Child Fragment's setUserVisibleHint and onResume not called

Question

I am trying to call a function when user switch the page to my child fragment. But, when I try to use setUserVisibleHint and onResume, both functions are called from my parent fragment.

First, I set up a view pager in Activity

Then in A1, A3 and B1, I have setUserVisibleHint and onResume functions.

setUserVisibleHint and onResume functions

@Override
public void setUserVisibleHint(boolean visible) {
    super.setUserVisibleHint(visible);
    Log.d("A1", "setUserVisibleHint"); // A3 for Fragment A3 and B1 for Fragment B1 
    if (visible && isResumed())
        onResume();
}
@Override
public void onResume() {
    super.onResume();
    Log.d("A1", "onResume"); // A3 for Fragment A3 and B1 for Fragment B1 
    if (!getUserVisibleHint())
        return;
}

Issues:

When I click page B from page A and the view is Fragment B1, I get (This is OK)

D/A1: setUserVisibleHint
D/B1: setUserVisibleHint
D/B1: onResume

When I click page A from page B and the view is Fragment A1, I get (This is OK)

D/B1: setUserVisibleHint
D/A1: setUserVisibleHint
D/A1: onResume

When I click page A from page B and the view is Fragment A3, I get (ISSUE)

D/B1: setUserVisibleHint
D/A1: setUserVisibleHint
D/A1: onResume

I assume that the printout should be like below but I am not sure why the functions called by parent fragment.

D/B1: setUserVisibleHint
D/A3: setUserVisibleHint
D/A3: onResume

Reference

From fragment A1 -> A2,

A2 a2 = new A2();
getFragmentManager().beginTransaction().add(R.id.A1_frameChildFragment, a2)
    .addToBackStack(null)
    .commit();

From fragment A2 -> A3,

A3 a3 = new A3();
getFragmentManager().beginTransaction().add(R.id.A2_frameChildFragment, a3)
    .addToBackStack(null)
    .commit();

Answer 1

onResume will not called when you switch between tab in ViewPager.
setUserVisibleHint will called in the parent fragment of each tab when you switch between in ViewPager and will not called in child fragment.
This is the default behavior so I think we can not change it.

However, there is a workaround solution. It is sending the visible hint from parent fragment to child fragment

// visible hint in parent fragment
@Override
public void setUserVisibleHint(boolean isVisibleToUser) {
    super.setUserVisibleHint(isVisibleToUser);
    if (!isAdded()) {
        return;
    }
    Fragment fragment = getChildFragmentManager().findFragmentById(R.id.A1_frameChildFragment); // find current child fragment
    if (fragment != null) {
        fragment.setUserVisibleHint(isVisibleToUser); // send visible from parent to this child fragment
    }
}