Android - Back button in the title bar

Question

In many apps (Calendar, Drive, Play Store) when you tap a button and enter a new activity, the icon in the title bar turns into a back button, but for the app I am making, i

Answer 1

All you need to do in 2020:
(considering you want to return to the MainActivity)

protected void onCreate(Bundle savedInstanceState){
    ...
    getSupportActionBar().setDisplayHomeAsUpEnabled(true);
}

public boolean onOptionsItemSelected(MenuItem item) {
    Intent myIntent = new Intent(getApplicationContext(), MainActivity.class);
    startActivityForResult(myIntent, 0);
    return true;
}