Dismissible constructor
Creates a widget that can be dismissed.
The key
argument must not be null because Dismissibles are commonly
used in lists and removed from the list when dismissed. Without keys, the
default behavior is to sync widgets based on their index in the list,
which means the item after the dismissed item would be synced with the
state of the dismissed item. Using keys causes the widgets to sync
according to their keys and avoids this pitfall.
Implementation
const Dismissible({
@required Key key,
@required this.child,
this.background,
this.secondaryBackground,
this.onResize,
this.onDismissed,
this.direction = DismissDirection.horizontal,
this.resizeDuration = const Duration(milliseconds: 300),
this.dismissThresholds = const <DismissDirection, double>{},
this.movementDuration = const Duration(milliseconds: 200),
this.crossAxisEndOffset = 0.0,
}) : assert(key != null),
assert(secondaryBackground != null ? background != null : true),
super(key: key);