android image cache 图片缓存 异步 下载

自动判断从内存还是网络获取图片,缓存自动回收import java.io.InputStream;import java.lang.ref.SoftReference;import java.net.URL;import java.net.URLConnection;import java.util.HashMap;import android.graphics.Bitmap;import android.graphics.BitmapFactory;/** *  * @author yizhe * @date 2012-6-13 */public class BitmapLoader {// 内存缓存,SoftReference实现自动回收private static HashMap<String, SoftReference<Bitmap>> imageCache = new HashMap<String, SoftReference<Bitmap>>();/** * 自动判断从内存还是从网络获取图片 *  * @param imageURL * @return */public static Bitmap loadBitmap(String imageURL) {Bitmap bm = null;if (imageCache.containsKey(imageURL)) {// 从内存中获取System.out.println("imageCache");SoftReference<Bitmap> reference = imageCache.get(imageURL);bm = reference.get();}if (null == bm) {// 到网络下载System.out.println("loadNetBitmap");bm = loadNetBitmap(imageURL);if (null != bm) {imageCache.put(imageURL, new SoftReference<Bitmap>(bm)); // 保存到内存}}return bm;}// 从网络下载图片private static Bitmap loadNetBitmap(String imageURL) {try {URL url = new URL(imageURL);URLConnection connection;connection = url.openConnection();Bitmap bitmap = BitmapFactory.decodeStream((InputStream) connection.getContent());return bitmap;} catch (Exception e) {}return null;}}