Android studio 颤振：NoSuchMethodError是什么；吸气剂'；月份'；被调用时为null“；什么意思？（日期时间套餐）
几天前我开始使用flifter，我在这里遇到了一些关于Android studio 颤振：NoSuchMethodError是什么；吸气剂'；月份'；被调用时为null“；什么意思？（日期时间套餐）,android-studio,datetime,flutter,dart,Android Studio,Datetime,Flutter,Dart,几天前我开始使用flifter，我在这里遇到了一些关于DateTime包的问题。我正在尝试实现一种方法，该方法必须检查实际日期是星期一还是星期四等，然后返回一个值，该值将被添加到\u actualdatetime unformatted.add函数中。DateTime的add函数可能有问题，因此它无法接收方法返回值作为days 这是完整的代码。问题出在静态变量中_weekEndDatetimeUnformatted=_actualDatetimeUnformatted.add（新的持续时间（天：
DateTime\u actualdatetime unformatted.addadddays静态变量中_weekEndDatetimeUnformatted=_actualDatetimeUnformatted.add（新的持续时间（天：getWeekday（_actualDatetimeUnformatted））变量。当我将值改为50时，它会起作用
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:intl/intl.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
SystemChrome.setPreferredOrientations([
DeviceOrientation.portraitUp,
DeviceOrientation.portraitDown,
]);
return MaterialApp(
debugShowCheckedModeBanner: false,
theme: new ThemeData(
brightness: Brightness.dark,
primaryColorBrightness: Brightness.dark,
),
home: MyHomePage(),
);
}
}
class MyHomePage extends StatefulWidget {
@override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
// GETTING ACTUAL DATE
static var _actualDatetimeUnformatted = new DateTime.now();
// DATETIME OBJECT TOO, LIKE _actualDatetimeUnformatted BUT WITH A FEW DAYS ADDED TO IT (TO GET THE END OF THE WEEK!)
static var _weekEndDatetimeUnformatted = _actualDatetimeUnformatted.add(
new Duration(days: getWeekday(_actualDatetimeUnformatted))); // RED SCREEN MISTAKE SOMEWHERE HERE IN "getWeekday" method!
// GET MONTH, DAY, YEAR (AS END OF WEEK)
static getWeekday(_actualDatetimeUnformatted) {
if (_actualDatetimeUnformatted.weekday == DateTime.monday) {
return 6;
} else if (_actualDatetimeUnformatted.weekday == DateTime.tuesday) {
return 5;
} else if (_actualDatetimeUnformatted.weekday == DateTime.wednesday) {
return 4;
} else if (_actualDatetimeUnformatted.weekday == DateTime.thursday) {
return 3;
} else if (_actualDatetimeUnformatted.weekday == DateTime.friday) {
return 2;
} else if (_actualDatetimeUnformatted.weekday == DateTime.saturday) {
return 1;
} else if (_actualDatetimeUnformatted.weekday == DateTime.sunday) {
return 0;
}
}
// GET MONTH, DAY (AS START OF WEEK)
static var formatterWeekdayAll = new DateFormat("MMM d");
// GET WEEKDAY
static var formatterDay = new DateFormat("EEEE");
// GETTING WEEKDAY FOR SELECTED DAY (above the weekdays)
String _selectedDay = formatterDay.format(_actualDatetimeUnformatted);
// RETURNING WEEKDAY FOR APP TEXT AS WELL AS END OF WEEK CALCULATED FROM THE DAY OF _WEEKDAY (above the current day (_selectedDay))
String _Weekday = formatterWeekdayAll.format(_actualDatetimeUnformatted); //WORKS
String _WeekdayEnd = formatterWeekdayAll.format(_weekEndDatetimeUnformatted);
String text = "Some Note...";
@override
Widget build(BuildContext context) {
return Scaffold(
backgroundColor: Colors.black,
body: ListView(
children: <Widget>[
Stack(
children: <Widget>[
Container(
height: 380.0,
),
ShaderMask(
shaderCallback: (rect) {
return LinearGradient(
begin: Alignment.topCenter,
end: Alignment.bottomCenter,
colors: [Colors.black, Colors.transparent])
.createShader(
Rect.fromLTRB(0, 0, rect.width, rect.height));
},
blendMode: BlendMode.dstIn,
child: Image.asset('assets/milchstraße.jpg',
height: 300.0, fit: BoxFit.cover)),
RotatedBox(
quarterTurns: 0,
child: Text('Weekly Planner',
style: TextStyle(
fontSize: 55,
fontWeight: FontWeight.bold,
color: Colors.white.withOpacity(0.35),
letterSpacing: 10.0)),
),
Positioned(
top: 4.0,
right: 4.0,
child: Container(
height: 40.0,
width: 40.0,
