如何从一个 class 屏幕获取值到另一个 class 屏幕并在 flutter 中填充这些值？

How to get values from one class screen to another class and populate those values in flutter?

我有一个主 class 和 TimePickerScreen class，我正在尝试从 TimePickerScreen[=29= 获取值] class 到 Main class 来填充这些值，我包装了 From 和 To 文本与 GestureDetector 调用 TimePickerScreen class 在 bottomSheet 内和 selecting 时间和点击保存按钮值之后应该填充 select Time 但我不知道如何获取这些值，下面我粘贴了我的代码和屏幕截图，任何人都可以帮助我，在此先感谢. 主要Class

import 'package:flutter/material.dart';
import 'package:single_selection_horizontal/timedatepicker_screen.dart';

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

class MyApp extends StatelessWidget {

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: "custom time picker horizontal",
      home: SelectTimeDate(),
    );
  }
}

class SelectTimeDate extends StatefulWidget {

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

class _SelectTimeDateState extends State<SelectTimeDate> {
  String pfromTime ='';
  String ptoTime ='';
  //String fromDate='';
  //String toDate='';
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('custom time picker horizontal'),
      ),
      body: Center(
        child: Container(
          child: Column(
            crossAxisAlignment: CrossAxisAlignment.center,
            mainAxisAlignment: MainAxisAlignment.center,
            children: [
              GestureDetector(
                onTap: pickerBottomSheet,
                child: Container(
                  child: Column(
                    children: [
                      Text(" From ",style: TextStyle(fontSize: 20,color: Colors.black),),
                      Text(
                        pfromTime==''
                        ? "Select Time"
                        : "$pfromTime",style: TextStyle(fontSize: 15,color: Colors.grey),),
                    ],
                  ),
                ),
              ),
              SizedBox(height: 10,),
              GestureDetector(
                onTap: pickerBottomSheet,
                child: Container(
                  child: Column(
                    children: [
                      Text(" To ",style: TextStyle(fontSize: 20,color: Colors.black),),
                      Text(
                        ptoTime==''
                        ? "Select Time"
                        : "$ptoTime",style: TextStyle(fontSize: 15,color: Colors.grey),),
                    ],
                  ),
                ),
              ),
            ],
          ),
        ),
      ),
    );
  }

  pickerBottomSheet(){
    showModalBottomSheet(
        context: context,
        isScrollControlled: true,
        isDismissible: true,
        builder: (BuildContext context){
          return TimePickerScreen();
        }
        );
  }
}

TimePickerScreen

import 'package:flutter/material.dart';

class TimePickerScreen extends StatefulWidget {

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

class _TimePickerScreenState extends State<TimePickerScreen> {
  String selectedFromTime = " ";
  List<String> fromTimeList = ["0:00", "0:30", "1:00", "1:30", "2:00", "2:30", "3:00", "3:30", "4:00", "4:30", "5:00", "5:30", "6:00", "6:30"];
  List<bool> fromTimeListSelect =[false,false,false,false,false,false,false,false,false,false,false,false,false,false,];

  String selectedToTime =" ";
  List<String> toTimeList = ["0:00", "0:30", "1:00", "1:30", "2:00", "2:30", "3:00", "3:30", "4:00", "4:30", "5:00", "5:30", "6:00", "6:30"];
  List<bool> toTimeListSelect =[false,false,false,false,false,false,false,false,false,false,false,false,false,false,];

  @override
  Widget build(BuildContext context) {
    return Container(
      height: MediaQuery.of(context).size.height * 0.80,
      decoration: BoxDecoration(
        borderRadius: BorderRadius.only(
          topLeft: Radius.circular(10),
          topRight: Radius.circular(10),
        )
      ),
      child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            
            Container(
              padding: EdgeInsets.fromLTRB(50, 50, 50, 50),
                child: Text("Time Picker",style: TextStyle(fontSize: 40,color: Colors.purple),)),
            Divider(),
            Text("Select From Time",style: TextStyle(fontSize: 20,color: Colors.purple),),
            fromTime(),
            Divider(),
            Text("Select To Time",style: TextStyle(fontSize: 20,color: Colors.purple),),
            toTime(),
            FlatButton(onPressed: (){

            },
                color: Colors.purple,
                padding: EdgeInsets.fromLTRB(15, 15, 15, 15),
                child: Text("Save",style: TextStyle(fontSize: 20,color: Colors.white),)),
            SizedBox(height: 100,),
            Text('From : $selectedFromTime To : $selectedToTime'),

          ],
        ),
    );

