1 /*
2  * Copyright (C) 2009 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.apis.graphics;
18 
19 import android.content.Context;
20 import android.graphics.Bitmap;
21 import android.graphics.BitmapFactory;
22 import android.graphics.Canvas;
23 import android.graphics.Color;
24 import android.graphics.Paint;
25 import android.graphics.BitmapFactory.Options;
26 import android.view.View;
27 
28 import java.io.ByteArrayOutputStream;
29 
30 /**
31  * PurgeableBitmapView works with PurgeableBitmap to demonstrate the effects of setting
32  * Bitmaps as being purgeable.
33  *
34  * PurgeableBitmapView decodes an encoded bitstream to a Bitmap each time update()
35  * is invoked(), and its onDraw() draws the Bitmap and a number to screen.
36  * The number is used to indicate the number of Bitmaps that has been decoded.
37  */
38 public class PurgeableBitmapView extends View {
39     private final byte[] bitstream;
40 
41     private Bitmap mBitmap;
42     private final int mArraySize = 200;
43     private final Bitmap[] mBitmapArray = new Bitmap [mArraySize];
44     private final Options mOptions = new Options();
45     private static final int WIDTH = 150;
46     private static final int HEIGHT = 450;
47     private static final int STRIDE = 320;   // must be >= WIDTH
48     private int mDecodingCount = 0;
49     private final Paint mPaint = new Paint();
50     private final int textSize = 32;
51     private static int delay = 100;
52 
PurgeableBitmapView(Context context, boolean isPurgeable)53     public PurgeableBitmapView(Context context, boolean isPurgeable) {
54         super(context);
55         setFocusable(true);
56         mOptions.inPurgeable = isPurgeable;
57 
58         int[] colors = createColors();
59         Bitmap src = Bitmap.createBitmap(colors, 0, STRIDE, WIDTH, HEIGHT,
60                 Bitmap.Config.ARGB_8888);
61         bitstream = generateBitstream(src, Bitmap.CompressFormat.JPEG, 80);
62 
63         mPaint.setTextSize(textSize);
64         mPaint.setColor(Color.GRAY);
65     }
66 
createColors()67     private int[] createColors() {
68         int[] colors = new int[STRIDE * HEIGHT];
69         for (int y = 0; y < HEIGHT; y++) {
70             for (int x = 0; x < WIDTH; x++) {
71                 int r = x * 255 / (WIDTH - 1);
72                 int g = y * 255 / (HEIGHT - 1);
73                 int b = 255 - Math.min(r, g);
74                 int a = Math.max(r, g);
75                 colors[y * STRIDE + x] = (a << 24) | (r << 16) | (g << 8) | b;
76             }
77         }
78         return colors;
79     }
80 
update(PurgeableBitmap.RefreshHandler handler)81     public int update(PurgeableBitmap.RefreshHandler handler) {
82         try {
83             mBitmapArray[mDecodingCount] = BitmapFactory.decodeByteArray(
84                 bitstream, 0, bitstream.length, mOptions);
85             mBitmap = mBitmapArray[mDecodingCount];
86             mDecodingCount++;
87             if (mDecodingCount < mArraySize) {
88                 handler.sleep(delay);
89                 return 0;
90             } else {
91                 return -mDecodingCount;
92             }
93 
94         } catch (OutOfMemoryError error) {
95             for (int i = 0; i < mDecodingCount; i++) {
96                 mBitmapArray[i].recycle();
97             }
98             return mDecodingCount + 1;
99         }
100     }
101 
onDraw(Canvas canvas)102     @Override protected void onDraw(Canvas canvas) {
103         canvas.drawColor(Color.WHITE);
104         canvas.drawBitmap(mBitmap, 0, 0, null);
105         canvas.drawText(String.valueOf(mDecodingCount), WIDTH / 2 - 20,
106             HEIGHT / 2, mPaint);
107     }
108 
generateBitstream(Bitmap src, Bitmap.CompressFormat format, int quality)109     private byte[] generateBitstream(Bitmap src, Bitmap.CompressFormat format,
110             int quality) {
111         ByteArrayOutputStream os = new ByteArrayOutputStream();
112         src.compress(format, quality, os);
113         return os.toByteArray();
114     }
115 
116 }
117