在按钮上的文本字段小部件中显示输出 在 Flutter 中单击按钮计算后单击按钮

Question

我有三个不同的小部件（文本字段），我需要一个来输入，另外两个在单击按钮后显示计算结果。在这种情况下，一个文本字段以开尔文为单位显示温度，另外两个以华氏温度和摄氏度显示结果。如果 Celcius 文本字段接受输入，则两个显示转换后的结果。请原谅我的代码可能很脏，但我是绿色的。每当在任一文本字段中完成输入时，我都会显示结果。

void main() {
  runApp(TemperatureCalculator());
}

class TemperatureCalculator extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Temperature Calculator',
      theme: ThemeData(
        primaryColor: Colors.cyanAccent,
      ),
      home: new TemperatureHome(),
    );
  }
}

class TemperatureHome extends StatefulWidget {
  @override
  createState() => TemperatureState();
}

class TemperatureState extends State<TemperatureHome> {
  String result = '';
  final temperatureMeasurer = ['Celcius', 'Kelvin', 'Farenheit'];
  double formBorders = 6.0;
  TextEditingController celciusController = TextEditingController();
  TextEditingController farenheitController = TextEditingController();
  TextEditingController kelvinController = TextEditingController();

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text("Temperature Converter"),
        backgroundColor: Colors.deepOrange,
      ),
      body: Column(children: <Widget>[
        Padding(
            padding: EdgeInsets.only(top: formBorders, bottom: formBorders),
            child: TextField(
              controller: celciusController,
              decoration: InputDecoration(
                  labelText: 'Temperature in Degrees Celcius',
                  hintText: 'e.g 25',
                  border: OutlineInputBorder(
                      borderRadius: BorderRadius.circular(5.0))),
              keyboardType: TextInputType.number,
            )),
        Padding(
            padding: EdgeInsets.only(top: formBorders, bottom: formBorders),
            child: TextField(
              controller: farenheitController,
              decoration: InputDecoration(
                  labelText: 'Temperature in FarenHeit',
                  hintText: 'e.g 25',
                  border: OutlineInputBorder(
                      borderRadius: BorderRadius.circular(5.0))),
              keyboardType: TextInputType.number,
            )),
        Padding(
          padding: EdgeInsets.only(top: formBorders, bottom: formBorders),
          child: TextField(
            controller: kelvinController,
            decoration: InputDecoration(
                labelText: 'Temperature in Kelvin',
                hintText: 'e.g 25',
                border: OutlineInputBorder(
                    borderRadius: BorderRadius.circular(5.0))),
            keyboardType: TextInputType.number,
          ),
        ),
        Row(
          children: <Widget>[
            RaisedButton(
              color: Theme.of(context).buttonColor,
              textColor: Theme.of(context).primaryColorDark,
              onPressed: () {
              setState(() {
                
              });
                  
              },
              child: Text(
                'Convert',
                textScaleFactor: 1.5,
              ),
            ),
            RaisedButton(
                color: Theme.of(context).buttonColor,
                textColor: Theme.of(context).primaryColorDark,
                child: Text(
                  'Reset',
                  textScaleFactor: 1.5,
                ),
                onPressed: () {
                  setState(() {
                    reset();
                  });
                }),
          ],
        ),
      ]),
    );
  }

  double converter() {
    double celciusTemp = double.parse(celciusController.text);
    double farenheitTemp = double.parse(farenheitController.text);
    double kelvinTemp = double.parse(kelvinController.text);

    double farenheitToCelsius = (farenheitTemp - 32) * 5 / 9;
    double farenheitToKelvin = (farenheitTemp - 32) * 5 / 9 + 273.15;
    double celciusToFarenheit = (celciusTemp * 9 / 5) + 32;
    double celsiusToKelvin = celciusTemp + 273.15;
    double kelvinToFarenheit = (kelvinTemp - 273.15) * 9 / 5 + 32;
    double kelvinToCelcius = kelvinTemp - 273.15;

    //if()
  }

  void reset() {
    celciusController.text = '';
    farenheitController.text = '';
    kelvinController.text = '';
    setState(() {
      result = '';
    });
  }
}
`

Answer 1

此解决方案可行，但您肯定需要一些代码更改，例如在转换器方法中处理 null 情况。

void main() {
  runApp(TemperatureCalculator());
}

class TemperatureCalculator extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Temperature Calculator',
      theme: ThemeData(
        primaryColor: Colors.cyanAccent,
      ),
      home: new TemperatureHome(),
    );
  }
}

class TemperatureHome extends StatefulWidget {
  @override
  createState() => TemperatureState();
}

class TemperatureState extends State<TemperatureHome> {
  String result = '';
  final temperatureMeasurer = ['Celcius', 'Kelvin', 'Farenheit'];
  double formBorders = 6.0;
  TextEditingController celciusController = TextEditingController();
  TextEditingController farenheitController = TextEditingController();
  TextEditingController kelvinController = TextEditingController();

