如何將這些方法放入異步任務？

Question

我想在一個asynctask中運行這些方法，所以它不會阻止我的主UI。

有人可以舉例說明如何做到這一點？

07-20 17:36:44.550: ERROR/AndroidRuntime(589): Caused by: android.view.ViewRoot$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views. 


public void getImages() throws IOException{ 

    DefaultHttpClient httpclient = new DefaultHttpClient(); 

    HttpGet httppost = new HttpGet("https://sites.google.com/site/theitrangers/images/webImages.txt"); 
    HttpResponse response; 

     response = httpclient.execute(httppost); 


      HttpEntity ht = response.getEntity(); 

      BufferedHttpEntity buf = new BufferedHttpEntity(ht); 

      InputStream is = buf.getContent(); 


      BufferedReader r = new BufferedReader(new InputStreamReader(is)); 

      StringBuilder total = new StringBuilder(); 
      String line; 
      while ((line = r.readLine()) != null) { 
       total.append(line + "\n"); 

       imageUrl = total.toString(); 
      } 

      } 
      public void getImage2() throws IOException{ 

       DefaultHttpClient httpclient = new DefaultHttpClient(); 

       HttpGet httppost = new HttpGet("https://sites.google.com/site/theitrangers/images/webImage2.txt"); 
       HttpResponse response; 

        response = httpclient.execute(httppost); 


         HttpEntity ht = response.getEntity(); 

         BufferedHttpEntity buf = new BufferedHttpEntity(ht); 

         InputStream is = buf.getContent(); 


         BufferedReader r = new BufferedReader(new InputStreamReader(is)); 

         StringBuilder total = new StringBuilder(); 
         String line; 
         while ((line = r.readLine()) != null) { 
          total.append(line + "\n"); 

          imageUrl2 = total.toString(); 

         } 

} 
      public class ImageAdapter extends BaseAdapter { 
       /** The parent context */ 
       private Context myContext;public ImageAdapter() { 
        // TODO Auto-generated constructor stub 
       } 
       /** URL-Strings to some remote images. */ 

       private String[] myRemoteImages = {imageUrl,imageUrl2}; 






       /** Simple Constructor saving the 'parent' context. */ 
       public ImageAdapter(Context c) { this.myContext = c; } 

       public ImageAdapter(MyTask myTask) { 
        // TODO Auto-generated constructor stub 
       } 

       /** Returns the amount of images we have defined. */ 
       public int getCount() { return this.myRemoteImages.length; } 

       /* Use the array-Positions as unique IDs */ 
       public Object getItem(int position) { return position; } 
       public long getItemId(int position) { return position; } 

       /** Returns a new ImageView to 
       * be displayed, depending on 
       * the position passed. */ 
       public View getView(int position, View convertView, ViewGroup parent) { 
       ImageView i = new ImageView(this.myContext); 

       try { 
           /* Open a new URL and get the InputStream to load data from it. */ 
           URL aURL = new URL(myRemoteImages[position]); 
           URLConnection conn = aURL.openConnection(); 
           conn.connect(); 
           InputStream is = conn.getInputStream(); 
           /* Buffered is always good for a performance plus. */ 
           BufferedInputStream bis = new BufferedInputStream(is); 
           /* Decode url-data to a bitmap. */ 
           Bitmap bm = BitmapFactory.decodeStream(bis); 
           bis.close(); 
           is.close(); 

           /* Apply the Bitmap to the ImageView that will be returned. */ 
           i.setImageBitmap(bm); 
         } catch (IOException e) { 

           Log.e("DEBUGTAG", "Remtoe Image Exception", e); 
         } 

       /* Image should be scaled as width/height are set. */ 
       i.setScaleType(ImageView.ScaleType.FIT_CENTER); 
       /* Set the Width/Height of the ImageView. */ 
       i.setLayoutParams(new Gallery.LayoutParams(150, 150)); 
       return i; 
       } 

       /** Returns the size (0.0f to 1.0f) of the views 
       * depending on the 'offset' to the center. */ 
       public float getScale(boolean focused, int offset) { 
       /* Formula: 1/(2^offset) */ 
       return Math.max(0, 1.0f/(float)Math.pow(2, Math.abs(offset))); 
       } 
       } 






       private class MyTask extends AsyncTask<Void, Void, Void>{ 

       protected void onPreExecute(){ 

        String imageUrl = null; 
         String imageUrl2 = null; 
       } 

       @Override 
       protected Void doInBackground(Void... arg0) { 

        try { 
          getImages(); 
          getImage2(); 
         } catch (IOException e) { 
          Log.e("MainMenu retreive image", "Image Retreival failed"); 
          e.printStackTrace(); 
         } 
         ((Gallery) findViewById(R.id.gallery)) 
         .setAdapter(new ImageAdapter(this)); 
        return null; 
       } 

} 

}

Answer 1

This guide會解釋你需要開始使用的AsyncTask的一切。

總結：

• 把網絡讀取/耗時碼doInBackground
• 過程的輸出在UI線程在onPostExecute

Answer 2

你所得到的錯誤是「只有創建視圖層次結構的原始線程可以觸及其視圖。「

而這個錯誤是因爲你正在修改另一個線程中的UI，所以要解決這個問題，你只需要像這樣更新UI。

Activityname.this.runOnUiThread(new Runnable() { 

     @Override 
     public void run() { 

      update the UI here...... 

     } 
    });