decoration: BoxDecoration(
borderRadius: BorderRadius.circular(20.0),
color: Colors.white),
child: Center(
child: Icon(Icons.menu),
),
),
),
Positioned(
top: 2.0,
right: 5.0,
child: Container(
height: 12.0,
width: 12.0,
decoration: BoxDecoration(
borderRadius: BorderRadius.circular(6.0),
color: Color(0xFFFD3664)),
),
),
Positioned(
top: 170.0,
left: 10.0,
child: Column(
children: <Widget>[
Text("It's week:",
style: TextStyle(
fontFamily: 'Oswald-Light',
fontSize: 25.0,
fontWeight: FontWeight.w500,
color: Colors.white))
],
)),
Positioned(
top: 280.0,
left: 120.0,
child: Column(
children: <Widget>[
Text("$_selectedDay",
style: TextStyle(
fontFamily: 'Oswald-Light',
fontSize: 40.0,
fontWeight: FontWeight.w500,
color: Colors.white))
],
)),
Positioned(
top: 210.0,
left: 10.0,
child: Column(
children: <Widget>[
Row(
children: <Widget>[
Text('From $_Weekday. to $_WeekdayEnd.',
style: TextStyle(
fontFamily: 'Oswald-Light',
fontSize: 35.0,
fontWeight: FontWeight.bold,
color: Color(0xFFFD3664))),
],
)
],
)),
],
),
Row(mainAxisAlignment: MainAxisAlignment.spaceEvenly, children: [
_buildWeekDays('Monday', Icons.calendar_today, text),
_buildWeekDays('Tuesday', Icons.calendar_today, text),
_buildWeekDays('Wednesday', Icons.calendar_today, text),
_buildWeekDays('Thursday', Icons.calendar_today, text),
]),
Row(mainAxisAlignment: MainAxisAlignment.spaceEvenly, children: [
_buildWeekDays('Friday', Icons.calendar_today, text),
_buildWeekDays('Saturday', Icons.calendar_today, text),
_buildWeekDays('Sunday', Icons.calendar_today, text),
]),
]));
}
Widget _buildWeekDays(String day, iconData, text) {
return InkWell(
splashColor: Colors.transparent,
onTap: () {
_WeekPlanRoute(day, text); // MISTAKE SOMEWHERE IN THIS METHOD!!!
},
child: AnimatedContainer(
curve: Curves.easeIn,
duration: Duration(microseconds: 300),
height: _selectedDay == 'day' ? 100.0 : 100.0,
width: _selectedDay == 'day' ? 100.0 : 75.0,
color: _selectedDay == 'day' ? Color(0xFFFD3566) : Colors.transparent,
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: [
Icon(
iconData,
color: _selectedDay == day ? Colors.white : Colors.grey,
size: 40.0,
),
SizedBox(height: 10.0),
Text(day,
style: TextStyle(
fontFamily: 'Oswald-Light',
color: _selectedDay == day ? Colors.white : Colors.grey,
fontSize: 15.0))
],
)),
);
}
void _WeekPlanRoute(day, text) {
selectMenuOption(day);
Navigator.of(context).push(
MaterialPageRoute<void>(
builder: (BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(
'$day',
textAlign: TextAlign.center,
style: TextStyle(
fontFamily: 'Oswald-Light',
color: Color(0xFFFD3566),
fontWeight: FontWeight.bold,
fontSize: 35,
),
),
),
body: new Container(
margin: const EdgeInsets.symmetric(
horizontal: 10.0, vertical: 5.0),
padding: const EdgeInsets.symmetric(
horizontal: 15.0, vertical: 10.0),
decoration: new BoxDecoration(
color: Colors.green.shade200.withOpacity(0.3),
borderRadius: new BorderRadius.circular(5.0),
),
child: new IntrinsicHeight(
child: new Row(
crossAxisAlignment: CrossAxisAlignment.stretch,
children: <Widget>[
new Container(
margin: const EdgeInsets.only(
top: 4.0, bottom: 4.0, right: 10.0),
child: Text(
text, // DYNAMICALLY FOR USERS!
textAlign: TextAlign.justify,
overflow: TextOverflow.ellipsis,
maxLines: 3,
style: TextStyle(
fontFamily: 'Oswald-Light',
fontSize: 20,
fontWeight: FontWeight.w200,
color: Colors.white,
),
),
),
new Container(
margin: EdgeInsets.symmetric(horizontal: 5.0),
child: InkWell(
child: Icon(
Icons.star_border,
size: 40,
),
onTap: () {
setToFav(text);
},
onDoubleTap: () {
// DELETE COLOR FROM THE STAR
// DELETE IT FROM ARRAY OF IMPORTANT NOTES!
