In flutter, Widget is a way to declare and construct UI . If you are familiar with the Android or iOS development then you might make the immediate connection with the views (on Android) or UIViews (on iOS).
Read moreHow do you rebuild a stateful widget in Flutter?
The solution is to pass a new Key to WidgetB every time we need it to be rebuilt : WidgetA will see that WidgetB has changed and will rebuild it when setState is called. In other words, whenever a stateful widget’s Key property changes, calling setState on its parent will force a rebuild of the stateful widget.
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