flutter - 如何根据屏幕大小调整 flutter 小部件的大小？

Question

我是 flutter 的初学者，我发现了这个包 https://pub.dev/packages/flutter_calendar_carousel我想使用的。我正在尝试将它用于 flutter 网络应用程序。我去运行了这个例子，它可以工作，但是当我最大化窗口时出现问题，它看起来不太好；大圆圈，与在小窗口中时看起来不一样(大小问题，缩放不好):



我尝试使用 AspectRatio 小部件，它看起来更好，但它仍然太大。我不确定如何正确使用纵横比，但还有其他方法可以解决吗？ TLDR；我希望日历可读并根据屏幕大小进行缩放。
这是示例 btw 中的代码:

import 'package:flutter_calendar_carousel/flutter_calendar_carousel.dart'
    show CalendarCarousel;
import 'package:flutter_calendar_carousel/classes/event.dart';
import 'package:flutter_calendar_carousel/classes/event_list.dart';
import 'package:intl/intl.dart' show DateFormat;

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

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      title: 'dooboolab flutter calendar',
      theme: new 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 press Run > Flutter Hot Reload in IntelliJ). Notice that the
        // counter didn't reset back to zero; the application is not restarted.
        primarySwatch: Colors.blue,
      ),
      home: new MyHomePage(title: 'Flutter Calendar Carousel Example'),
    );
  }
}

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() => new _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  DateTime _currentDate = DateTime(2019, 2, 3);
  DateTime _currentDate2 = DateTime(2019, 2, 3);
  String _currentMonth = DateFormat.yMMM().format(DateTime(2019, 2, 3));
  DateTime _targetDateTime = DateTime(2019, 2, 3);
//  List<DateTime> _markedDate = [DateTime(2018, 9, 20), DateTime(2018, 10, 11)];
  static Widget _eventIcon = new Container(
    decoration: new BoxDecoration(
        color: Colors.white,
        borderRadius: BorderRadius.all(Radius.circular(1000)),
        border: Border.all(color: Colors.blue, width: 2.0)),
    child: new Icon(
      Icons.person,
      color: Colors.amber,
    ),
  );

  EventList<Event> _markedDateMap = new EventList<Event>(
    events: {
      new DateTime(2019, 2, 10): [
        new Event(
          date: new DateTime(2019, 2, 10),
          title: 'Event 1',
          icon: _eventIcon,
          dot: Container(
            margin: EdgeInsets.symmetric(horizontal: 1.0),
            color: Colors.red,
            height: 5.0,
            width: 5.0,
          ),
        ),
        new Event(
          date: new DateTime(2019, 2, 10),
          title: 'Event 2',
          icon: _eventIcon,
        ),
        new Event(
          date: new DateTime(2019, 2, 10),
          title: 'Event 3',
          icon: _eventIcon,
        ),
      ],
    },
  );

  CalendarCarousel _calendarCarousel, _calendarCarouselNoHeader;

  @override
  void initState() {
    /// Add more events to _markedDateMap EventList
    _markedDateMap.add(
        new DateTime(2019, 2, 25),
        new Event(
          date: new DateTime(2019, 2, 25),
          title: 'Event 5',
          icon: _eventIcon,
        ));

    _markedDateMap.add(
        new DateTime(2019, 2, 10),
        new Event(
          date: new DateTime(2019, 2, 10),
          title: 'Event 4',
          icon: _eventIcon,
        ));

    _markedDateMap.addAll(new DateTime(2019, 2, 11), [
      new Event(
        date: new DateTime(2019, 2, 11),
        title: 'Event 1',
        icon: _eventIcon,
      ),
      new Event(
        date: new DateTime(2019, 2, 11),
        title: 'Event 2',
        icon: _eventIcon,
      ),
      new Event(
        date: new DateTime(2019, 2, 11),
        title: 'Event 3',
        icon: _eventIcon,
      ),
    ]);
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    /// Example with custom icon
    _calendarCarousel = CalendarCarousel<Event>(
      onDayPressed: (DateTime date, List<Event> events) {
        this.setState(() => _currentDate = date);
        events.forEach((event) => print(event.title));
      },
      weekendTextStyle: TextStyle(
        color: Colors.red,
      ),
      thisMonthDayBorderColor: Colors.grey,
//          weekDays: null, /// for pass null when you do not want to render weekDays
      headerText: 'Custom Header',
      weekFormat: true,
      markedDatesMap: _markedDateMap,
      height: 200.0,
      selectedDateTime: _currentDate2,
      showIconBehindDayText: true,
//          daysHaveCircularBorder: false, /// null for not rendering any border, true for circular border, false for rectangular border
      customGridViewPhysics: NeverScrollableScrollPhysics(),
      markedDateShowIcon: true,
      markedDateIconMaxShown: 2,
      selectedDayTextStyle: TextStyle(
        color: Colors.yellow,
      ),
      todayTextStyle: TextStyle(
        color: Colors.blue,
      ),
      markedDateIconBuilder: (event) {
        return event.icon;
      },
      minSelectedDate: _currentDate.subtract(Duration(days: 360)),
      maxSelectedDate: _currentDate.add(Duration(days: 360)),
      todayButtonColor: Colors.transparent,
      todayBorderColor: Colors.green,
      markedDateMoreShowTotal:
          true, // null for not showing hidden events indicator
//          markedDateIconMargin: 9,
//          markedDateIconOffset: 3,
    );

