URL로 이미지 불러와서 imagview 에 보여주는 걸 하고 있습니다.

AsyncTask 없이는 잘되었는데요. 다이얼로그 하려고 AsyncTask 로직 넣고 하니까

이미지는 안뜨고 false 가 나오고 로딩되다가 강제종료 창 뜹니다.ㅠㅠ

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package com.helloworld.com;

import java.io.BufferedInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.net.URLConnection;

import android.app.Activity;
import android.app.ProgressDialog;

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.DisplayMetrics;
import android.util.Log;
import android.widget.ImageView;

public class HelloActivity extends Activity{
 
  public void onCreate(Bundle savedInstanceState) {
  Log.w("DevLog", "onCreate");
  super.onCreate(savedInstanceState);
  setContentView(R.layout.main);
    
  MyAsyncTask task = new MyAsyncTask();
  task.execute();
 }
 
class MyAsyncTask extends AsyncTask <Void, Void, Void> {
        private ProgressDialog dialog;
  
  @Override
        protected Void doInBackground(Void... params) {
      String Resized = "http://www.gomonews.com/wp-content/uploads/2009/07/android-logo.jpg";
      ImageView iv = (ImageView)findViewById(R.id.ImageV);

         try { 
       URL aURL = new URL(Resized);                              
       URLConnection conn = aURL.openConnection();                            
       conn.connect();
                                 
       InputStream is = conn.getInputStream();
       BufferedInputStream bis = new BufferedInputStream(is);                        
       Bitmap bm = BitmapFactory.decodeStream(bis);    
       
       bis.close();                       
       is.close();
       
       DisplayMetrics dm = new DisplayMetrics();
       getWindowManager().getDefaultDisplay().getMetrics(dm);

       int newHeight = (int)((float)dm.widthPixels / (float)bm.getWidth() * (float)bm.getHeight());
       
       Bitmap bmresized = Bitmap.createScaledBitmap(bm, dm.widthPixels, newHeight, true);
       iv.setImageBitmap(bmresized);  
       }
       catch (IOException e) {     
       Log.e("DevLog", "Remtoe Image Exception", e);
       e.printStackTrace();           
       }
            dialog.dismiss();
            return null;
        }
     
  @Override
        protected void onPreExecute() {
         ProgressDialog.show(HelloActivity.this,"","loading",true);
            super.onPreExecute();
        }
       
  @Override
        protected void onPostExecute(Void result) {
         Log.w("DevLog", "onPostExecute");
            dialog.dismiss();
            super.onPostExecute(result);
        }  
      
    }

}

===============================================
12-24 03:26:47.615: WARN/dalvikvm(4523): threadid=13: thread exiting with uncaught exception (group=0x4001d1c8)
12-24 03:26:47.615: ERROR/AndroidRuntime(4523): Uncaught handler: thread AsyncTask #1 exiting due to uncaught exception
12-24 03:26:47.623: ERROR/AndroidRuntime(4523): java.lang.RuntimeException: An error occured while executing doInBackground()
12-24 03:26:47.623: ERROR/AndroidRuntime(4523):     at android.os.AsyncTask$3.done(AsyncTask.java:200)
12-24 03:26:47.623: ERROR/AndroidRuntime(4523):     at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:273)
12-24 03:26:47.623: ERROR/AndroidRuntime(4523):     at java.util.concurrent.FutureTask.setException(FutureTask.java:124)
12-24 03:26:47.623: ERROR/AndroidRuntime(4523):     at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:307)
12-24 03:26:47.623: ERROR/AndroidRuntime(4523):     at java.util.concurrent.FutureTask.run(FutureTask.java:137)
12-24 03:26:47.623: ERROR/AndroidRuntime(4523):     at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1068)
12-24 03:26:47.623: ERROR/AndroidRuntime(4523):     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:561)
12-24 03:26:47.623: ERROR/AndroidRuntime(4523):     at java.lang.Thread.run(Thread.java:1096)
12-24 03:26:47.623: ERROR/AndroidRuntime(4523): Caused by: java.lang.NullPointerException
12-24 03:26:47.623: ERROR/AndroidRuntime(4523):     at com.helloworld.com.HelloActivity$MyAsyncTask.doInBackground(HelloActivity.java:55)
12-24 03:26:47.623: ERROR/AndroidRuntime(4523):     at com.helloworld.com.HelloActivity$MyAsyncTask.doInBackground(HelloActivity.java:1)
12-24 03:26:47.623: ERROR/AndroidRuntime(4523):     at android.os.AsyncTask$2.call(AsyncTask.java:185)
12-24 03:26:47.623: ERROR/AndroidRuntime(4523):     at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
12-24 03:26:47.623: ERROR/AndroidRuntime(4523):     ... 4 more