Question

我试图在按下时更改凸起按钮的颜色，一段时间以来我一直遇到问题，我现在整个按钮小部件的代码是

children: <Widget>[
                  Expanded(
                    child: Container(
                      child: new SizedBox(
                        width: 15,
                        height: 60,
                        child: new RaisedButton(
                            color: pressed ? Color(0xFF1D1E33) : Colors.blue,
                            hoverColor: Colors.blueAccent,
                            focusColor: Colors.blueAccent,
                            child: Text(
                              'Male',
                              style: TextStyle(
                                  fontSize: 26,
                                  fontWeight: FontWeight.bold,
                                  color: Colors.white),
                              textAlign: TextAlign.center,
                            ),
                            onPressed: () => setState((){pressed = !pressed;})),
                      ),

我也有一个如下所示的布尔值，但是运行代码“断言失败：布尔表达式不能为空”时收到错误消息

bool get pressed => null;

set pressed(bool pressed) {}

Answer 1

您可以在下面复制粘贴运行完整代码
代码段

  bool _pressed = false;

  bool get pressed {
    return _pressed;
  }

  set pressed(bool pressed) {
    _pressed = pressed;
  }

工作演示

完整代码

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

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

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;
  bool _pressed = false;

  bool get pressed {
    return _pressed;
  }

  set pressed(bool pressed) {
    _pressed = pressed;
  }

  void _incrementCounter() {
    setState(() {
      _counter++;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Container(
                child: new SizedBox(
                    width: 100,
                    height: 60,
                    child: new RaisedButton(
                        color: pressed ? Color(0xFF1D1E33) : Colors.blue,
                        hoverColor: Colors.blueAccent,
                        focusColor: Colors.blueAccent,
                        child: Text(
                          'Male',
                          style: TextStyle(
                              fontSize: 26,
                              fontWeight: FontWeight.bold,
                              color: Colors.white),
                          textAlign: TextAlign.center,
                        ),
                        onPressed: () => setState(() {
                              pressed = !pressed;
                            })))),
            Text(
              'You have pushed the button this many times:',
            ),
            Text(
              '$_counter',
              style: Theme.of(context).textTheme.display1,
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ),
    );
  }
}

我如何更改凸起按钮onPressed的颜色？

1 个答案: