问题
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?
回答1:
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.
来源：https://stackoverflow.com/questions/44375904/android-pageview-in-new-bottomnavigationbar-prevent-reload-fragments