無法添加窗口異常時，在getView方法的BaseAdapter中的按鈕單擊事件中使用Asynctask？

Question

當我的baseadapter的getView方法中單擊一個按鈕時，我無法在asynctask類的preexecute方法中顯示進度對話框。當pDialog.show（）方法ID調用我得到「無法添加窗口異常」例外。當我刪除preexecute方法時，它工作正常。有人可以解釋爲什麼發生這種情況。

這裏是我的代碼：

protected void onPreExecute() { 
     super.onPreExecute(); 
     pDialog = new ProgressDialog(context); 
     pDialog.setMessage("Please wait.."); 
     pDialog.setCancelable(false); 
     pDialog.show(); 
    } 

這是我的按鈕單擊事件代碼：

holder.buttonid.setOnClickListener(new OnClickListener() 
    { 
     @Override 
     public void onClick(View v) 
     { 
      try 
      { 
       new MyAsyncTask().execute();       
      } catch (Exception e) 
      { 
       e.printStackTrace(); 
      }    
     } 
    }); 

這是我BadeAdapter類

公共類FriendListAdapter延伸BaseAdapter {

private Context context; 
private LayoutInflater inflater=null; 

private ArrayList<MyObject> mDisplayedValues; 


static class ViewHolder 
{ 
    ImageView img_friend; 
    TextView tvname_friend; 
    Button btnstatus_friend; 
} 

public FriendListAdapter(Context context, ArrayList<MyObject> arrayList) { 
    inflater = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE); 
    this.context = context; 

    this.mDisplayedValues = arrayList; 

} 

@Override 
public int getCount() { 
    // TODO Auto-generated method stub 
    return mDisplayedValues.size(); 
} 

@Override 
public Object getItem(int position) { 
    // TODO Auto-generated method stub 
    return position; 
} 

@Override 
public long getItemId(int position) { 
    // TODO Auto-generated method stub 
    return position; 
} 

@Override 
public View getView(int position, View convertView, ViewGroup parent) { 

    View view =convertView; 
    ViewHolder holder = null; 


    if(convertView==null) 
    { 
     view = inflater.inflate(R.layout.inflate_view,parent,false); 
     holder = new ViewHolder(); 


     holder.buttonid= (Button)view.findViewById(R.id.btnid); 

     view.setTag(holder); 
    } 
    else 
    { 
     holder = (ViewHolder)view.getTag(); 
    } 
     try 
{ 



    holder.buttonid.setOnClickListener(new OnClickListener() 
{ 
    @Override 
    public void onClick(View v) 
    { 
     try 
     { 
      new MyAsyncTask().execute();       
     } catch (Exception e) 
     { 
      e.printStackTrace(); 
     }    
    } 
}); 

} catch (Exception e) 
{ 
     e.printStackTrace(); 
} 

    return view; 
} 




private class MyAsyncTask extends AsyncTask<String, Void, Void> { 

    private ProgressDialog pDialog = null; 

    private boolean hasExceptionOccured = false; 


    @Override 
    protected void onPreExecute() { 
     super.onPreExecute(); 
     pDialog = new ProgressDialog(context); 
     pDialog.setMessage("Please wait.."); 
     pDialog.setCancelable(false); 
     pDialog.show(); 

    } 

    @Override 
    protected Void doInBackground(String... params) { 
     // TODO Auto-generated method stub 
     //Intent to next activity 

     return null; 
    } 

    @Override 
    protected void onPostExecute(Void result) { 
     super.onPostExecute(result); 
     if (pDialog.isShowing()) 
      pDialog.dismiss(); 


    } 


} 



} 

Answer 1

您需要使用活動的情況下，顯示一個對話框

pDialog = new ProgressDialog(YourActivity.this); 

Here一些更多的信息。