    /// Example Calendar Carousel without header and custom prev & next button
    _calendarCarouselNoHeader = CalendarCarousel<Event>(
      todayBorderColor: Colors.green,
      onDayPressed: (DateTime date, List<Event> events) {
        this.setState(() => _currentDate2 = date);
        events.forEach((event) => print(event.title));
      },
      daysHaveCircularBorder: true,
      showOnlyCurrentMonthDate: false,
      weekendTextStyle: TextStyle(
        color: Colors.red,
      ),
      thisMonthDayBorderColor: Colors.grey,
      weekFormat: false,
//      firstDayOfWeek: 4,
      markedDatesMap: _markedDateMap,
      height: 420.0,
      selectedDateTime: _currentDate2,
      targetDateTime: _targetDateTime,
      customGridViewPhysics: NeverScrollableScrollPhysics(),
      markedDateCustomShapeBorder: CircleBorder(
        side: BorderSide(color: Colors.yellow)
      ),
      markedDateCustomTextStyle: TextStyle(
        fontSize: 18,
        color: Colors.blue,
      ),
      showHeader: false,
      todayTextStyle: TextStyle(
        color: Colors.blue,
      ),
      // markedDateShowIcon: true,
      // markedDateIconMaxShown: 2,
      // markedDateIconBuilder: (event) {
      //   return event.icon;
      // },
      // markedDateMoreShowTotal:
      //     true,
      todayButtonColor: Colors.yellow,
      selectedDayTextStyle: TextStyle(
        color: Colors.yellow,
      ),
      minSelectedDate: _currentDate.subtract(Duration(days: 360)),
      maxSelectedDate: _currentDate.add(Duration(days: 360)),
      prevDaysTextStyle: TextStyle(
        fontSize: 16,
        color: Colors.pinkAccent,
      ),
      inactiveDaysTextStyle: TextStyle(
        color: Colors.tealAccent,
        fontSize: 16,
      ),
      onCalendarChanged: (DateTime date) {
        this.setState(() {
          _targetDateTime = date;
          _currentMonth = DateFormat.yMMM().format(_targetDateTime);
        });
      },
      onDayLongPressed: (DateTime date) {
        print('long pressed date $date');
      },
    );

    return new Scaffold(
        appBar: new AppBar(
          title: new Text(widget.title),
        ),
        body: SingleChildScrollView(
          child: Column(
            crossAxisAlignment: CrossAxisAlignment.start,
            mainAxisAlignment: MainAxisAlignment.start,
            children: <Widget>[
              //custom icon
              Container(
                margin: EdgeInsets.symmetric(horizontal: 16.0),
                child: _calendarCarousel,
              ), // This trailing comma makes auto-formatting nicer for build methods.
              //custom icon without header
              Container(
                margin: EdgeInsets.only(
                  top: 30.0,
                  bottom: 16.0,
                  left: 16.0,
                  right: 16.0,
                ),
                child: new Row(
                  children: <Widget>[
                    Expanded(
                        child: Text(
                      _currentMonth,
                      style: TextStyle(
                        fontWeight: FontWeight.bold,
                        fontSize: 24.0,
                      ),
                    )),
                    FlatButton(
                      child: Text('PREV'),
                      onPressed: () {
                        setState(() {
                          _targetDateTime = DateTime(_targetDateTime.year, _targetDateTime.month -1);
                          _currentMonth = DateFormat.yMMM().format(_targetDateTime);
                        });
                      },
                    ),
                    FlatButton(
                      child: Text('NEXT'),
                      onPressed: () {
                        setState(() {
                          _targetDateTime = DateTime(_targetDateTime.year, _targetDateTime.month +1);
                          _currentMonth = DateFormat.yMMM().format(_targetDateTime);
                        });
                      },
                    )
                  ],
                ),
              ),
              Container(
                margin: EdgeInsets.symmetric(horizontal: 16.0),
                child: _calendarCarouselNoHeader,
              ), //
            ],
          ),
        ));
  }
}```

Answer 1

您可以使用 LayoutBuilder 获取父小部件的尺寸并调整子小部件的尺寸以适应。
从您的示例中，我添加了高度和宽度参数要求来创建日历轮播小部件。日历小部件上使用的高度和宽度参数来自 LayoutBuilder .