  }
  Widget fromTime(){
    return Expanded(
      child: ListView.builder(
        shrinkWrap: true,
        scrollDirection: Axis.horizontal,
        itemCount: fromTimeList.length,
        itemBuilder: (BuildContext context,int index){
          return GestureDetector(
            child: Container(
              padding: EdgeInsets.all(6),
              child: Center(
                  child: Text(fromTimeList[index],
                    style: TextStyle(color: fromTimeListSelect[index] ? Colors.white : Colors.black ,fontSize: 16),)),
              decoration: BoxDecoration(
                shape: BoxShape.circle,
                color: fromTimeListSelect[index] ? Colors.purple : Colors.white,
              ),
            ),
            onTap: (){
              setState(() {
                for(int i=0; i< fromTimeListSelect.length; i++){
                  fromTimeListSelect[i] = false;
                }
                fromTimeListSelect[index] = !fromTimeListSelect[index];
                fromTimeListSelect[index] == true ? selectedFromTime =fromTimeList[index] : selectedFromTime= ' ';
                print(fromTimeListSelect[index]);
                print(fromTimeList[index]);
              });
            },
          );

        },),
    );
  }

  Widget toTime(){
    return Expanded(
      child: ListView.builder(
        shrinkWrap: true,
        scrollDirection: Axis.horizontal,
        itemCount: fromTimeList.length,
        itemBuilder: (BuildContext context,int index){
          return GestureDetector(
            child: Container(
              padding: EdgeInsets.all(6),
              child: Center(
                  child: Text(toTimeList[index],
                    style: TextStyle(color: toTimeListSelect[index] ? Colors.white : Colors.black ,fontSize: 16),)),
              decoration: BoxDecoration(
                shape: BoxShape.circle,
                color: toTimeListSelect[index] ? Colors.purple : Colors.white,
              ),
            ),
            onTap: (){
              setState(() {
                for(int i=0; i< toTimeListSelect.length;i++) {
                  toTimeListSelect[i] = false;
                }
                toTimeListSelect[index] = !toTimeListSelect[index];
                toTimeListSelect[index] == true ? selectedToTime =toTimeList[index] : selectedToTime= ' ';
                print(toTimeListSelect[index]);
                print(toTimeList[index]);
              });
            },
          );

        },),
    );
  }
}

您可以定义一个 class 来从底部对结果建模 sheet :

class TimeSelectResult{
  final String pFromTime;
  final String pToTime;

  TimeSelectResult(this.pFromTime, this.pToTime);
}

然后在底部的代码sheet中，当用户选择2次from和to时，你调用Navigator.of(context).pop(timeSelectResult)，其中timeSelectResult是你的[=14]的一个变量=] 填充了用户选择的结果。

所以你现在这样称呼底部 sheet:

 pickerBottomSheet() async {
    final TimeSelectResult? result = await showModalBottomSheet(
        context: context,
        isScrollControlled: true,
        isDismissible: true,
        builder: (BuildContext context) {
          return TimePickerScreen();
        });

    if (result != null) {
      setState(() {
        pfromTime = result.pFromTime;
        ptoTime = result.pToTime;
      });
    }
  }

在 class 级别添加一个回调方法 TimePickerScreen，例如 

 final Function callback;

并像

一样在Save button上使用它 
      onPressed: () {
                widget.callback(selectedFromTime, selectedToTime); //here
                Navigator.of(context).pop();
              },

并像

一样使用TimePickerScreen 
  return TimePickerScreen(
            callback: (String from, String to) {
              print("From $from TO $to");
             setState(() {
                pfromTime = from;
                ptoTime = to;
              });
            },
          );

making nullable String will be better choice in this, becasue its depend on user.

完整代码

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: "custom time picker horizontal",
      home: SelectTimeDate(),
    );
  }
}

class SelectTimeDate extends StatefulWidget {
  @override
  _SelectTimeDateState createState() => _SelectTimeDateState();
}

class _SelectTimeDateState extends State<SelectTimeDate> {
  String pfromTime = '';
  String ptoTime = '';
  //String fromDate='';
  //String toDate='';
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('custom time picker horizontal'),
      ),
      body: Center(
        child: Container(
          child: Column(
            crossAxisAlignment: CrossAxisAlignment.center,
            mainAxisAlignment: MainAxisAlignment.center,
            children: [
              GestureDetector(
                onTap: pickerBottomSheet,
                child: Container(
                  child: Column(
                    children: [
                      Text(
                        " From ",
                        style: TextStyle(fontSize: 20, color: Colors.black),
                      ),
                      Text(
                        pfromTime == '' ? "Select Time" : pfromTime,
                        style: TextStyle(fontSize: 15, color: Colors.grey),
                      ),
                    ],
                  ),
                ),
              ),
              SizedBox(
                height: 10,
              ),
              GestureDetector(
                onTap: pickerBottomSheet,
                child: Container(
                  child: Column(
                    children: [
                      Text(
                        " To ",
                        style: TextStyle(fontSize: 20, color: Colors.black),
                      ),
                      Text(
                        ptoTime == '' ? "Select Time" : ptoTime,
                        style: TextStyle(fontSize: 15, color: Colors.grey),
                      ),
                    ],
                  ),
                ),
              ),
            ],
          ),
        ),
      ),
    );
  }

  pickerBottomSheet() {
    showModalBottomSheet(
        context: context,
        isScrollControlled: true,
        isDismissible: true,
        builder: (BuildContext context) {
          return TimePickerScreen(
            callback: (String from, String to) {
              print("From $from TO $to");
            },
          );
        });
  }
}

class TimePickerScreen extends StatefulWidget {
  final Function callback;

  const TimePickerScreen({Key? key, required this.callback}) : super(key: key);