},
),
),
],
),
),
),
);
}
),
);
}
selectMenuOption(String day) {
setState(() {
_selectedDay = day;
});
}
setToFav(String text) {
setState(() {
//final bool favourized = _saved.contains(pair)
});
}
}
导入“包装：颤振/材料.省道”；
导入“包：flifter/services.dart”；
导入“包：intl/intl.dart”；
void main（）=>runApp（MyApp（））；
类MyApp扩展了无状态小部件{
@凌驾
小部件构建（构建上下文）{
SystemChrome.setPreferredOrientations([
DeviceOrientation.Up，
DeviceOrientation.down，
]);
返回材料PP(
debugShowCheckedModeBanner:false，
主题：新主题数据(
亮度：亮度。暗，
PrimaryColor亮度：亮度。暗，
),
主页：MyHomePage（），
);
}
}
类MyHomePage扩展StatefulWidget{
@凌驾
_MyHomePageState createState（）=>\u MyHomePageState（）；
}
类_MyHomePageState扩展状态{
//获取实际日期
静态变量_actualDatetimeUnformatted=new DateTime.now（）；
//DATETIME对象，如_ActualDateTime未格式化，但添加了几天（以获得周末！）
静态变量_weekEndDatetimeUnformatted=_actualDatetimeUnformatted.add(
新的持续时间（天：getWeekday（_actualDatetimeUnformatted））；//在“getWeekday”方法中的某个地方出现了红屏错误！
//获取月、日、年（作为周末）
静态getWeekday（_actualDatetimeUnformatted）{
如果（_actualDatetimeUnformatted.weekday==DateTime.monday）{
返回6；
}else if（_actualDatetimeUnformatted.weekday==DateTime.周二）{
返回5；
}else if（_actualDatetimeUnformatted.weekday==DateTime.周三）{
返回4；
}else if（_actualDatetimeUnformatted.weekday==DateTime.周四）{
返回3；
}如果（_actualDatetimeUnformatted.weekday==DateTime.friday）{
返回2；
}else if（_actualDatetimeUnformatted.weekday==DateTime.saturday）{
返回1；
}else if（_actualDatetimeUnformatted.weekday==DateTime.sunday）{
返回0；
}
}
//获取月、日（作为周的开始）
静态var formatterWeekdayAll=新日期格式（“MMM d”）；
//平日上班
静态var formatterDay=新的日期格式（“EEEE”）；
//获取所选日期的工作日（高于工作日）
字符串_selectedDay=formatterDay.format（_actualDatetimeUnformatted）；
//返回应用程序文本的工作日以及从_工作日（高于当前日期（_selectedDay））开始计算的周末
字符串_Weekday=formatterWeekdayAll.format（_actualDatetimeUnformatted）；//有效
字符串_WeekdayEnd=formatterWeekdayAll.format（_weekEndDatetimeUnformatted）；
String text=“一些注释…”；
@凌驾
小部件构建（构建上下文）{
返回脚手架(
背景颜色：Colors.black，
正文：ListView(
儿童：[
堆叠(
儿童：[
容器(
身高：380.0，
),
沙德尔马斯克(
着色器回调：（rect）{
返回线半径(
开始：Alignment.topCenter，
结束：对齐。底部中心，
颜色：[颜色。黑色，颜色。透明]）
.createShader(
矩形从LTRB（0，0，矩形宽度，矩形高度））；
},
blendMode:blendMode.dstIn，
子项：Image.asset（'assets/milchstraße.jpg'，
高度：300.0，适合度：BoxFit.盖），
旋转箱(
四分之一轮：0，
子项：文本（'Weekly Planner'，
样式：TextStyle(
尺码：55，
fontWeight:fontWeight.bold，
颜色：颜色。白色。不透明度（0.35），
字母间距：10.0），
),
定位(
排名：4.0，
右：4.0，
子：容器(
身高：40.0，
宽度：40.0，
装饰：盒子装饰(
边界半径：边界半径。圆形（20.0），
颜色：颜色。白色），
儿童：中心(
子：图标（图标.菜单），
),
),
),
定位(
排名：2.0，
右图：5.0，
子：容器(
身高：12.0，
宽度：12.0，
装饰：盒子装饰(
边界半径：边界半径。圆形（6.0），
颜色：颜色（0xFFFD3664）），
),
),
定位(
top:170.0，
左：10.0，
子：列(
儿童：[
文本（“本周：”，
样式：TextStyle(
fontFamily:“Oswald Light”，
I/flutter (28798): ══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
I/flutter (28798): The following NoSuchMethodError was thrown building Builder:
I/flutter (28798): The getter 'month' was called on null.
