android 异步下载图片
SyncImageLoader 图片异步下载工具类?
package mars.async.down.utils;import java.lang.ref.SoftReference;import java.net.URL;import java.util.HashMap;import android.graphics.drawable.Drawable;import android.os.Handler;import android.os.Message;public class SyncImageLoader {private HashMap<String, SoftReference<Drawable>> imageCache = new HashMap<String, SoftReference<Drawable>>();// 根据URL从网络上下载图片,生成Drawable对象public Drawable loadImageFormUrl(String imageUrl) {try {return Drawable.createFromStream(new URL(imageUrl).openStream(),"src");} catch (Exception e) {e.printStackTrace();throw new RuntimeException(e);}}public Drawable loadDrawable(final String imageUrl,final ImageCallback imageCallback) {// 判断缓存中是否有imageUrl这个缓存存在if (imageCache.containsKey(imageUrl)) {SoftReference<Drawable> softReference = imageCache.get(imageUrl);if (softReference.get() != null) {return softReference.get();}}final Handler handler = new Handler() {@Overridepublic void handleMessage(Message msg) {imageCallback.imageLoaded((Drawable) msg.obj);}};// 缓存中不存在的话,启动异步线程下载图片new Thread() {@Overridepublic void run() {// 将图片放入缓存Drawable drawable = loadImageFormUrl(imageUrl);imageCache.put(imageUrl, new SoftReference<Drawable>(drawable));Message msg = handler.obtainMessage(0, drawable);handler.sendMessage(msg);}}.start();return null;}// 回调函数,图片加载完毕后调用该函数public interface ImageCallback {public void imageLoaded(Drawable imageDrawable);}}?
CallbackImplements 回调接口实现类。
package mars.async.down.utils;import android.graphics.drawable.Drawable;import android.widget.ImageView;public class CallbackImplements implements SyncImageLoader.ImageCallback {private ImageView imageView;public CallbackImplements(ImageView imageView) {super();this.imageView = imageView;}@Overridepublic void imageLoaded(Drawable imageDrawable) {imageView.setImageDrawable(imageDrawable);}}?
在Activity中调用
package mars.async.down;import mars.async.down.utils.CallbackImplements;import mars.async.down.utils.SyncImageLoader;import android.app.Activity;import android.graphics.drawable.Drawable;import android.os.Bundle;import android.widget.ImageView;public class MainActivity extends Activity {private SyncImageLoader syncImageLoader = new SyncImageLoader();@Overridepublic void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.main);loadImage("http://www.android.com/images/icon-partners.png",R.id.imageView1);loadImage("http://www.android.com/images/icon-dev.png", R.id.imageView2);loadImage("http://www.android.com/images/icon-market.png",R.id.imageView3);}// url:图片的url地址// id:ImageView控件的IDprivate void loadImage(String url, int id) {ImageView imageView = (ImageView) findViewById(id);CallbackImplements callbackImplements = new CallbackImplements(imageView);Drawable cacheImage = syncImageLoader.loadDrawable(url,callbackImplements);// 如果图片缓存存在,则在外部设置image.否则是调用的callback函数设置if (cacheImage != null) {imageView.setImageDrawable(cacheImage);}}}?