibility(View.GONE);
    131         }
    132     }
    133 
    134     /**
    135      * Creates views in a ViewSwitcher.
    136      */
    137     public interface ViewFactory {
    138         /**
    139          * Creates a new {@link android.view.View} to be added in a
    140          * {@link android.widget.ViewSwitcher}.
    141          *
    142          * @return a {@link android.view.View}
    143          */
    144         View makeView();
    145     }
    146 }
    147 
    148