How is application orientation (landscape or portrait) locked?

Question

I have tried to freeze orientation using:

setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);

Although the display stays in

Answer 1

A more specific example of the activity section of the AndroidManifest.xml for portrait orientation:

Where android:screenOrientation sets the initial orientation and android:configChanges voids the events that triggers the corresponding lifecycle methods on screen changes.