如何同时重新加载所有片段

Question

I have an activity with 2 fragments. Let's call the activity "MainActivity", the first fragment "FragmentA" and the second fragment "FragmentB". When I delete an element in FragmentA, I use this method inside the FragmentA to realod it:

public void reload_fragment() {
    FragmentTransaction ft = getFragmentManager().beginTransaction();
    ft.detach(this).attach(this).commit();
}

But I also need to reload the FragmentB at the same time. I try to add in the above method that:

public void reload_fragment() {
    FragmentTransaction ft = getFragmentManager().beginTransaction();
    ft.detach(this).attach(this).commit();
    MainActivity mainActivity = new MainActivity();
    mainActivity.reload_fragments();

And then, in my mainActivity, i have this method:

  public void reload_fragments(){
    viewPager = findViewById(R.id.Viewpager_ID);

    adapter = new SimpleFragmentPagerAdapter(getSupportFragmentManager());
    viewPager.setAdapter(adapter);
    TabLayout tabLayout = findViewById(R.id.tablayout);
    tabLayout.setupWithViewPager(viewPager);
}

But it doesn't work. I tried to add the same method which is inside the FragmentA into the FragmentB, and then call it by the FragmentA, but again, it says "virtual method on NullObjectReference". How can I refresh all the fragments at the same time?

Answer 1

Form a ViewModel with a MutableLiveData boolean field called say "refresh". Add a method to the ViewModel called "toggleRefresh()" which flips the state of refresh. In each fragment, in the onAttatch, observe the refresh field and do the "reload there"?