如何在Android中異步顯示來自服務器的圖像？

Question

我在Android中顯示來自服務器的圖像。爲此我已經通過了教程Android Load Image From URL Example。這非常有幫助。但從服務器顯示圖像需要5分鐘的時間。所以我想要異步顯示圖像。我怎樣才能做到這一點？

Answer 1

試試Lazy Loading中的示例鏈接。

Answer 2

以下代碼段將幫助您。

DownloadHelper.java

public interface DownloadHelper 
{ 
    public void OnSucess(Bitmap bitmap); 
    public void OnFailure(String response); 
} 

MainActivity.java

public class GalleryExample extends Activity { 
    /** Called when the activity is first created. */ 
    @Override 
    public void onCreate(Bundle icicle) { 
     super.onCreate(icicle); 
     setContentView(R.layout.main); 

     DownloadHelper downloadHelper = new DownloadHelper() 
     { 
      @Override 
      public void OnSucess(Bitmap bitmap) 
      { 
       ImageView imageView=(ImageView)findViewById(R.id.imageView); 
       imageView.setImageBitmap(bitmap); 
      } 

      @Override 
      public void OnFailure(String response) 
      { 
       Toast.makeText(context, response, Toast.LENGTH_LONG).show(); 
      } 
     }; 
     new MyTask(this,downloadHelper).execute("image url"); 
    } 

MyTask.java

public class DownloadTask extends AsyncTask<String, Integer, Object> 
{ 
    private Context context; 
    private DownloadHelper downloadHelper; 
    private ProgressDialog dialog; 


    public DownloadTask(Context context,DownloadHelper downloadHelper) 
    { 
     this.context = context; 

    } 

    @Override 
    protected void onPreExecute() 
    { 
     dialog = new ProgressDialog(context); 
     dialog.setTitle("Please Wait"); 
     dialog.setMessage("Fetching Data!!"); 
     dialog.setCancelable(false); 
     dialog.show(); 
     super.onPreExecute(); 
    } 

    @Override 
    protected Object doInBackground(String... params) 
    { 
     URL aURL = new URL(myRemoteImages[position]); 
     URLConnection conn = aURL.openConnection(); 
     conn.connect(); 
     InputStream is = conn.getInputStream(); 

     BufferedInputStream bis = new BufferedInputStream(is); 
     /* Decode url-data to a bitmap. */ 
     Bitmap bm = BitmapFactory.decodeStream(bis); 
     bis.close(); 
     is.close(); 
     return bm; 
    } 

    @Override 
    protected void onPostExecute(Object result) 
    { 
     dialog.dismiss(); 
     if (result != null) 
     { 
      downloadHelper.OnSucess((Bitmap)result); 
     } 
     else 
     { 
      downloadHelper.OnFailure("Error in Downloading Data!!"); 
     } 
     super.onPostExecute(result); 
    } 
}