android - 在Flutter中将数据从一页传递到另一页

Question

我知道有很多这样的问题，但是我对Flutter还是陌生的，我还没有找到适合我需要的帖子，或者我只是在想错了。

我基本上有settings.dart和home.dart。现在，我想基于米_isMetresChecked或英尺_isFeetChecked的复选框值，在主屏幕上更改单位，但不要立即切换到主屏幕，允许用户继续配置设置(最终还有更多内容要添加)，然后当他们返回主屏幕时，它就会更新。我尝试使用SettingsData类作为合并所有配置，然后通过Navigator传递它的一种方法，但是尽管我没有成功，但不允许我允许用户停留在“设置”页面上。

那么，如何在 View 之间传递数据而又不切换 View ？

home.dart

import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';

import 'applicationbar.dart';
import 'navigationdrawer.dart';
import 'bluetooth.dart';


class LuggageFollowerMain extends StatefulWidget {
  @override
  _LuggageFollowerMainState createState() => _LuggageFollowerMainState();
}

class _LuggageFollowerMainState extends State<LuggageFollowerMain> {
  String _string = '0m';  //so if _isFeetChecked is true in settings.dart this is '0ft'


  @override
  Widget build(BuildContext context) {

    return Scaffold(
      backgroundColor: Colors.grey[900],
      appBar: ApplicationBar(title: 'Luggage Follower'),
      drawer: NavigationDrawer(),
      body:Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children: <Widget>[
          Padding(
            padding: const EdgeInsets.symmetric(vertical: 10,horizontal: 0),
            child: Text('Luggage Status', style: Theme.of(context).textTheme.body2),
          ),
          Padding(
            padding: const EdgeInsets.symmetric(vertical: 10,horizontal: 0),
            child: Text('Paired', style: Theme.of(context).textTheme.body1),
          ),
          Padding(
            padding: const EdgeInsets.symmetric(vertical: 20,horizontal: 0),
            child: Divider(height: 3.0, color: Colors.pinkAccent, indent: 150, endIndent: 150),
          ),
          Padding(
            padding: const EdgeInsets.symmetric(vertical: 10,horizontal: 0),
            child: Text('Distance to Luggage', style: Theme.of(context).textTheme.body2),
          ),
          Padding(
            padding: const EdgeInsets.symmetric(vertical: 10,horizontal: 0),
            child: Text(_string, style: Theme.of(context).textTheme.body1), //dynamic text here
          ),
          Padding(
            padding: const EdgeInsets.symmetric(vertical: 10,horizontal: 0),
            child: LuggageFollow(),
          ),
        ],
      ),
    );
  }
}

settings.dart

import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:audioplayers/audio_cache.dart';

import 'applicationbar.dart';
import 'navigationdrawer.dart';

class SettingsData {
  bool feet;
  bool metres;

  SettingsData({this.feet, this.metres});
}

class Settings extends StatefulWidget {
  @override
  _SettingsState createState() => _SettingsState();
}

class _SettingsState extends State<Settings> {
  static bool _isFeetChecked   = false;
  static bool _isMetersChecked = true;


  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: ApplicationBar(title: 'Settings'),
      drawer: NavigationDrawer(),
      body: Column(
          //crossAxisAlignment: CrossAxisAlignment.start,
          children: <Widget>[
            Padding(
              padding: EdgeInsets.symmetric(vertical: 20.0,horizontal: 20),
              child: Text('Distance Units')
            ),
            Divider(
              height: 3.0,
              color: Colors.pink,
            ),
            Padding(
              padding: EdgeInsets.symmetric(vertical: 20.0,horizontal: 0),
              child: CheckboxListTile(
                title: Text('Distance in feet', style: Theme.of(context).textTheme.body1),
                value: _isFeetChecked,
                onChanged: (bool value) {
                  setState(() {
                    _isFeetChecked = value; _isMetersChecked = !value;});
                },
                checkColor: Colors.white,
                activeColor: Colors.pink,
                subtitle: Text('1 foot ~ 0.3 metres',style: Theme.of(context).textTheme.display2),
              ),
            ),
            Padding(
              padding: EdgeInsets.symmetric(vertical: 20.0,horizontal: 0),
              child: CheckboxListTile(
                title: Text('Distance in metres', style: Theme.of(context).textTheme.body1),
                value: _isMetersChecked,
                onChanged: (bool value) {
                  setState(() { _isMetersChecked = value; _isFeetChecked = !value;updateData();});
                },
                checkColor: Colors.white,
                activeColor: Colors.pink,
                subtitle: Text('1 metre ~ 3 feet',style: Theme.of(context).textTheme.display2),
              ),
            ),
            Padding(
              padding: EdgeInsets.symmetric(vertical: 30.0,horizontal: 20),
              child: Text('Notifications')
            ),
            Divider(
                height: 3.0,
                color: Colors.pink,
            ),

              ),
            ),
          ],
      ),
    );
  }
}

Answer 1

因此，首先您只需要1 bool即可进行测量。它是英尺还是米。这样可以简化事情。这是一个使用回调函数在父窗口小部件中设置状态更改的示例。这只是许多可以完成的方式中的一种，可能还有其他您可能更喜欢的方式。

