Show navigation Hide navigation
DisplayingBitmaps / src / com.example.android.displayingbitmaps / ui /

RecyclingImageView.java

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
}