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      1 /*
      2  * Copyright (C) 2013 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 com.example.android.displayingbitmaps.ui;
     18 
     19 import android.content.Context;
     20 import android.graphics.drawable.Drawable;
     21 import android.graphics.drawable.LayerDrawable;
     22 import android.util.AttributeSet;
     23 import android.widget.ImageView;
     24 
     25 import com.example.android.displayingbitmaps.util.RecyclingBitmapDrawable;
     26 
     27 /**
     28  * Sub-class of ImageView which automatically notifies the drawable when it is
     29  * being displayed.
     30  */
     31 public class RecyclingImageView extends ImageView {
     32 
     33     public RecyclingImageView(Context context) {
     34         super(context);
     35     }
     36 
     37     public RecyclingImageView(Context context, AttributeSet attrs) {
     38         super(context, attrs);
     39     }
     40 
     41     /**
     42      * @see android.widget.ImageView#onDetachedFromWindow()
     43      */
     44     @Override
     45     protected void onDetachedFromWindow() {
     46         // This has been detached from Window, so clear the drawable
     47         setImageDrawable(null);
     48 
     49         super.onDetachedFromWindow();
     50     }
     51 
     52     /**
     53      * @see android.widget.ImageView#setImageDrawable(android.graphics.drawable.Drawable)
     54      */
     55     @Override
     56     public void setImageDrawable(Drawable drawable) {
     57         // Keep hold of previous Drawable
     58         final Drawable previousDrawable = getDrawable();
     59 
     60         // Call super to set new Drawable
     61         super.setImageDrawable(drawable);
     62 
     63         // Notify new Drawable that it is being displayed
     64         notifyDrawable(drawable, true);
     65 
     66         // Notify old Drawable so it is no longer being displayed
     67         notifyDrawable(previousDrawable, false);
     68     }
     69 
     70     /**
     71      * Notifies the drawable that it's displayed state has changed.
     72      *
     73      * @param drawable
     74      * @param isDisplayed
     75      */
     76     private static void notifyDrawable(Drawable drawable, final boolean isDisplayed) {
     77         if (drawable instanceof RecyclingBitmapDrawable) {
     78             // The drawable is a CountingBitmapDrawable, so notify it
     79             ((RecyclingBitmapDrawable) drawable).setIsDisplayed(isDisplayed);
     80         } else if (drawable instanceof LayerDrawable) {
     81             // The drawable is a LayerDrawable, so recurse on each layer
     82             LayerDrawable layerDrawable = (LayerDrawable) drawable;
     83             for (int i = 0, z = layerDrawable.getNumberOfLayers(); i < z; i++) {
     84                 notifyDrawable(layerDrawable.getDrawable(i), isDisplayed);
     85             }
     86         }
     87     }
     88 
     89 }
     90