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text("Temperature Converter"),
        backgroundColor: Colors.deepOrange,
      ),
      body: Column(children: <Widget>[
        Padding(
            padding: EdgeInsets.only(top: formBorders, bottom: formBorders),
            child: TextField(
              controller: celciusController,
              decoration: InputDecoration(
                  labelText: 'Temperature in Degrees Celcius',
                  hintText: 'e.g 25',
                  border: OutlineInputBorder(
                      borderRadius: BorderRadius.circular(5.0))),
              keyboardType: TextInputType.number,
            )),
        Padding(
            padding: EdgeInsets.only(top: formBorders, bottom: formBorders),
            child: TextField(
              controller: farenheitController,
              decoration: InputDecoration(
                  labelText: 'Temperature in FarenHeit',
                  hintText: 'e.g 25',
                  border: OutlineInputBorder(
                      borderRadius: BorderRadius.circular(5.0))),
              keyboardType: TextInputType.number,
            )),
        Padding(
          padding: EdgeInsets.only(top: formBorders, bottom: formBorders),
          child: TextField(
            controller: kelvinController,
            decoration: InputDecoration(
                labelText: 'Temperature in Kelvin',
                hintText: 'e.g 25',
                border: OutlineInputBorder(
                    borderRadius: BorderRadius.circular(5.0))),
            keyboardType: TextInputType.number,
          ),
        ),
        Row(
          children: <Widget>[
            RaisedButton(
              color: Theme.of(context).buttonColor,
              textColor: Theme.of(context).primaryColorDark,
              onPressed: () {
                setState((){
                  converter();    
                });
              
                  
              },
              child: Text(
                'Convert',
                textScaleFactor: 1.5,
              ),
            ),
            RaisedButton(
                color: Theme.of(context).buttonColor,
                textColor: Theme.of(context).primaryColorDark,
                child: Text(
                  'Reset',
                  textScaleFactor: 1.5,
                ),
                onPressed: () {
                  setState(() {
                    reset();
                  });
                }),
          ],
        ),
      ]),
    );
  }

  void converter() {
    double celciusTemp = double.tryParse(celciusController.text);
    double farenheitTemp = double.tryParse(farenheitController.text);
    double kelvinTemp = double.tryParse(kelvinController.text);

    double farenheitToCelsius = ((farenheitTemp ?? 0) - 32) * 5 / 9;
    double farenheitToKelvin = ((farenheitTemp ?? 0) - 32) * 5 / 9 + 273.15;
    double celciusToFarenheit = ((celciusTemp ?? 0) * 9 / 5) + 32;
    double celsiusToKelvin = (celciusTemp ?? 0) + 273.15;
    double kelvinToFarenheit = ((kelvinTemp ?? 0) - 273.15) * 9 / 5 + 32;
    double kelvinToCelcius = (kelvinTemp ?? 0) - 273.15;
    
    if(celciusController.text.isNotEmpty 
       && double.tryParse(celciusController.text) != null){
     
        farenheitController.text = celciusToFarenheit.toString();
        kelvinController.text = celsiusToKelvin.toString();
      
    }else if(farenheitController.text.isNotEmpty 
       && double.tryParse(farenheitController.text) != null){
      celciusController.text = farenheitToCelsius.toString();
      kelvinController.text = farenheitToKelvin.toString();
    }else if(kelvinController.text.isNotEmpty 
       && double.tryParse(kelvinController.text) != null){
      celciusController.text = kelvinToCelcius.toString();
      farenheitController.text = kelvinToFarenheit.toString();
    }

    //if()
  }

  void reset() {
    celciusController.text = '';
    farenheitController.text = '';
    kelvinController.text = '';
    setState(() {
      result = '';
    });
  }
}

Answer 2

这行得通吗：

if (celciusController.text != null && celciusController.text.length > 0) {
  farenheitController.text = (int.parse(celciusController.text)* 9 / 5) + 32;
  kelvinController.text = int.parse(celciusController.text)+ 273.15;
} 
else if (farenheitController.text != null && farenheitController.text.length > 0) {
  celciusController.text = (int.parse(farenheitController.text)- 32) * 5 / 9;
  kelvinController.text = (int.parse(farenheitController.text)- 32) * 5 / 9 + 273.15;
}
else{
  ....
}

这行得通吗？

Answer 3

您可以在 initState() 中将侦听器添加到文本控制器。解决方法的一个简单示例如下所示：

  @override
  void dispose() {        
    celciusController.dispose();
    farenheitController.dispose();
    kelvinController.dispose();
    super.dispose();
  }

  @override
  void initState() {
    celciusController.addListener((){
        
        setState(() {
                  converter();
                });
    });
    farenheitController.addListener((){
        
        setState(() {
                  converter();
                });
    });
    kelvinController.addListener((){
        
        setState(() {
                  converter();
                });
    });

    super.initState();
  }

阅读更多来自official document。