Why is my actionbar home button active?

Question

Android

Why is my actionbar home button active? (R.id.home)
I did not register this in the activity

getSupportActionBar().setDisplayHomeAsUpEnabled(true);

Answer 1

And what about this function? Judging by the dock https://developer.android.com/reference/android/su... it allows you to change the home button into the Up button. And not for the presence of a button as such. By default, in all applications, the home button is active, IMHO. Otherwise, how will you return to HomeScreen.