createState function creates a mutable state in Flutter-CodePudding

createState:

Creates the mutable state for this widget at a given location in the tree.

https://api.flutter.dev/flutter/widgets/StatefulWidget/createState.html

Now, in code:

class A extends StatefulWidget {

  @override
  _AState createState() => _AState();
}

class _AState extends State<A> {
}

Here we create a separate class named _AState which inherits from a predefined class named State?

So, what is createState' role here? How does it create a mutable state for us?

CodePudding user response：

In order to create a stateful widget in a flutter, it uses the createState() method. Stateful Widget means a widget that has a mutable state.

CodePudding user response：

With createState you tell the StatefulWidget which class to use as state for this widget. And you tell it here that it needs to create an instance of _AState for this widget.

By the way, it is also recommended to write it as

State<A> createState() => _AState();

It still works the way you wrote it but the IDE might complain about

Avoid using private types in public APIs

Saying the return type is State<A> instead of _AState removes this warning.