run
Run the ViewportTransition from current viewport to the target ViewportState.
The completion block must be invoked with true if the transition completes successfully. If the transition fails, invoke the completion block with false.
If the returned Cancelable is canceled, it's not necessary to invoke the completion block(but safe to do so, as it will just be ignored.
Transitions should handle the possibility that to state might fail to provide camera in a timely manner or might update the target camera multiple times during the transition(i.e. a 'moving target').
Return
a handle that can be used to cancel the current ViewportTransition
Parameters
to
The target ViewportState
completion
The listener to observe the completion state, it must be invoked on the main queue.