Android實現圖片的異步載入顯示

AsyncImageLoader.java

import java.io.InputStream;
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;
import android.widget.ImageView;
/**

實現圖片的異步載入顯示
@author kandanle
/
public class AsyncImageLoader {
/**

軟引用對象，在響應內存需要時，由垃圾回收器決定是否清除此對象。軟引用對象最常用于實現內存敏感的緩存。
*/
private HashMap<String, SoftReference<Drawable>> imageCache;
public AsyncImageLoader(){
 imageCache = new HashMap<String, SoftReference<Drawable>>();
}
public Drawable loadDrawable(final String imageUrl,final ImageView imageView,final ImageCallback imagecallback){
 if(imageCache.containsKey(imageUrl)){

 //從緩存中讀取人人
 SoftReference<Drawable> softReference = imageCache.get(imageUrl);
 Drawable drawable = softReference.get();
 if(drawable != null){
     return drawable;
 }

}
 final Handler handler = new Handler(){

 @Override
 public void handleMessage(Message msg) {
     super.handleMessage(msg);
     imagecallback.imageLoaded((Drawable)msg.obj, imageView, imageUrl);
 }

};
 new Thread(){

 public void run() {
     Drawable drawable = loadImageFromUrl(imageUrl);
     imageCache.put(imageUrl, new SoftReference<Drawable>(drawable));
     Message message = handler.obtainMessage(0, drawable);
     handler.sendMessage(message);
 }

}.start();
return null;
}
public static Drawable loadImageFromUrl(String urlPath){
 URL url;
 InputStream is = null;
 try{

 url = new URL(urlPath);
 is = (InputStream)url.getContent();

}catch(Exception e){

 e.printStackTrace();

}
 Drawable drawable = Drawable.createFromStream(is, "src");
 return drawable;
}




}</pre> 


 ImageCallback.java 

import android.graphics.drawable.Drawable;
import android.widget.ImageView;

public interface ImageCallback {
    public void imageLoaded(Drawable imageDrawable,ImageView imageView, String imageUrl);
}
Drawable drawable = asyncImageLoader.loadDrawable(weiboInfo.getUserIcon(), viewUserIcon, new ImageCallback() {
    @Override
    public void imageLoaded(Drawable imageDrawable, ImageView imageView,String imageUrl) {
    imageView.setImageDrawable(imageDrawable);
        }
});
if(drawable == null){
    viewUserIcon.setImageResource(R.drawable.portrait);
}else{
    viewUserIcon.setImageDrawable(drawable);
}</pre>