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

class _TimePickerScreenState extends State<TimePickerScreen> {
  String selectedFromTime = " ";
  List<String> fromTimeList = [
    "0:00",
    "0:30",
    "1:00",
    "1:30",
    "2:00",
    "2:30",
    "3:00",
    "3:30",
    "4:00",
    "4:30",
    "5:00",
    "5:30",
    "6:00",
    "6:30"
  ];
  List<bool> fromTimeListSelect = [
    false,
    false,
    false,
    false,
    false,
    false,
    false,
    false,
    false,
    false,
    false,
    false,
    false,
    false,
  ];

  String selectedToTime = " ";
  List<String> toTimeList = [
    "0:00",
    "0:30",
    "1:00",
    "1:30",
    "2:00",
    "2:30",
    "3:00",
    "3:30",
    "4:00",
    "4:30",
    "5:00",
    "5:30",
    "6:00",
    "6:30"
  ];
  List<bool> toTimeListSelect = [
    false,
    false,
    false,
    false,
    false,
    false,
    false,
    false,
    false,
    false,
    false,
    false,
    false,
    false,
  ];

  @override
  Widget build(BuildContext context) {
    return Container(
      height: MediaQuery.of(context).size.height * 0.80,
      decoration: const BoxDecoration(
          borderRadius: BorderRadius.only(
        topLeft: Radius.circular(10),
        topRight: Radius.circular(10),
      )),
      child: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children: [
          Container(
              padding: EdgeInsets.fromLTRB(50, 50, 50, 50),
              child: Text(
                "Time Picker",
                style: TextStyle(fontSize: 40, color: Colors.purple),
              )),
          Divider(),
          Text(
            "Select From Time",
            style: TextStyle(fontSize: 20, color: Colors.purple),
          ),
          fromTime(),
          Divider(),
          Text(
            "Select To Time",
            style: TextStyle(fontSize: 20, color: Colors.purple),
          ),
          toTime(),
          FlatButton(
              onPressed: () {
                widget.callback(selectedFromTime, selectedToTime); //here
                Navigator.of(context).pop();
              },
              color: Colors.purple,
              padding: EdgeInsets.fromLTRB(15, 15, 15, 15),
              child: Text(
                "Save",
                style: TextStyle(fontSize: 20, color: Colors.white),
              )),
          SizedBox(
            height: 100,
          ),
          Text('From : $selectedFromTime To : $selectedToTime'),
        ],
      ),
    );
  }

  Widget fromTime() {
    return Expanded(
      child: ListView.builder(
        shrinkWrap: true,
        scrollDirection: Axis.horizontal,
        itemCount: fromTimeList.length,
        itemBuilder: (BuildContext context, int index) {
          return GestureDetector(
            child: Container(
              padding: EdgeInsets.all(6),
              child: Center(
                  child: Text(
                fromTimeList[index],
                style: TextStyle(
                    color:
                        fromTimeListSelect[index] ? Colors.white : Colors.black,
                    fontSize: 16),
              )),
              decoration: BoxDecoration(
                shape: BoxShape.circle,
                color: fromTimeListSelect[index] ? Colors.purple : Colors.white,
              ),
            ),
            onTap: () {
              setState(() {
                for (int i = 0; i < fromTimeListSelect.length; i++) {
                  fromTimeListSelect[i] = false;
                }
                fromTimeListSelect[index] = !fromTimeListSelect[index];
                fromTimeListSelect[index] == true
                    ? selectedFromTime = fromTimeList[index]
                    : selectedFromTime = ' ';
                print(fromTimeListSelect[index]);
                print(fromTimeList[index]);
              });
            },
          );
        },
      ),
    );
  }

  Widget toTime() {
    return Expanded(
      child: ListView.builder(
        shrinkWrap: true,
        scrollDirection: Axis.horizontal,
        itemCount: fromTimeList.length,
        itemBuilder: (BuildContext context, int index) {
          return GestureDetector(
            child: Container(
              padding: EdgeInsets.all(6),
              child: Center(
                  child: Text(
                toTimeList[index],
                style: TextStyle(
                    color:
                        toTimeListSelect[index] ? Colors.white : Colors.black,
                    fontSize: 16),
              )),
              decoration: BoxDecoration(
                shape: BoxShape.circle,
                color: toTimeListSelect[index] ? Colors.purple : Colors.white,
              ),
            ),
            onTap: () {
              setState(() {
                for (int i = 0; i < toTimeListSelect.length; i++) {
                  toTimeListSelect[i] = false;
                }
                toTimeListSelect[index] = !toTimeListSelect[index];
                toTimeListSelect[index] == true
                    ? selectedToTime = toTimeList[index]
                    : selectedToTime = ' ';
                print(toTimeListSelect[index]);
                print(toTimeList[index]);
              });
            },
          );
        },
      ),
    );
  }
}