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      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 
     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 
     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 
     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 
    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 
    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