Unhandled Exception Bad state: Stream has already been listened to

Listener class Null safety . A widget that calls callbacks in response to common pointer events . It listens to events that can construct gestures, such as when the pointer is pressed, moved, then released or canceled.

Listener class Null safety . A widget that calls callbacks in response to common pointer events . It listens to events that can construct gestures, such as when the pointer is pressed, moved, then released or canceled.

The following example shows how listen() can be put to use:

The following example shows how listen() can be put to use: