android how to setOnClickListener for fragment button

Question

I have an activity and a fragment. The fragment has a button on it.

I load the fragment:

fragment = new FragmentPIN(this);                   
fragmentTransaction.add(R.id.content,fragment);         
fragmentTransaction.commit();

then try to set the listener

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

        Button cmdOK_PIN = (Button)activity.findViewById(R.id.cmdOK_PIN);
        cmdOK_PIN.setOnClickListener(new View.OnClickListener() {                       
            @Override
            public void onClick(View v) {

            }

        });

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

But I always get a null pointer exception on the setOnClickListener call. The fragment transaction is committed before I attempt to set the listener. Or I think it is. Should I be using another override to do this?

Solution 1

Try changing where you set the listener to the onActivityCreated instead of onAttach. According to the Android docs:

onActivityCreated is called when the fragment's activity has been created and this fragment's view hierarchy instantiated.

When you call onAttach that's before the Activity has setup its view

Solution 2

Hi im new to android and was getting that nullpointer exception when I added some buttons dynamically. Fragment also has a method onViewCreated you can override. Guessing from its name you can be sure the view is there :)

@Override
public void onViewCreated(View view, Bundle savedInstanceState) {

    super.onViewCreated(view, savedInstanceState);
    }