Flutter：TextButton 中的 setState 不起作用

Question

Dice image not changing on onPress
setState not setting dice image for random number

child: Image.asset('images/dice$leftDiceNumber.png'), not working but
child: Image.asset('images/dice2.png'), is working that means hard code is working

var leftDiceNumber = 3; getting only dice3.png as i initialize it for leftDiceNumber

Please help for getting random image when onPress

---

No errors in App

class DicePage extends StatefulWidget { const DicePage({Key? key}): super(key: key); @override _DicePageState createState() => _DicePageState(); } class _DicePageState extends State<DicePage> { @override Widget build(BuildContext context) { var leftDiceNumber = 3; return Center( child: Row( children: [ Expanded( child: TextButton( onPressed: () { setState(() { leftDiceNumber = Random().nextInt(6) + 1; print(leftDiceNumber); // getting value in console }); }, child: Image.asset('images/dice$leftDiceNumber.png'), //child: Image.asset('images/dice1.png'), // ( works ) ),),], ),);}}

Answer 1

That is because every time you call setState() it calls the build method, and you have defined leftDiceNumber = 3 inside the build method. So even though the setState() changes the value it again gets set to 3.

Solution: Move var leftDiceNumber = 3; outside the build method.

class _DicePageState extends State<DicePage> {
  var leftDiceNumber = 3;
  
@override
  Widget build(BuildContext context) {
    return YourWidget();
  }
}