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(
        primarySwatch: Colors.blue,
      ),
      home: LuggageFollowerMain(),
    );
  }
}


class Settings extends StatefulWidget {

  //Static references to our parent widget varibles
  final bool isM;
  final changeMeeters;

  Settings(bool isM, changeMeeters(bool meeters)):
  this.isM = isM,
  this.changeMeeters = changeMeeters
  ;

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

class _SettingsState extends State<Settings> {
  @override
  void initState() { 
    super.initState();
    //set our varible state to be that of the parent screen
    //isMeeters is a local var to Settings and is changeable. 
    //isM is a static and can't be changed. isM was passed in 
    //from our home screen. We need a changeable var or the 
    //checkboxes won't update correctly. Thats why we need 
    //isMeeters (lol bad spelling). When the settings screen 
    //first loads we use initState to take the value of 
    //isM(from our home screen) and copy it into isMeeters 
    //as it's initial value before it is built and shown 
    //to the user for the first time. 
    isMeeters = widget.isM;
  }

  //our varible to use for our check boxes
  var isMeeters;
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(),
      body: Column(
        children: <Widget>[
          Padding(
              padding: EdgeInsets.symmetric(vertical: 20.0, horizontal: 20),
              child: Text('Distance Units')),
          Divider(
            height: 3.0,
            color: Colors.pink,
          ),
          Padding(
            padding: EdgeInsets.symmetric(vertical: 20.0, horizontal: 0),
            child: CheckboxListTile(
              title: Text('Distance in feet',
                  style: Theme.of(context).textTheme.body1),
              //use the local var change when tapped
              value: isMeeters,
              onChanged: (bool value) {
                setState(() {
                  isMeeters = true;
                });
                //call back to the parent widget so it can be updated
                widget.changeMeeters(true);
              },
              checkColor: Colors.white,
              activeColor: Colors.pink,
              subtitle: Text('1 foot ~ 0.3 metres',
                  style: Theme.of(context).textTheme.display2),
            ),
          ),
          Padding(
            padding: EdgeInsets.symmetric(vertical: 20.0, horizontal: 0),
            child: CheckboxListTile(
              title: Text('Distance in metres',
                  style: Theme.of(context).textTheme.body1),
              //use the local var change when tapped. Use ! to invert the bool. This way only one is needed.
              value: !isMeeters,
              onChanged: (bool value) {
                setState(() {
                  isMeeters = false;
                });
                //call back to the parent widget so it can be updated
                widget.changeMeeters(false);
              },
              checkColor: Colors.white,
              activeColor: Colors.pink,
              subtitle: Text('1 metre ~ 3 feet',
                  style: Theme.of(context).textTheme.display2),
            ),
          ),
          Padding(
              padding: EdgeInsets.symmetric(vertical: 30.0, horizontal: 20),
              child: Text('Notifications')),
          Divider(
            height: 3.0,
            color: Colors.pink,
          ),
        ],
      ),
    );
  }
}

class LuggageFollowerMain extends StatefulWidget {
  @override
  _LuggageFollowerMainState createState() => _LuggageFollowerMainState();
}

class _LuggageFollowerMainState extends State<LuggageFollowerMain> {
      //store the distance as a number not a string
      double distance = 0.0;
      //store the measurement type setting
      bool isMeeters = false;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(),
      floatingActionButton: FloatingActionButton(
        onPressed: () {
          Navigator.push(
            context,
            MaterialPageRoute(builder: (context) => Settings(isMeeters, (newMeeters){
              //when we get our callback from settings we set the change to the home screen var here
              setState(() {
                isMeeters = newMeeters;
              });

            })),
          );
        },
      ),
      backgroundColor: Colors.grey[900],
      body: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children: <Widget>[
          Padding(
            padding: const EdgeInsets.symmetric(vertical: 10, horizontal: 0),
            child: Text('Luggage Status',
                style: Theme.of(context).textTheme.body2),
          ),
          Padding(
            padding: const EdgeInsets.symmetric(vertical: 10, horizontal: 0),
            child: Text('Paired', style: Theme.of(context).textTheme.body1),
          ),
          Padding(
            padding: const EdgeInsets.symmetric(vertical: 20, horizontal: 0),
            child: Divider(
                height: 3.0,
                color: Colors.pinkAccent,
                indent: 150,
                endIndent: 150),
          ),
          Padding(
            padding: const EdgeInsets.symmetric(vertical: 10, horizontal: 0),
            child: Text('Distance to Luggage',
                style: Theme.of(context).textTheme.body2),
          ),
          Padding(
            padding: const EdgeInsets.symmetric(vertical: 10, horizontal: 0),
            //use the new number var and change it's suffix m or f depending on what our setting is.
            child: Text(distance.toString() + (isMeeters ? "m" : "f"),
                style: Theme.of(context).textTheme.body1), //dynamic text here
          ),
          Padding(
            padding: const EdgeInsets.symmetric(vertical: 10, horizontal: 0),
          ),
        ],
      ),
    );
  }
}