How setState() function redraw the new state after quick changes in statefull management in Flutter

It easily redraw the new state but how this concept work? I am beginner in Flutter

CodePudding user response：

According to Flutter Documentation,

Calling setState notifies the framework that the internal state of this object has changed in a way that might impact the user interface in this subtree, which causes the framework to schedule a build for this State object.

So if you want to update the state of a widget then you need to use a setState function. Though you must have a Stateful Widget in order to use it as a widget's state can't be changed in a Stateless Widget. You can read more about it on Flutter Website

CodePudding user response：

Statefull widgets are obvious in flutter, these widgets are immutable but their states are mutable, they can change,

https://api.flutter.dev/flutter/widgets/StatefulWidget-class.html

When you finally run your APP, you create a widget tree and for that widget tree flutter creates a corresponding element tree,

So when you call setState, the flutter framework checks for changes in widget tree and and updates corresponding element tree,

****Flutter framework is so smart that without building whole element tree from the scratch, it just updates it as per changes in widget tree.

***To get more performance benefit keep the state deeper inside the widget tree so the parents remain unaffected while flutter framework update the element tree.