androidandroid-fragmentsbottomnavigationviewfragment-oncreateview

Android - PageView in new BottomNavigationBar - prevent reload fragments


In my StartActivity the BottomNavigationBar Listener has the following setup:

private GuideFragment guideFragment = new GuideFragment();
private MapFragment mapFragment = new MapFragment();
private MoreFragment moreFragment = new MoreFragment();

private BottomNavigationView.OnNavigationItemSelectedListener mOnNavigationItemSelectedListener
        = new BottomNavigationView.OnNavigationItemSelectedListener() {

    @Override
    public boolean onNavigationItemSelected(@NonNull MenuItem item) {
        Fragment selectedFragment = null;
        switch (item.getItemId()) {
            case R.id.navigation_guide:
                selectedFragment = guideFragment;
                break;
            case R.id.navigation_map:
                selectedFragment = mapFragment;
                break;
            case R.id.navigation_more:
                selectedFragment = moreFragment;
                break;
        }
        FragmentTransaction transaction = getFragmentManager().beginTransaction();
        transaction.replace(R.id.content, selectedFragment);
        transaction.commit();
        return true;
    }

};

As I mentioned above I want to prevent that the selected fragments always reloads the sources/view. I tried out some stuff like - in the fragments:

if (rootView == null)
     inflater.inflate...

But the fragments still recreate the view and load (in my case) webresources new.

I read something that a PageView could help, especially

offScreenPageLimit

should do the magic.

My main question is where should I implement a PageViewer - Is it possible in my StartActivity? Or can I solve the problem in an other way?


Solution

  • I did it boys! There is no ViewPager necessary.

    Here is my solution (all coded in StartActivity not in Fragments):

    private final GuideFragment guideFragment = new GuideFragment();
    private final MapFragment mapFragment = new MapFragment();
    private final MoreFragment moreFragment = new MoreFragment();
    private final android.app.FragmentManager fm = getFragmentManager();
    Fragment active = guideFragment;
    
    private BottomNavigationView.OnNavigationItemSelectedListener mOnNavigationItemSelectedListener
            = new BottomNavigationView.OnNavigationItemSelectedListener() {
    
        @Override
        public boolean onNavigationItemSelected(@NonNull MenuItem item) {
            switch (item.getItemId()) {
                case R.id.navigation_guide:
                    if(active != guideFragment) {
                        fm.beginTransaction().show(guideFragment).commit();
                    }
                    else {
                        fm.beginTransaction().hide(active).show(guideFragment).commit();
                    }
                    active = guideFragment;
                    break;
                case R.id.navigation_map:
                    fm.beginTransaction().hide(active).show(mapFragment).commit();
                    active = mapFragment;
                    break;
                case R.id.navigation_more:
                    fm.beginTransaction().hide(active).show(moreFragment).commit();
                    active = moreFragment;
                    break;
            }
    
            return true;
        }
    
    };
    

    and in onCreate list the transaction commits.

    fm.beginTransaction().add(R.id.content,moreFragment).commit();
    fm.beginTransaction().add(R.id.content, mapFragment).commit();
    fm.beginTransaction().add(R.id.content, guideFragment).commit();
    

    It is very important to commit the first tabs fragment last(fragm3,fragm2,fragm1) if you have 3 tabs.

    Highly speed performance on the smartphone now by not loading every fragment new/refresh.