android - Bring Fragment to Front (No fragment recreation)

Question

I have three fragments F1 F2 F3 F4 all are accessible from sidebar.

all four can be called at any time and in any order,

Now I want if, F1 is already clicked(created) then never again create F1, but only bring back fragment F1 to front using fragment manager. Same for all other fragment

So far i tried this for every fragment in my container (FRAGMENT ACTIVITY)

if (fragmentManager.findFragmentByTag("apps")==null) {
FragmentManager fragmentManager = getSupportFragmentManager();
FragmentTransaction transaction = fragmentManager.beginTransaction();
transaction.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_FADE);

Fragment newFragment = new CategoriesFragment();
transaction.replace(R.id.content_frame, newFragment, "apps");
transaction.addToBackStack("apps");
transaction.commit();   
} else{

}

If part ensures me NO fragment is recreated (If its created already) again, but what should i write in else part so that already created fragment can be brought to front in View Hierarchy

Please Help, i'm stuck at this for 2 days.

Answer 1

I would put this code in activity class, that must have FrameLayout with id R.id.fragment_container.

private Fragment1 F1;
private Fragment2 F2;
private Fragment3 F3;
private Fragment4 F4;       

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    F1 = new Fragment1();
    getSupportFragmentManager().beginTransaction().add(R.id.fragment_container, F1).commit();
    F2 = new Fragment2();
    getSupportFragmentManager().beginTransaction().add(R.id.fragment_container, F2).commit();
    F3 = new Fragment3();
    getSupportFragmentManager().beginTransaction().add(R.id.fragment_container, F3).commit();
    F4 = new Fragment4();
    getSupportFragmentManager().beginTransaction().add(R.id.fragment_container, F4).commit();

    //if needed show F1
    getSupportFragmentManager().beginTransaction().show(F1).commit();

}

And add this for button click:

public void onBtnClick(View view){
    if(mShowF1){
        getSupportFragmentManager().beginTransaction().show(F1).commit();
        getSupportFragmentManager().beginTransaction().hide(F2).commit();
        getSupportFragmentManager().beginTransaction().hide(F3).commit();
        getSupportFragmentManager().beginTransaction().hide(F4).commit();
    }
    //...
}

On button click(s) you can show, that fragment that you want and hide others.

NOTE (@developer1011): For use after activity save state call commitAllowingStateLoss (). Use with care, because fragment is not restored with activity restoration.

NOTE: MainActivity should implement OnFragmentInteractionListener for each Fragment.

public class MainActivity extends FragmentActivity implements Fragment1.OnFragmentInteractionListener, Fragment2.OnFragmentInteractionListener, Fragment3.OnFragmentInteractionListener, Fragment4.OnFragmentInteractionListener {//..

    @Override
    public void onFragmentInteraction(Uri uri) {
        //
    }
}