How to get existing fragments when using FragmentP

Question

I have problem making my fragments communicating with each other through the Activity, which is using the FragmentPagerAdapter, as a helper class that implements the management of tabs and all details of connecting a ViewPager with associated TabHost. I have implemented FragmentPagerAdapter just as same as it is provided by the Android sample project Support4Demos.

The main question is how can I get particular fragment from FragmentManager when I don't have neither Id or Tag? FragmentPagerAdapter is creating the fragments and auto generating the Id and Tags.

Answer 1

I created this method which is working for me to get a reference to the current fragment.

public static Fragment getCurrentFragment(ViewPager pager, FragmentPagerAdapter adapter) {
    try {
        Method m = adapter.getClass().getSuperclass().getDeclaredMethod("makeFragmentName", int.class, long.class);
        Field f = adapter.getClass().getSuperclass().getDeclaredField("mFragmentManager");
        f.setAccessible(true);
        FragmentManager fm = (FragmentManager) f.get(adapter);
        m.setAccessible(true);
        String tag = null;
        tag = (String) m.invoke(null, pager.getId(), (long) pager.getCurrentItem());
        return fm.findFragmentByTag(tag);
    } catch (NoSuchMethodException e) {
        e.printStackTrace();
    } catch (IllegalArgumentException e) {
        e.printStackTrace();
    } catch (IllegalAccessException e) {
        e.printStackTrace();
    } catch (InvocationTargetException e) {
        e.printStackTrace();
    } catch (NoSuchFieldException e) {
        e.printStackTrace();
    } 
    return null;
}

Answer 2

I don't know if this is the best approach but nothing else worked for me. All other options including getActiveFragment returned null or caused the app to crash.

I noticed that on screen rotation the fragment was being attached so I used it to send the fragment back to the activity.

In the fragment:

@Override
public void onAttach(Activity activity) {
    super.onAttach(activity);
    try {
        mListener = (OnListInteractionListener) activity;
        mListener.setListFrag(this);
    } catch (ClassCastException e) {
        throw new ClassCastException(activity.toString()
                + " must implement OnFragmentInteractionListener");
    }
}

Then in the activity:

@Override
public void setListFrag(MyListFragment lf) {
    if (mListFragment == null) {
        mListFragment = lf;
    }
}

And finally in activity onCreate():

if (savedInstanceState != null) {
    if (mListFragment != null)
        mListFragment.setListItems(items);
}

This approach attaches the actual visible fragment to the activity without creating a new one.