每次调整浏览器窗口大小时，Flutter 都会重建屏幕调用 Widget build() ，重建用户界面。

完整代码

import 'package:flutter/material.dart';
import 'package:flutter_calendar_carousel/flutter_calendar_carousel.dart'
    show CalendarCarousel;
import 'package:flutter_calendar_carousel/classes/event.dart';
import 'package:flutter_calendar_carousel/classes/event_list.dart';
import 'package:intl/intl.dart' show DateFormat;

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      title: 'dooboolab flutter calendar',
      theme: new ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: new MyHomePage(title: 'Flutter Calendar Carousel Example'),
    );
  }
}

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

  final String title;

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

class _MyHomePageState extends State<MyHomePage> {
  DateTime _currentDate = DateTime(2019, 2, 3);
  DateTime _currentDate2 = DateTime(2019, 2, 3);
  String _currentMonth = DateFormat.yMMM().format(DateTime(2019, 2, 3));
  DateTime _targetDateTime = DateTime(2019, 2, 3);
//  List<DateTime> _markedDate = [DateTime(2018, 9, 20), DateTime(2018, 10, 11)];
  static Widget _eventIcon = new Container(
    decoration: new BoxDecoration(
        color: Colors.white,
        borderRadius: BorderRadius.all(Radius.circular(1000)),
        border: Border.all(color: Colors.blue, width: 2.0)),
    child: new Icon(
      Icons.person,
      color: Colors.amber,
    ),
  );

  EventList<Event> _markedDateMap = new EventList<Event>(
    events: {
      new DateTime(2019, 2, 10): [
        new Event(
          date: new DateTime(2019, 2, 10),
          title: 'Event 1',
          icon: _eventIcon,
          dot: Container(
            margin: EdgeInsets.symmetric(horizontal: 1.0),
            color: Colors.red,
            height: 5.0,
            width: 5.0,
          ),
        ),
        new Event(
          date: new DateTime(2019, 2, 10),
          title: 'Event 2',
          icon: _eventIcon,
        ),
        new Event(
          date: new DateTime(2019, 2, 10),
          title: 'Event 3',
          icon: _eventIcon,
        ),
      ],
    },
  );

  // CalendarCarousel _calendarCarousel, _calendarCarouselNoHeader;

  @override
  void initState() {
    /// Add more events to _markedDateMap EventList
    _markedDateMap.add(
        new DateTime(2019, 2, 25),
        new Event(
          date: new DateTime(2019, 2, 25),
          title: 'Event 5',
          icon: _eventIcon,
        ));

    _markedDateMap.add(
        new DateTime(2019, 2, 10),
        new Event(
          date: new DateTime(2019, 2, 10),
          title: 'Event 4',
          icon: _eventIcon,
        ));

    _markedDateMap.addAll(new DateTime(2019, 2, 11), [
      new Event(
        date: new DateTime(2019, 2, 11),
        title: 'Event 1',
        icon: _eventIcon,
      ),
      new Event(
        date: new DateTime(2019, 2, 11),
        title: 'Event 2',
        icon: _eventIcon,
      ),
      new Event(
        date: new DateTime(2019, 2, 11),
        title: 'Event 3',
        icon: _eventIcon,
      ),
    ]);
    super.initState();
  }

  _calendarCarousel(double calendarHeight, double calendarWidth) {
    return CalendarCarousel<Event>(
      onDayPressed: (DateTime date, List<Event> events) {
        this.setState(() => _currentDate = date);
        events.forEach((event) => print(event.title));
      },
      weekendTextStyle: TextStyle(
        color: Colors.red,
      ),
      thisMonthDayBorderColor: Colors.grey,
//          weekDays: null, /// for pass null when you do not want to render weekDays
      headerText: 'Custom Header',
      weekFormat: true,
      markedDatesMap: _markedDateMap,
      height: calendarHeight,
      width: calendarWidth,
      selectedDateTime: _currentDate2,
      showIconBehindDayText: true,
//          daysHaveCircularBorder: false, /// null for not rendering any border, true for circular border, false for rectangular border
      customGridViewPhysics: NeverScrollableScrollPhysics(),
      markedDateShowIcon: true,
      markedDateIconMaxShown: 2,
      selectedDayTextStyle: TextStyle(
        color: Colors.yellow,
      ),
      todayTextStyle: TextStyle(
        color: Colors.blue,
      ),
      markedDateIconBuilder: (event) {
        return event.icon;
      },
      minSelectedDate: _currentDate.subtract(Duration(days: 360)),
      maxSelectedDate: _currentDate.add(Duration(days: 360)),
      todayButtonColor: Colors.transparent,
      todayBorderColor: Colors.green,
      markedDateMoreShowTotal:
          true, // null for not showing hidden events indicator
//          markedDateIconMargin: 9,
//          markedDateIconOffset: 3,
    );
  }

