彻底解决Android因加载多个大图引起的OutOfMemoryError，内存溢出的问题

http://blog.csdn.net/quan648997767/article/details/11560415

最近因为项目里需求是选择或者拍摄多张照片后，提供滑动预览和上传，很多照片是好几MB一张，因为目前的Android系统对运行的程序都有一定的内存限制，一般是16MB或24MB(视平台而定)，不做处理直接加载的话必然会报OOM (Out Of Memmory)。网上有很多解决android加载bitmap内存溢出的方法，我总结了一个通用的方法，下面是我从的开发案例抽取出来的代码：

我在项目中建了个Util.java工具类，里面写了个方法，根据图片的路径返回一个字节流数组对象：

 

public static byte[] decodeBitmap(String path) {
        BitmapFactory.Options opts = new BitmapFactory.Options();
        opts.inJustDecodeBounds = true;// 设置成了true,不占用内存，只获取bitmap宽高
        BitmapFactory.decodeFile(path, opts);
        opts.inSampleSize = computeSampleSize(opts, -1, 1024 * 800);
        opts.inJustDecodeBounds = false;// 这里一定要将其设置回false，因为之前我们将其设置成了true
        opts.inPurgeable = true;
        opts.inInputShareable = true;
        opts.inDither = false;
        opts.inPurgeable = true;
        opts.inTempStorage = new byte[16 * 1024];
        FileInputStream is = null;
        Bitmap bmp = null;
        ByteArrayOutputStream baos = null;
        try {
            is = new FileInputStream(path);
            bmp = BitmapFactory.decodeFileDescriptor(is.getFD(), null, opts);
            double scale = getScaling(opts.outWidth * opts.outHeight,
                    1024 * 600);
            Bitmap bmp2 = Bitmap.createScaledBitmap(bmp,
                    (int) (opts.outWidth * scale),
                    (int) (opts.outHeight * scale), true);
            bmp.recycle();
            baos = new ByteArrayOutputStream();
            bmp2.compress(Bitmap.CompressFormat.JPEG, 100, baos);
            bmp2.recycle();
            return baos.toByteArray();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                is.close();
                baos.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
            System.gc();
        }
        return baos.toByteArray();
    }

    private static double getScaling(int src, int des) {
        /**
         * 48 目标尺寸÷原尺寸 sqrt开方，得出宽高百分比 49
         */
        double scale = Math.sqrt((double) des / (double) src);
        return scale;
    }

    public static int computeSampleSize(BitmapFactory.Options options,
            int minSideLength, int maxNumOfPixels) {
        int initialSize = computeInitialSampleSize(options, minSideLength,
                maxNumOfPixels);

        int roundedSize;
        if (initialSize <= 8) {
            roundedSize = 1;
            while (roundedSize < initialSize) {
                roundedSize <<= 1;
            }
        } else {
            roundedSize = (initialSize + 7) / 8 * 8;
        }

        return roundedSize;
    }

    private static int computeInitialSampleSize(BitmapFactory.Options options,
            int minSideLength, int maxNumOfPixels) {
        double w = options.outWidth;
        double h = options.outHeight;

        int lowerBound = (maxNumOfPixels == -1) ? 1 : (int) Math.ceil(Math
                .sqrt(w * h / maxNumOfPixels));
        int upperBound = (minSideLength == -1) ? 128 : (int) Math.min(
                Math.floor(w / minSideLength), Math.floor(h / minSideLength));

        if (upperBound < lowerBound) {
            return lowerBound;
        }

        if ((maxNumOfPixels == -1) && (minSideLength == -1)) {
            return 1;
        } else if (minSideLength == -1) {
            return lowerBound;
        } else {
            return upperBound;
        }
    }

然后在我需要加载图片BitMap的地方来调用Util.decodeBitmap():

Bitmap bitmap = BitmapFactory.decodeByteArray(Util.decodeBitmap(imagePath), 0, Util.decodeBitmap(imagePath).length);
                imageCache.put(imagePath, new SoftReference<Bitmap>(bitmap));

 

上面这两行是我的AsyncImageLoaderByPath类中的代码，用来加载SD卡里面的图片，该类完整代码是：

package com.pioneer.travel.util;

import java.io.IOException;
import java.io.InputStream;
import java.lang.ref.SoftReference;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.HashMap;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.BitmapFactory.Options;
import android.graphics.drawable.Drawable;
import android.os.Handler;
import android.os.Message;
import android.provider.MediaStore;
import android.util.Log;
import android.widget.ImageView;

public class AsyncImageLoaderByPath {
    //SoftReference是软引用，是为了更好的为了系统回收变量
    private HashMap<String, SoftReference<Bitmap>> imageCache;
    private Context context;

    public AsyncImageLoaderByPath(Context context) {
        this.imageCache = new HashMap<String, SoftReference<Bitmap>>();
        this.context = context;
    }
    public Bitmap loadBitmapByPath(final String imagePath, final ImageView imageView, final ImageCallback imageCallback){
        if (imageCache.containsKey(imagePath)) {
            //从缓存中获取
            SoftReference<Bitmap> softReference = imageCache.get(imagePath);
            Bitmap bitmap = softReference.get();
            if (bitmap != null) {
                return bitmap;
            }
        }
        final Handler handler = new Handler() {
            public void handleMessage(Message message) {
                imageCallback.imageLoaded((Bitmap) message.obj, imageView, imagePath);
            }
        };
        //建立新一个获取SD卡的图片
        new Thread() {
            @Override
            public void run() {
                Bitmap bitmap = BitmapFactory.decodeByteArray(Util.decodeBitmap(imagePath), 0, Util.decodeBitmap(imagePath).length);
                imageCache.put(imagePath, new SoftReference<Bitmap>(bitmap));
                Message message = handler.obtainMessage(0, bitmap);
                handler.sendMessage(message);
            }
        }.start();
        return null;
    }
    //回调接口
    public interface ImageCallback {
        public void imageLoaded(Bitmap imageBitmap,ImageView imageView, String imagePath);
    }
}

通过这个实例，我验证了一下，一次性获取20张5MB的照片，都可以加载的很流畅，完全没有再出现报OOM的错误了

以下是运行效果

SD卡中的图片：