Unable to get visible/live Fragment

Question

I am stuck in this problem.

I want to maintain live instance of Fragment in application context. What I did is

1st Attempt

public class BaseProjectFragmentParent extends BaseProjectFragment {
    @Override
    public void onResume() {
        super.onResume();
        App.getInstance().setLiveFragment(this);
    }

    @Override
    public void onPause() {
        super.onPause();
        App.getInstance().setLiveFragment(null);
    }
}

and I extend all fragments by this base class. I expected live instance to be there in Application class.

Problem is in ViewPager, I have two Fragment in ViewPager where both Fragment's onResume() is called and live instance is set the second Fragment. I am working on some common code so I don't want to use getCurrentItem().

Second Attempt

Next I tried to get this Live Fragment by getSupportFragmentManager().getFragments()

1. isVisible() is true for both Fragments. (Not useful)
2. isResumed() is true for both Fragments. (Not useful)

Answer 1

You can use

setUserVisibleHint(boolean isVisibleToUser)

In fragments. This flag is set by the OS when a fragment becomes visible:

class MyFragment extends Fragment {

    public MyFragment() {
        setUserVisibleHint(false) //This is needed because by default its true 
    }

    @Override
    public void setUserVisibleHint(boolean isVisibleToUser) {
         super.setUserVisibleHint(isVisibleToUser)
         //true if fragment is visible
    }
}

However this wont get called inside Viewpager. You have to add a listener to the viewpager and then set your active page manually:

viewPager.addOnPageChangeListener(new OnPageChangeListener() {
public void onPageScrollStateChanged(int state) {}
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {}

public void onPageSelected(int position) {
    // Check if this is the page you want.
}
});