handleStartBackGesture method

bool handleStartBackGesture(
  1. PredictiveBackEvent backEvent

Called at the start of a predictive back gesture.

Observers are notified in registration order until one returns true or all observers have been notified. If an observer returns true then that observer, and only that observer, will be notified of subsequent events in this same gesture (for example handleUpdateBackGestureProgress, etc.).

Observers are expected to return true if they were able to handle the notification, for example by starting a predictive back animation, and false otherwise. PredictiveBackPageTransitionsBuilder uses this mechanism to listen for predictive back gestures.

If all observers indicate they are not handling this back gesture by returning false, then a navigation pop will result when handleCommitBackGesture is called, as in a non-predictive system back gesture.

Currently, this is only used on Android devices that support the predictive back feature.


bool handleStartBackGesture(PredictiveBackEvent backEvent) => false;