focus
Finds the next view to focus when navigating from the currently focused view. Implements custom focus navigation logic to provide more intuitive keyboard navigation in PdfActivity, cycling through toolbar, tab bar, document, navigation buttons, and thumbnail bar in a logical order.
Return
The next view that should receive focus, or null if none found.
Parameters
focused
The view that currently has focus.
direction
The direction of focus movement (e.g., FOCUS_FORWARD, FOCUS_BACKWARD).