listview 图片异步加载 的实现并缓存到内存 和本地sdcard 中
package com.dodoyota.weicom.net;import java.io.File;import java.io.FileInputStream;import java.io.FileOutputStream;import java.lang.ref.SoftReference;import java.net.URL;import java.util.HashMap;import java.util.Map;import java.util.concurrent.ExecutorService;import java.util.concurrent.Executors;import android.graphics.drawable.Drawable;import android.os.Environment;import android.os.Handler;import android.util.Log;import com.weibo.sdk.android.util.FormatTools;import com.weibo.sdk.android.util.MD5Utils;/** * 异步加载图片 * @author 高元东 * @mailto 466862016@qq.com * 2013-6-20 下午9:58:57 */public class AsyncImageLoader {public Map<String, SoftReference<Drawable>> imageCache = new HashMap<String, SoftReference<Drawable>>();private static ExecutorService executorService = Executors.newFixedThreadPool(5);private final Handler handler = new Handler();/*** * 异步加载图片 * @mailto 466862016@qq.com * 2013-6-20 下午10:01:34 * @param imageUrl * @param callback * @return */public Drawable loadDrawable(final String imageUrl,final ImageCallback callback) {// 如果缓存过就从缓存中取出数据if (imageCache.containsKey(MD5Utils.encode(imageUrl))) {SoftReference<Drawable> softReference = imageCache.get(MD5Utils.encode(imageUrl));if (softReference.get() != null) {Log.i("imageloader", "从缓存中获取图片");return softReference.get();}}//sdcard 可用使用 if(this.checkSdcard()) { Drawable drawable = null; File dir = new File(Environment.getExternalStorageDirectory()+"/weicom"); if(!dir.exists()) { dir.mkdir(); } File header = new File(dir, MD5Utils.encode(imageUrl)); if(header.exists()) { FileInputStream fileInputStream = null;try {fileInputStream = new FileInputStream(header);//从sdcard 中取数据 drawable = Drawable.createFromStream(fileInputStream, "ayscimage"); Log.i("imageloader", "从sdcard获取图片"); if(!imageCache.containsKey(MD5Utils.encode(imageUrl))) { //在sdcard 中取出的图片放在缓存中 imageCache.put(MD5Utils.encode(imageUrl), new SoftReference<Drawable>(drawable)); } return drawable;} catch (Exception e) {e.printStackTrace();} } }// 缓存中没有图像，则从网络上取出数据，并将取出的数据缓存到内存中executorService.submit(new Runnable() {public void run() {try {final Drawable drawable = loadImageFromUrl(imageUrl); imageCache.put(imageUrl, new SoftReference<Drawable>(drawable)); Log.i("imageloader", "将图片保存在缓存中");/*** * 保存在sdcard 中 */if(checkSdcard()) { File dir = new File(Environment.getExternalStorageDirectory()+"/weicom"); if(!dir.exists()) { dir.mkdir(); } File header = new File(dir, MD5Utils.encode(imageUrl)); FileOutputStream fileOutputStream = new FileOutputStream(header); FormatTools formatTools = FormatTools.getInstance(); byte[] by = formatTools.Drawable2Bytes(drawable); fileOutputStream.write(by); fileOutputStream.flush(); Log.i("imageloader", "将图片保存在sdcard "); }handler.post(new Runnable() {public void run() {callback.imageLoaded(drawable);}});} catch (Exception e) {throw new RuntimeException(e);}}});return null;}/*** * 按照 url 从网络上获取 图片 * @mailto 466862016@qq.com * 2013-6-20 下午10:00:40 * @param imageUrl * @return */protected Drawable loadImageFromUrl(String imageUrl) {try {Log.i("imageloader", "从网络中获取图片");return Drawable.createFromStream(new URL(imageUrl).openStream(),"iamgeSync");} catch (Exception e) {throw new RuntimeException(e);}}/*** * 检查sdcard 是否可用 * @mailto 466862016@qq.com * 2013-6-20 下午10:08:18 * @return */private boolean checkSdcard() {String status = Environment.getExternalStorageState();if(status.equals(Environment.MEDIA_MOUNTED)) {return true;}return false;}/*** * 对外开放的接口 * @author 高元东 * @mailto 466862016@qq.com * 2013-6-20 下午10:00:03 */public interface ImageCallback {public void imageLoaded(Drawable imageDrawable);}}?