When I am in Fragment 5, for example, and I press the back button, the application comes out. What I want is when I press the Back button, I open Fragment No. 1. How can i do that?
I have tried many codes but it is not working, like
FragmentManager fm = getActivity().getSupportFragmentManager();
for(int i = 0; i < fm.getBackStackEntryCount(); ++i) {
fm.popBackStack();
}
and
getSupportFragmentManager().popBackStack(null, FragmentManager.POP_BACK_STACK_INCLUSIVE);
Here is my fragment code in MainActivity
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// make new object and find the view "BottomNavigationView"
BottomNavigationView navigationView = findViewById(R.id.bottom_navigation);
// To make the first fragment shows when the app start.
// We will ignore the "activity_main" and we will make new activity(fragment) called "fragment_home"
// and we will add all views we want to display them on it.
// (fragment_layout) it is a fragment have id was defined in "activity_main"
getSupportFragmentManager().beginTransaction().replace(R.id.fragment_layout,
new HomeFragment()).commit();
// make Listener to call the fragments on buttons
// to start new fragment
navigationView.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() {
@Override
public boolean onNavigationItemSelected(@NonNull MenuItem item) {
Fragment selectedFragment = null;
switch (item.getItemId()) {
// first fragment "home"
case R.id.home_item:
selectedFragment = new HomeFragment();
break;
// second fragment "videos"
case R.id.videos_item:
selectedFragment = new VideosFragment();
break;
// third fragment "ebadat"
case R.id.ebadat_item:
selectedFragment = new EbadatFragment();
break;
// fourth fragment "images"
case R.id.images_item:
selectedFragment = new ImagesFragment();
break;
// fifth fragment "more"
case R.id.settings_item:
selectedFragment = new MoreFragment();
break;
}
assert selectedFragment != null;
getSupportFragmentManager().beginTransaction().replace(R.id.fragment_layout, selectedFragment).commit();
return true;
}
});
}
Add the onBackPressed Method:
@Override
public void onBackPressed() {
//super.onBackPressed(); delete this line
// and start your fragment:
NextFragment nextFrag= new NextFragment();
getActivity().getSupportFragmentManager().beginTransaction()
.replace(R.id.Layout_container, nextFrag, "findThisFragment")
.addToBackStack(null)
.commit();
}
First you have to implement the onBackPressed Method in your Fragment.
create an interface with the name IOnBackPressed: click package -> new Java Class -> and choose interface in Kind -> OK your interface should look like this:
public interface IOnBackPressed { boolean onBackPressed(); }
after that you open your MainActivity and add this:
@Override public void onBackPressed() { //super.onBackPressed(); delete this line // and start your fragment: Fragment fragment = getSupportFragmentManager().findFragmentById(R.id.fragment_container); if (.(fragment instanceof IOnBackPressed) ||.((IOnBackPressed) fragment);onBackPressed()) { super.onBackPressed(); } }
you implement this to your Fragment:
public class Profil_Fragment extends Fragment implements IOnBackPressed
and add this to the Fragment:
@Override public boolean onBackPressed() { //do what you want NextFragment nextFrag= new NextFragment(); getActivity().getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container, nextFrag, "findThisFragment").addToBackStack(null).commit(); return true; }
Add backstack and tag (you can use fragment name like "HomeFragment") for replacing fragment.
replace(fragmentId, fragment, fragmentName).addToBackStack(fragmentName)
And pop fragment like this
popBackStack(fragmentName,0)
Try adding transaction.addToBackStack(tag);
For example:
FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
ft.replace(R.id.fragment_layout, selectedFragment);
ft.addToBackStack( "tag" ).commit();
That will add your fragments to the backstack so the back button can work appropriately.
The technical post webpages of this site follow the CC BY-SA 4.0 protocol. If you need to reprint, please indicate the site URL or the original address.Any question please contact:yoyou2525@163.com.