Moving between screens.
WHAT AN ACTIVITY LIFECYCLE INVOLVES
Creation, becoming visible, becoming active, losing focus, becoming hidden, and destruction.
WHAT TRIGGERS DESTRUCTION AND RECREATION
Rotation Language or theme changes The system reclaiming memory
WHY THAT MATTERS
Any state held only in the activity is lost.
WHAT TO DO ABOUT IT
Hold state where it survives recreation, and save anything else explicitly.
WHAT THE BACK STACK IS
The history of screens, which the back gesture moves through.
WHAT TO ENSURE
That back behaves as the user expects, from any entry point.
WHY FROM ANY ENTRY POINT
A notification or a link may open a deep screen directly, with no history behind it.
WHAT TO DO ABOUT THAT
Construct an appropriate back stack, or define where back goes.
WHAT MODERN NAVIGATION PROVIDES
Declared destinations and transitions, with argument passing and back stack handling.
WHAT TO AVOID
Deep nesting of screens Screens that cannot be reached directly Navigation that loses state
WHAT TO TEST
Entering every screen directly, then pressing back.
