A method assigned to IconButton (onPressed) is called automatically on state initialisation-CodePudding

I try to show an overlapping widget which is being added to a stack when the appropriate button is pressed. Here is simplified example of the code:

...

class _MyApp extends State<MyApp> {
    bool _isFloatingWidgetShown = false;

    @override
    Widget build(BuildContext context) {

        void _showFloatingWidget() {
            setState(() {
                _isFloatingWidgetShown = true;
            });
        }

        void _hideFloatingWidget() {
            setState(() {
                _isFloatingWidgetShown = false;
            });
        }

        return MaterialApp(
            home: Scaffold(
                body: Container(
                    child: Stack(
                        children: [
                            ...
                            if (_isFloatingWidgetShown) MyFloatingWidget(onClose: _hideFloatingWidget)
                            ]
                            ...

class MyFloatingWidget extends StatefulWidget {
  const MyFloatingWidget(
      {Key? key, required this.onClose})
      : super(key: key);

  final Function onClose;
  ...

class _MyFloatingWidget extends State<MyFloatingWidget> {
@override
Widget build(BuildContext context) {
   return IconButton(
                   onPressed: widget.onClose(),
                   icon: Icon(
                       Icons.close))
                   ...

But once the widget is shown it immediately calls _hideFloatingWidget method and I get the following error: FlutterError (setState() or markNeedsBuild() called during build...

Why does it call assigned to onPressed method by itself during state initialization?

CodePudding user response：

You should not use (if not necessary) functions in build method. When you do this, do not use setState in it. Just _showFloatingWidget and _hideFloatingWidget use out of the build method. "build" method is calling whenever you show the screen or when you use "setState". It calls the function because of it.

    @override
Widget build(BuildContext context) {
    return MaterialApp(
        home: Scaffold(
            body: Container(
                child: Stack(
                    children: [
                        ...
                        if (_isFloatingWidgetShown) MyFloatingWidget(onClose: _hideFloatingWidget)
                        ]
                        ...
} 

void _showFloatingWidget() {
    setState(() {
        _isFloatingWidgetShown = true;
    });
}

void _hideFloatingWidget() {
    setState(() {
        _isFloatingWidgetShown = false;
    });
}

CodePudding user response：

The solution is to use the following method notation for onPressed property of IconButton:

...
onPressed: () {
     widget.onClose();
}
...