我想问一下，如何将滑块的值扔到文本字段中，文本字段的输入值可以调整滑块中的值？

Question

This the Image. 我想问一下，如何将滑块的值扔到文本字段中，文本字段的输入值可以调整滑块中的值？使值相等且彼此同步。在文本字段中输入的输入可以与滑块中的值相同，并且滑块值可以出现在文本字段中。

                                                                        Container(
                                                                        width: 130,
                                                                        child: TextField(
                                                                        style: new TextStyle(color: Colors.white),
                                                                        controller: max,
                                                                        decoration: InputDecoration(
                                                                          labelText: 'Max',
                                                                          labelStyle: TextStyle(color: Colors.white),
                                                                          hintStyle: TextStyle(color: Colors.white),

                                                                        ),
                                                                      ),
                                                                      ),
                                                                      // new Text(values.start.toInt().toString()),
                                                                      // new Text(values.end.toInt().toString()),
                                                                      new Container(
                                                                        padding: EdgeInsets.only(top: 50.0),
                                                                        child: new RangeSlider(
                                                                          min: 1,
                                                                          max: 100,
                                                                          divisions: 100,
                                                                          values: values,
                                                                          labels: labels,
                                                                          onChanged: (value) {
                                                                            modalSetState(() {

                                                                              print('START: ${value.start}, END: ${value.end}');
                                                                              setValuesSlider(value);
                                                                              labels = RangeLabels('${values.start.toInt().toString()}', '${values.end.toInt().toString()}');
                                                                            }); //create custom setState for this state
                                                                          },
                                                                        ),
                                                                      ),
                                                                    ]);
                                                              }
                                                            }),
                                                      ],
                                                    ),

Answer 1

当文本更改更新范围滑块的开始或结束值时，使用TextField Contorller的侦听器。

startController.addListener(_setStartValue);

完整代码

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        // This is the theme of your application.
        //
        // Try running your application with "flutter run". You'll see the
        // application has a blue toolbar. Then, without quitting the app, try
        // changing the primarySwatch below to Colors.green and then invoke
        // "hot reload" (press "r" in the console where you ran "flutter run",
        // or simply save your changes to "hot reload" in a Flutter IDE).
        // Notice that the counter didn't reset back to zero; the application
        // is not restarted.
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

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

  // This widget is the home page of your application. It is stateful, meaning
  // that it has a State object (defined below) that contains fields that affect
  // how it looks.

  // This class is the configuration for the state. It holds the values (in this
  // case the title) provided by the parent (in this case the App widget) and
  // used by the build method of the State. Fields in a Widget subclass are
  // always marked "final".

  final String title;

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

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;
  double _starValue = 10;
  double _endValue = 80;
  double minValue = 0.0;
  double maxValue = 100.0;

  final startController = TextEditingController();
  final endController = TextEditingController();

  void _incrementCounter() {
    setState(() {
      // This call to setState tells the Flutter framework that something has
      // changed in this State, which causes it to rerun the build method below
      // so that the display can reflect the updated values. If we changed
      // _counter without calling setState(), then the build method would not be
      // called again, and so nothing would appear to happen.
      _counter++;
    });
  }

  @override
  void initState() {
    super.initState();

    startController.addListener(_setStartValue);
    endController.addListener(_setEndValue);
  }

  @override
  void dispose() {
    // Clean up the controller when the widget is removed from the widget tree.
    // This also removes the _printLatestValue listener.
    startController.dispose();
    endController.dispose();
    super.dispose();
  }

  _setStartValue() {
    if (double.parse(startController.text).roundToDouble() <=
            double.parse(endController.text).roundToDouble() &&
        double.parse(startController.text).roundToDouble() >= minValue &&
        double.parse(endController.text).roundToDouble() >= minValue &&
        double.parse(startController.text).roundToDouble() <= maxValue &&
        double.parse(endController.text).roundToDouble() <= maxValue) {
      setState(() {
        _starValue = double.parse(startController.text).roundToDouble();
      });
    }
    print("Second text field: ${startController.text}");
  }

  _setEndValue() {
    if (double.parse(startController.text).roundToDouble() <=
        double.parse(endController.text).roundToDouble() &&
        double.parse(startController.text).roundToDouble() >= minValue &&
        double.parse(endController.text).roundToDouble() >= minValue &&
        double.parse(startController.text).roundToDouble() <= maxValue &&
        double.parse(endController.text).roundToDouble() <= maxValue) {
      setState(() {
        _endValue = double.parse(endController.text).roundToDouble();
      });
    }
    print("Second text field: ${endController.text}");
  }

  @override
  Widget build(BuildContext context) {
    // This method is rerun every time setState is called, for instance as done
    // by the _incrementCounter method above.
    //
    // The Flutter framework has been optimized to make rerunning build methods
    // fast, so that you can just rebuild anything that needs updating rather
    // than having to individually change instances of widgets.
    return Scaffold(
      appBar: AppBar(
        // Here we take the value from the MyHomePage object that was created by
        // the App.build method, and use it to set our appbar title.
        title: Text(widget.title),
      ),
      body: Center(
        // Center is a layout widget. It takes a single child and positions it
        // in the middle of the parent.
        child: Column(
          // Column is also a layout widget. It takes a list of children and
          // arranges them vertically. By default, it sizes itself to fit its
          // children horizontally, and tries to be as tall as its parent.
          //
          // Invoke "debug painting" (press "p" in the console, choose the
          // "Toggle Debug Paint" action from the Flutter Inspector in Android
          // Studio, or the "Toggle Debug Paint" command in Visual Studio Code)
          // to see the wireframe for each widget.
          //
          // Column has various properties to control how it sizes itself and
          // how it positions its children. Here we use mainAxisAlignment to
          // center the children vertically; the main axis here is the vertical
          // axis because Columns are vertical (the cross axis would be
          // horizontal).
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            TextField(
              decoration: InputDecoration(
                  border: InputBorder.none, hintText: 'Enter  start value'),
              controller: startController,
            ),
            TextField(
              decoration: InputDecoration(
                  border: InputBorder.none, hintText: 'Enter end value'),
              controller: endController,
            ),
            RangeSlider(
              values: RangeValues(_starValue, _endValue),
              min: minValue,
              max: maxValue,
              onChanged: (values) {
                setState(() {
                  _starValue = values.start.roundToDouble();
                  _endValue = values.end.roundToDouble();
                  startController.text =
                      values.start.roundToDouble().toString();
                  endController.text = values.end.roundToDouble().toString();
                });
              },
            ),
            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),
      ), // This trailing comma makes auto-formatting nicer for build methods.
    );
  }
}