title: application may be doing too much work on main thread even after using a different thread
body: <p>Hello I am new to android and is following a yamba application which posts and get status from the twitter. I was working fine before I added the new part.</p>
  
  <p>I used a different thread to perform the post. But once I run the project, logcat says"application may be doing too much work on main thread".When I type in status,"thread exiting with uncaught exception",due to NullPointException in this doInBackGround method.</p>
  
  <p>Anyone can help me??I have even registered a Twitter account to make sure it is not null.But Thanks alot for any answer!!</p>
  
  <pre><code>    public class MainActivity extends Activity implements OnClickListener,TextWatcher
      {
      private static final String TAG="StatusActivity";
      EditText editText;
      Button buttonUpdate;
      TextView textCount;
      private YambaApplication yamba;
  
  
  //constructor
       @Override
    public void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
  
  editText=(EditText) findViewById(R.id.editText);
  buttonUpdate=(Button) findViewById(R.id.buttonUpdate);
  textCount=(TextView) findViewById(R.id.textCount);
  textCount.setText(Integer.toString(140));
  textCount.setTextColor(Color.GREEN);
  
  buttonUpdate.setOnClickListener(this);
  editText.addTextChangedListener(this);
  this.yamba=(YambaApplication)getApplication();
  }   
  
  
      //Main task of posting, three method of AsyncTask
  class PostToTwitter extends AsyncTask&lt;String,Integer,String&gt;
  {
      @Override
      protected String doInBackground(String...statuses)
      {
          try{
               Twitter.Status status=yamba.getTwitter().updateStatus(statuses[0]);
               return status.text;
          }
          catch(TwitterException e){
              Log.e(TAG, e.toString());
              e.printStackTrace();
              return "Failed to post";
          }
      }
  </code></pre>
  
  <p>There is this task in the yamba application java:</p>
  
  <pre><code>    public synchronized Twitter getTwitter(){
      if(twitter==null)
      {
          String username,password,APIroot;
          username=prefs.getString("username", "");
          password=prefs.getString("passord", "");
          APIroot=prefs.getString("APIroot", "http://yamba.marakana.com/api");
  
       if ( !TextUtils.isEmpty(username) &amp;&amp; !TextUtils.isEmpty(password) &amp;&amp; !TextUtils.isEmpty(APIroot) )
           {
              twitter= new Twitter(username,password);
               twitter.setAPIRootUrl(APIroot);
            }
       }
      return this.twitter;
    } 
  </code></pre>