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