底部导航栏的Oncreate视图存在问题

Question

这就是我要开始的。所选项目应为主页（中间）

我在OnCreate下有这个

        btmNav = findViewById(R.id.btmnav);
            btmNav.setOnNavigationItemSelectedListener((navListner));
            getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container,new RecViewFragment()).commit();

而这个外部Oncreate

private BottomNavigationView.OnNavigationItemSelectedListener navListner = new BottomNavigationView.OnNavigationItemSelectedListener() {
            @Override
            public boolean onNavigationItemSelected(@NonNull MenuItem item) {
            switch (item.getItemId()){
            case R.id.navprofile:
            getSupportFragmentManager().beginTransaction().
            replace(R.id.fragment_container,new Fragment2()).commit();
            break;
            case R.id.navmap:
            Intent intent = new Intent(MainActivityBuses.this, MapActivity.class);
            startActivity(intent);
            break;
            case R.id.navhome:
            getSupportFragmentManager().beginTransaction().
            replace(R.id.fragment_container,new Fragment2()).commit();
            break;
            case R.id.navmybus:
            getSupportFragmentManager().beginTransaction().
            replace(R.id.fragment_container,new Fragment3()).commit();
            break;
            case R.id.navinfo:
            getSupportFragmentManager().beginTransaction().
            replace(R.id.fragment_container,new Fragment4()).commit();
            break;
            }
            return true;
            }

Answer 1

我得到了答案，只需要加上这个

btmNav.getMenu().findItem(R.id.navhome).setChecked(true);

在此下方

btmNav = findViewById(R.id.btmnav);
        btmNav.setOnNavigationItemSelectedListener((navListner));
        getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container,new RecViewFragment()).commit();