Switch between Fragments with onNavigationItemSelected in new Navigation Drawer Activity template (Android Studio 1.4 onward)

Question

IntelliJ has made changes to the Navigation Drawer template Activity in Android Studio with fewer lines of code in the Activity class. The new Activity class looks like this

Answer 1

I used a template auto-created by Android Studio 1.4 too, and I had encounter same difficulties as you.

First, I changed activity_main.xml

A DrawerLayout that contains two parts:

1. Main Screen (LinearLayout)
2. the Drawer (NavigationView)

Main Screen contains the ActionBar and the FrameLayout (R.id.content) will be replaced by a fragment. The Drawer contains the header and the menu.

So, we now override onNavigationItemSelected and replace R.id.content with a fragment.

Here is my MainActivity code:

    @Override
public boolean onNavigationItemSelected(MenuItem item) {
    Fragment fragment;
    FragmentTransaction ft = getFragmentManager().beginTransaction();
    // Handle navigation view item clicks here.
    int id = item.getItemId();

    if (id == R.id.nav_A) {
        fragment = new AFragment();
        ft.replace(R.id.content, fragment).commit();        
    } else if (id == R.id.nav_B){
        fragment = new BFragment();
        ft.replace(R.id.content, fragment).commit();
    } else if (id == R.id.nav_settings) {
        Intent intent = new Intent(MainActivity.this, SettingsActivity.class);
        startActivity(intent);
    }

    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    drawer.closeDrawer(GravityCompat.START);
    return true;
}

Main page is also a fragment. And I set up main page in onCreate method although I am not sure if there is a better way to set up main page.

//MainPageFragment
    FragmentTransaction ft = getFragmentManager().beginTransaction();
    ft.replace(R.id.content, new MainPageFragment()).commit();

PS. here is the toolbar.xml, the ActionBar