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));
    

 

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
    
     > imageCache;    private Context context;        public AsyncImageLoaderByPath(Context context) {        this.imageCache = new HashMap
     
      >();        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
      
        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));                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：

进入应用，选择11张照片进行滑动预览：

希望以上所写对大家有帮助，谢谢！