Question

我已经尝试了以下有关Radio类的教程，但是当我单击按钮时按钮并没有改变颜色。我知道设备正在读取点击次数，因为每当单击按钮但按钮颜色没有改变时，我都会显示一条打印语句以显示。

我只是不知道问题是什么

int radioValue = -1;

void _handleRadioValueChanged (int value){
  setState(() {
    radioValue = value;
    print(radioValue);
  });
}

return new Scaffold(
      body: new Center(
        child: new Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            new Radio<int>(
                activeColor: Colors.green,
                value: 0,
                groupValue: radioValue,
                onChanged: _handleRadioValueChanged),

        new Radio<int>(
            activeColor: Colors.green,
            value: 1,
            groupValue: radioValue,
            onChanged: _handleRadioValueChanged),

        new Radio <int>(
            activeColor: Colors.green,
            value: 2,
            groupValue: radioValue,
            onChanged: _handleRadioValueChanged),

    ),
  )
);

我希望按钮在被按下时会发生变化，但只是保持在值= -1的状态； </ p>

Answer 1

下面是代码：

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: HomePage(),
    );
  }
}

class HomePage extends StatefulWidget {
  @override
  _HomePageState createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  int radioValue = -1;

  void _handleRadioValueChanged(int value) {
    setState(() {
      radioValue = value;
      print(radioValue);
    });
  }

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
        body: new Center(
      child: new Column(mainAxisAlignment: MainAxisAlignment.center, children: [
        new Radio(
            activeColor: Colors.green,
            value: 0,
            groupValue: radioValue,
            onChanged: _handleRadioValueChanged),
        new Radio<int>(
            activeColor: Colors.green,
            value: 1,
            groupValue: radioValue,
            onChanged: _handleRadioValueChanged),
        new Radio<int>(
            activeColor: Colors.green,
            value: 2,
            groupValue: radioValue,
            onChanged: _handleRadioValueChanged),
      ]),
    ));
  }
}

Desired Output

单击时Flutter单选按钮不更改值/也不更改活动颜色

1 个答案: