Question

我正在尝试构建骰子游戏，如果用户单击该图像，应该从资产文件夹中更改该图像，但是该图像没有更改，但是终端中的值正在更新setState方法可能无法正常工作

Declare @Product Table(ProductId INT, Code DECIMAL(10,2))

INSERT INTO @Product(ProductId, Code)
Select 844558,3
UNION
Select 844558,3.5
UNION
Select 844558,4
UNION
Select 296013,2
UNION
Select 296013,3
UNION
Select 494948,3.5
UNION
Select 494948,4
UNION
Select 494948,9
UNION
Select 392991,4
UNION
Select 392991,9.5 


SELECT ProductId
FROM @Product
WHERE ProductID not in (select ProductID from @product where Code=9)
GROUP BY ProductId
HAVING MIN(Code) >= 3;

它应该显示更新的图像

Answer 1

您需要将变量移至build方法之外。它们会在每个版本上重置。

import 'package:flutter/material.dart';

import 'dart:math';

void main() {
  return runApp(
    MaterialApp(
      home: Scaffold(
        backgroundColor: Colors.red,
        appBar: AppBar(
          title: Center(child: Text('Dicee')),
          backgroundColor: Colors.red,
        ),
        body: DicePage(),
      ),
    ),
  );
}
class DicePage extends StatefulWidget {
  @override
  _DicePageState createState() => _DicePageState();
}

class _DicePageState extends State<DicePage> {
  int leftDiceNumber = 5;
  int rightDiceNumber = 2;

  @override
  Widget build(BuildContext context) {
    return Center(
      child: Row(
        children: <Widget>[
          Expanded(
            child: FlatButton(
              onPressed: (){
                setState(() {
                  leftDiceNumber = Random().nextInt(6) + 1;
                  print('$leftDiceNumber');
                });
              },
              child: Image.asset('images/dice$leftDiceNumber.png'),
            ),
          ),
          Expanded(
            child: FlatButton(
              onPressed: (){
                setState(() {
                  rightDiceNumber = Random().nextInt(6) + 1;
                  print('$rightDiceNumber');
                });
              },
              child: Image.asset('images/dice$rightDiceNumber.png'),
            ),
          ),
        ],
      ),
    );
  }
}

setState函数不会在statefull小部件下更新图像

1 个答案: