android异步加载图片

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# import java.io.FilterInputStream; # import java.io.IOException; # import java.io.InputStream; # import java.lang.ref.SoftReference; # import java.util.HashMap; # # # import android.graphics.Bitmap; # import android.graphics.BitmapFactory; # import android.os.Handler; # import android.os.Message; # /** # * @Author Tal # * @Time 2011-3-16上午11:27:16 # * @Email dangzhengtao@gamil.com # * @Type 异步加载图片 # */ # public class AsyncImageLoader { # /** # * SoftReference是软引用，是为了更好的为了系统回收变量，重复的URL直接返回已有的资源，实现回调函数，让数据成功后，更新到UI线程。 # * 在Java中内存管理，引用分为四大类，强引用HardReference、弱引用WeakReference、软引用SoftReference和虚引用PhantomReference。 # * 它们的区别也很明显，HardReference对象是即使虚拟机内存吃紧抛出OOM也不会导致这一引用的对象被回收， # * 而WeakReference等更适合于一些数量不多，但体积稍微庞大的对象，在这四个引用中，它是最容易被垃圾回收的， # * 而我们对于显示类似Android Market中每个应用的App Icon时可以考虑使用SoftReference来解决内存不至于快速回收， # * 同时当内存短缺面临Java VM崩溃抛出OOM前时，软引用将会强制回收内存，最后的虚引用一般没有实际意义， # * 仅仅观察GC的活动状态，对于测试比较实用同时必须和ReferenceQueue一起使用。 # */ # private HashMap> imageCache = null; # # public AsyncImageLoader() { # imageCache = new HashMap>(); # } # # public Bitmap loadBitmap(final String imageUrl, final ImageCallback imageCallback) { # if (imageCache.containsKey(imageUrl)) { # SoftReference softReference = imageCache.get(imageUrl); # Bitmap Bitmap = softReference.get(); # if (Bitmap != null) { # return Bitmap; # } # } # final Handler handler = new Handler() { # public void handleMessage(Message message) { # imageCallback.imageLoaded((Bitmap) message.obj, imageUrl); # } # }; # new Thread() { # @Override # public void run() { # Bitmap bitmap = loadImageFromUrl(imageUrl); # if(bitmap!=null){ # imageCache.put(imageUrl, new SoftReference(bitmap)); # Message message = handler.obtainMessage(0, bitmap); # handler.sendMessage(message); # } # # # } # }.start(); # return null; # } # # public static Bitmap loadImageFromUrl(String path) { # try { # InputStream is = NetWorkUtil.getInputStreamFromUrl(path); # if(is != null){ # Bitmap bm = BitmapFactory.decodeStream(new FlushedInputStream(is)); # return bm; # }else{ # return null; # } # } catch (Exception e) { # e.getStackTrace(); # System.out.println("asy is error :"+e.getMessage()); # return null; # } # } # # static class FlushedInputStream extends FilterInputStream { # public FlushedInputStream(InputStream inputStream) { # super(inputStream); # } # @Override # public long skip(long n) throws IOException { # long totalBytesSkipped = 0L; # while (totalBytesSkipped < n) { # long bytesSkipped = in.skip(n - totalBytesSkipped); # if (bytesSkipped == 0L) { # int b = read(); # if (b < 0) { # break; // we reached EOF # } else { # bytesSkipped = 1; // we read one byte # } # } # totalBytesSkipped += bytesSkipped; # } # return totalBytesSkipped; # } # } # public interface ImageCallback { # public void imageLoaded(Bitmap imageBitmap, String imageUrl); # } # } # -************************************************************************** # 在adapter里面使用： # final ImageView image = viewCache.image; # image.setTag(url); # # Bitmap cachedImage = asyncImageLoader.loadBitmap(url, new ImageCallback() { # public void imageLoaded(Bitmap imageDrawable, String imageUrl) { # image.setImageBitmap(imageDrawable); # } # }); # # if (cachedImage == null) { # image.setImageResource(R.drawable.icon); # }else{ # //image.setImageDrawable(cachedImage); # image.setImageBitmap(cachedImage); # }