按后退按钮移动到上一个片段时显示空白屏幕

Question

when I'm pressing the back button it is moving to the previous fragment but also displaying a blank screen and I need to click it to eliminate it. How do I get rid of this blank screen? I saw its somehow connected to the first addToBackStack but I still couldn't fix it

here's my onNavigationItemSelected method:

public boolean onNavigationItemSelected(@NonNull MenuItem menuItem) {
        Fragment fragment=null;
        switch (menuItem.getItemId()) {
            case R.id.nav_home:
                fragment=new HomeFragment();
                break;
            case R.id.nav_income:
                fragment=new IncomeFragment();
                break;
            case R.id.nav_expense:
                fragment=new ExpenseFragment();
                break;
            case R.id.nav_sign_out:
                FirebaseAuth mAuth = FirebaseAuth.getInstance();
                mAuth.signOut();
                startActivity(new Intent(getApplicationContext(), WelcomeActivity.class));
                Toast.makeText(getApplicationContext(), "Signed Out", Toast.LENGTH_LONG).show();
                break;

        }
        if(fragment!=null)
            getSupportFragmentManager().beginTransaction().
                    replace(R.id.fragment_container, fragment).addToBackStack("").commit();

        return true;
    }

here's my onBackPressed() method:

  public void onBackPressed() {
        final FragmentManager fragmentManager = getSupportFragmentManager();
        if (drawerLayout.isDrawerOpen(GravityCompat.START)) {
            drawerLayout.closeDrawer(GravityCompat.START);
        } else {
            AlertDialog.Builder builder = new AlertDialog.Builder(this, R.style.AlertDialogCustom);
            if (fragmentManager.getBackStackEntryCount() == 0) {
                builder.setTitle("Sign out");
                builder.setMessage("Are you sure you want to sign out?");
                builder.setPositiveButton("YES", new DialogInterface.OnClickListener() {

                    public void onClick(DialogInterface dialog, int which) {
                        firebaseAuth.signOut();
                        dialog.dismiss();
                        startActivity(new Intent(getApplicationContext(), WelcomeActivity.class));
                    }
                });

                builder.setNegativeButton("NO", new DialogInterface.OnClickListener() {

                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        dialog.dismiss();
                    }
                });
            } else {
                    fragmentManager.popBackStack();
            }

            AlertDialog alert = builder.create();
            alert.show();
        }
    }

Answer 1

You need to change if condition as per below

if(fragmentManager.getBackStackEntryCount() - 1 == 0){
    //Do your code
}else{
    fragmentManager.popBackStack();
}

As per your code please find below full code

public void onBackPressed() {
    final FragmentManager fragmentManager = getSupportFragmentManager();
    if (drawerLayout.isDrawerOpen(GravityCompat.START)) {
        drawerLayout.closeDrawer(GravityCompat.START);
    } else {
        if (fragmentManager.getBackStackEntryCount() - 1 == 0) {
            AlertDialog.Builder builder = new AlertDialog.Builder(this, R.style.AlertDialogCustom);
            builder.setTitle("Sign out");
            builder.setMessage("Are you sure you want to sign out?");
            builder.setPositiveButton("YES", new DialogInterface.OnClickListener() {
                public void onClick(DialogInterface dialog, int which) {
                    firebaseAuth.signOut();
                    dialog.dismiss();
                    startActivity(new Intent(getApplicationContext(), WelcomeActivity.class));
                }
            });
            builder.setNegativeButton("NO", new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialog, int which) {
                    dialog.dismiss();
                }
            });
            AlertDialog alert = builder.create();
            alert.show();
        } else {
            fragmentManager.popBackStack();
        }
    }
}

I hope this can help You!

Thank You.

Answer 2

Update onCreateView of your all fragment

View view; 
public View onCreateView(LayoutInflater inflater, ViewGroup container,
    Bundle savedInstanceState) {
    if (view != null) {
    if (view.getParent() != null) {
        ((ViewGroup)view.getParent()).removeView(view);
    }
    return view;
}

View v=inflater.inflate(R.layout.tests, container, false);

Hope this will helps!!

Answer 3

Hi I guess It is because last fragment is getting removed and you are seeing blank screen which is fragment container where you add fragments. So, when last screen is reached please finish that activity before starting other one. Use This code for starting new Activity.

Intent intent=new Intent(getApplicationContext(), WelcomeActivity.class);
finish();   //finish used to finish blank screen activity
startActivity(intent);