CODEWITHSUNDEEP
androidmultithreadingandroid-fragmentshandler
Kevik
Kevik

Reputation: 9351

null pointer on thread handler inside fragment

I wanted to run this fragment as a background thread so any processing done does not effect the main UI thread, however I am getting a null pointer exception on the line

 handler.post(new Runnable() {

I am lost, how do i fix this? here is the stack trace

07-15 09:34:36.534: E/AndroidRuntime(6905): FATAL EXCEPTION: Thread-5235 07-15 09:34:36.534: E/AndroidRuntime(6905): java.lang.NullPointerException 07-15 09:34:36.534: E/AndroidRuntime(6905): at com.example.asynctaskprogressbarexample.FragmentHeadlessFragment$1.run(FragmentHeadlessFragment.java:37)

the rest of the code

 public class FragmentHeadlessFragment extends Fragment {

private OnTimeRequestedListener listener;
Activity activity;
Handler handler;

@Override
public void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);

    new Thread(){

        public void run() {

        SystemClock.sleep(3000);

        handler.post(new Runnable() {  // <-- NULL POINTER EXCEPTION THIS LINE
            @Override
            public void run() {

                passData("test string from fragment with 3 second delay");
            }
         });


         } // end run

  }.start(); 


} // end onCreate

 @Override
  public void onAttach(Activity activity) {
    super.onAttach(activity);

    if (activity instanceof OnTimeRequestedListener) {
      listener = (OnTimeRequestedListener) activity;
    } else {
      throw new ClassCastException(activity.toString()
          + " must implement OnTimeRequestedListener");
    }
  }

@Override
 public void onActivityCreated(Bundle savedInstanceState) {
  super.onActivityCreated(savedInstanceState);
  activity = getActivity();
  setRetainInstance(true);


 }

 public interface OnTimeRequestedListener {
        public void passSystemTime(String timeNumberString);

  }

 public void passData(String data) {
        listener.passSystemTime(data);
    }


}

Upvotes: 1

Views: 2099

Answers (2)

Jeremy Trujillo
Jeremy Trujillo

Reputation: 54

You never initialized handler you can call Handler handler =getWindow().getDecorView().getHandler();

Upvotes: 0

user2579943
user2579943

Reputation:

You don't seem to have initialized handler in onCreate().

Upvotes: 1

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