You just need to add a field to child widget then in parent widget change value of that field and call setState() .
Read moreDoes setState rebuild?
setState() It is used to notify the framework that “data has changed”, and the widget at this build context should be rebuilt .
Read moreHow do I make widgets not rebuild in flutter?
The ultimate solution to prevent widget rebuild by flutter
Read moreHow do I rebuild a child’s widget?
A nice way to rebuild only a child widget when a value in the parent changes is to use ValueNotifier and ValueListenableBuilder . Add an instance of ValueNotifier to the parent’s state class, and wrap the widget you want to rebuild in a ValueListenableBuilder .
Read moreDoes setState rebuild widget?
When setState() is called on a State, all descendent widgets rebuild . Therefore, localize the setState() call to the part of the subtree whose UI actually needs to change.
Read moreDoes setState rebuild the entire widget tree?
If you call setState() on WidgetB it’ll rebuild itself and it’s descendants, no matter if they are Stateless or Stateful Widgets.
Read moreHow do you rebuild the parent widget in Flutter?
How can I force the parent to rebuild? Since your parent is a Stateless Widget, you cannot change it’s color. You must use a StatefulWidget instead. Otherwise, you can use a Callback function from the child to the parent .
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