轉載自： http://doinone.iteye.com/blog/1074283

android中獲取網路圖片是一件耗時的操作，如果直接獲取有可能會出現應用程式無響應（ANR:Application Not Responding）對話方塊的情況。對於這種情況，一般的方法就是耗時操作用執行緒來實現。下面列三種獲取url圖片的方法： 
1.直接獲取：（容易：ANR，不建議）

mImageView = (ImageView)this.findViewById(R.id.imageThreadConcept) ;
Drawable drawable = loadImageFromNetwork(IMAGE_URL);
mImageView.setImageDrawable(drawable) ;
 

private Drawable loadImageFromNetwork(String imageUrl)
{
	Drawable drawable = null;
	try {
		// 可以在這裡通過檔名來判斷，是否本地有此圖片
		drawable = Drawable.createFromStream(
				new URL(imageUrl).openStream(), "image.jpg");
	} catch (IOException e) {
		Log.d("test", e.getMessage());
	}
	if (drawable == null) {
		Log.d("test", "null drawable");
	} else {
		Log.d("test", "not null drawable");
	}
	
	return drawable ;
}
 

mImageView = (ImageView)this.findViewById(R.id.imageThreadConcept) ;
new Thread(new Runnable(){
	Drawable drawable = loadImageFromNetwork(IMAGE_URL);
	@Override
	public void run() {
		
	    // post() 特別關鍵，就是到UI主執行緒去更新圖片				
	    mImageView.post(new Runnable(){
		@Override
		public void run() {
		    // TODO Auto-generated method stub
		    mImageView.setImageDrawable(drawable) ;
		}}) ;
		}
		
}).start()  ;
 

3.AsyncTask獲取url圖片

mImageView = (ImageView)this.findViewById(R.id.imageThreadConcept) ;
new DownloadImageTask().execute(IMAGE_URL) ;
private class DownloadImageTask extends AsyncTask<String, Void, Drawable> 
{
	    
	    protected Drawable doInBackground(String... urls) {
	        return loadImageFromNetwork(urls[0]);
	    }

	    protected void onPostExecute(Drawable result) {
	        mImageView.setImageDrawable(result);
	    }
}