  _calendarCarouselNoHeader(double calendarHeight, double calendarWidth) {
    return CalendarCarousel<Event>(
      todayBorderColor: Colors.green,
      onDayPressed: (DateTime date, List<Event> events) {
        this.setState(() => _currentDate2 = date);
        events.forEach((event) => print(event.title));
      },
      daysHaveCircularBorder: true,
      showOnlyCurrentMonthDate: false,
      weekendTextStyle: TextStyle(
        color: Colors.red,
      ),
      thisMonthDayBorderColor: Colors.grey,
      weekFormat: false,
//      firstDayOfWeek: 4,
      markedDatesMap: _markedDateMap,
      height: calendarHeight,
      width: calendarWidth,
      selectedDateTime: _currentDate2,
      targetDateTime: _targetDateTime,
      customGridViewPhysics: NeverScrollableScrollPhysics(),
      markedDateCustomShapeBorder:
          CircleBorder(side: BorderSide(color: Colors.yellow)),
      markedDateCustomTextStyle: TextStyle(
        fontSize: 18,
        color: Colors.blue,
      ),
      showHeader: false,
      todayTextStyle: TextStyle(
        color: Colors.blue,
      ),
      // markedDateShowIcon: true,
      // markedDateIconMaxShown: 2,
      // markedDateIconBuilder: (event) {
      //   return event.icon;
      // },
      // markedDateMoreShowTotal:
      //     true,
      todayButtonColor: Colors.yellow,
      selectedDayTextStyle: TextStyle(
        color: Colors.yellow,
      ),
      minSelectedDate: _currentDate.subtract(Duration(days: 360)),
      maxSelectedDate: _currentDate.add(Duration(days: 360)),
      prevDaysTextStyle: TextStyle(
        fontSize: 16,
        color: Colors.pinkAccent,
      ),
      inactiveDaysTextStyle: TextStyle(
        color: Colors.tealAccent,
        fontSize: 16,
      ),
      onCalendarChanged: (DateTime date) {
        this.setState(() {
          _targetDateTime = date;
          _currentMonth = DateFormat.yMMM().format(_targetDateTime);
        });
      },
      onDayLongPressed: (DateTime date) {
        print('long pressed date $date');
      },
    );
  }

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: new AppBar(
        title: new Text(widget.title),
      ),
      body: Container(
        // use LayoutBuilder to fetch the parent widget's constraints
        child: LayoutBuilder(
          builder: (context, constraints) {
            var parentHeight = constraints.maxHeight;
            var parentWidth = constraints.maxWidth;
            debugPrint('Max height: $parentHeight, max width: $parentWidth');
            return SingleChildScrollView(
              child: Column(
                crossAxisAlignment: CrossAxisAlignment.start,
                mainAxisAlignment: MainAxisAlignment.start,
                children: <Widget>[
                  //custom icon
                  Container(
                    margin: EdgeInsets.symmetric(horizontal: 16.0),
                    // set calendar widget size percentage
                    child: _calendarCarousel(parentHeight * 0.2, parentWidth),
                  ),
                  //custom icon without header
                  Container(
                    margin: EdgeInsets.only(
                      top: 30.0,
                      bottom: 16.0,
                      left: 16.0,
                      right: 16.0,
                    ),
                    child: new Row(
                      children: <Widget>[
                        Expanded(
                            child: Text(
                          _currentMonth,
                          style: TextStyle(
                            fontWeight: FontWeight.bold,
                            fontSize: 24.0,
                          ),
                        )),
                        FlatButton(
                          child: Text('PREV'),
                          onPressed: () {
                            setState(() {
                              _targetDateTime = DateTime(_targetDateTime.year,
                                  _targetDateTime.month - 1);
                              _currentMonth =
                                  DateFormat.yMMM().format(_targetDateTime);
                            });
                          },
                        ),
                        FlatButton(
                          child: Text('NEXT'),
                          onPressed: () {
                            setState(() {
                              _targetDateTime = DateTime(_targetDateTime.year,
                                  _targetDateTime.month + 1);
                              _currentMonth =
                                  DateFormat.yMMM().format(_targetDateTime);
                            });
                          },
                        )
                      ],
                    ),
                  ),
                  Container(
                    margin: EdgeInsets.symmetric(horizontal: 16.0),
                    // set calendar widget size percentage
                    child: _calendarCarouselNoHeader(parentHeight * 0.8, parentWidth),
                  ), //
                ],
              ),
            );
          },
        ),
      ),
    );
  }
}

更新:您也可以使用 MediaQuery来实现类似的功能。

@override
Widget build(BuildContext context) {
  var screenSize = MediaQuery.of(context).size ;
  if (screenSize.width > layoutSize){
    return Widget(); 
  } else {
    return Widget(); /// Widget if doesn't match the size
  }
}