Android Access Fragment Variable

You need to implement listeners. You can read more about here:Communicating with Other Fragments

Here is a code example how to pass data (or null) from Activity to a Fragment:

public class FragmentA extends Fragment implements FragmentCommunicator{


@Override
public void onAttach(Activity activity) {
    super.onAttach(activity);
    ((MainActivity)getActivity()).fragmentCommunicator = this;

}
@Override
public void passDataToFragment(String str) {
    //str is the string variable you pass from the Activity, it can be null...

    }
}}

Next the FragmentCommunicator Class:

public interface FragmentCommunicator{
public void passDataToFragment(String str);}

And the Activity:

 public class MainActivity extends FragmentActivity{

public FragmentCommunicator fragmentCommunicator;


public void someMethod(String someString) {

 fragmentCommunicator.passDataToFragment(someString);


}}

When you call passDataToFragment() from the Activity it will pass the string (or any other variable) to the fragment method passDataToFragment().

You can get your fragment by id/tag from fragment manager and do whatever you want with them.

that's super easy. if you are adding your fragments in runtime (using FragmentManager) you are creating objects of that fragment...just keep the reference with you and you are good to call any function or access any variable of the fragment. e.g. you fragment is MyFragment

MyFragment mf = new MyFragment();

getSupportFragmentManger().beginTrans......you know the code to add a fragment then simply call any method...for say... change() by mf.change();

or you can do something like

MyFragment mf = (MyFragment) findFragmentById(R.id.container);
and then again mf.change();