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【转】解决Android因加载多个大图引起的OutOfMemoryError，内存溢出的问题
本文来自：http://blog.csdn.net/wulianghuan/article/details/11548373，感谢原作者的分享。
目标是读取SD卡中的图片并且展示出来
主要思路是通过一个工具类来压缩来自sd卡中的图片，最后通过缓存机制来避免占用过多内存。
Util.java
package com.kale.socketactivity;import java.io.ByteArrayOutputStream;import java.io.FileInputStream;import java.io.FileNotFoundException;import java.io.IOException;import android.graphics.Bitmap;import android.graphics.BitmapFactory;public class Util { /** * @param path * @return * @example Bitmap bitmap = BitmapFactory.decodeByteArray(Util.decodeBitmap(imagePath), 0, Util.decodeBitmap(imagePath).length); imageCache.put(imagePath, new SoftReference<Bitmap>(bitmap)); //这里用了软引用 */ 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); //从文件中读取图片，可以换为别的方式 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; } }}
使用方式：
Bitmap bitmap = BitmapFactory.decodeByteArray(Util.decodeBitmap(imagePath), 0, Util.decodeBitmap(imagePath).length); imageCache.put(imagePath, new SoftReference<Bitmap>(bitmap));
实现类
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); }}
【转】解决Android因加载多个大图引起的OutOfMemoryError，内存溢出的问题
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