I/flutter (28798): Receiver: null
I/flutter (28798): Tried calling: month
I/flutter (28798): User-created ancestor of the error-causing widget was:
I/flutter (28798): MaterialApp
I/flutter (28798): file:///C:/Users/tim-a/Desktop/AndroidStudioProjects/Flutter/wochenplaner/lib/main.dart:14:12
I/flutter (28798): When the exception was thrown, this was the stack:
I/flutter (28798): #0 Object.noSuchMethod (dart:core-patch/object_patch.dart:50:5)
I/flutter (28798): #1 _DateFormatPatternField.formatMonth (package:intl/src/intl/date_format_field.dart:445:41)
I/flutter (28798): #2 _DateFormatPatternField.formatField (package:intl/src/intl/date_format_field.dart:367:16)
I/flutter (28798): #3 _DateFormatPatternField.format (package:intl/src/intl/date_format_field.dart:244:12)
I/flutter (28798): #4 DateFormat.format.<anonymous closure> (package:intl/src/intl/date_format.dart:255:57)
I/flutter (28798): #5 List.forEach (dart:core-patch/growable_array.dart:278:8)
I/flutter (28798): #6 DateFormat.format (package:intl/src/intl/date_format.dart:255:19)
I/flutter (28798): #7 new _MyHomePageState (package:wochenplaner/main.dart:69:44)
I/flutter (28798): #8 MyHomePage.createState (package:wochenplaner/main.dart:27:37)
I/flutter (28798): #9 new StatefulElement (package:flutter/src/widgets/framework.dart:4016:25)
I/flutter (28798): #10 StatefulWidget.createElement (package:flutter/src/widgets/framework.dart:802:38)
I/flutter (28798): #11 Element.inflateWidget (package:flutter/src/widgets/framework.dart:3091:40)
I/flutter (28798): #12 Element.updateChild (package:flutter/src/widgets/framework.dart:2896:12)
I/flutter (28798): #13 SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:5119:14)
I/flutter (28798): #14 Element.inflateWidget (package:flutter/src/widgets/framework.dart:3093:14)
I/flutter (28798): #15 Element.updateChild (package:flutter/src/widgets/framework.dart:2896:12)
I/flutter (28798): #16 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3953:16)
I/flutter (28798): #17 Element.rebuild (package:flutter/src/widgets/framework.dart:3730:5)
I/flutter (28798): #18 StatelessElement.update (package:flutter/src/widgets/framework.dart:4008:5)
I/flutter (28798): #19 Element.updateChild (package:flutter/src/widgets/framework.dart:2885:15)
I/flutter (28798): #20 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:5126:14)
I/flutter (28798): #21 Element.updateChild (package:flutter/src/widgets/framework.dart:2885:15)
I/flutter (28798): #22 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:5126:14)
I/flutter (28798): #23 Element.updateChild (package:flutter/src/widgets/framework.dart:2885:15)
I/flutter (28798): #24 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:5126:14)
I/flutter (28798): #25 Element.updateChild (package:flutter/src/widgets/framework.dart:2885:15)
I/flutter (28798): #26 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:5126:14)
I/flutter (28798): #27 Element.updateChild (package:flutter/src/widgets/framework.dart:2885:15)
I/flutter (28798): #28 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3953:16)
I/flutter (28798): #29 Element.rebuild (package:flutter/src/widgets/framework.dart:3730:5)
I/flutter (28798): #30 StatefulElement.update (package:flutter/src/widgets/framework.dart:4112:5)
I/flutter (28798): #31 Element.updateChild (package:flutter/src/widgets/framework.dart:2885:15)
I/flutter (28798): #32 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3953:16)
I/flutter (28798): #33 Element.rebuild (package:flutter/src/widgets/framework.dart:3730:5)
I/flutter (28798): #34 StatelessElement.update (package:flutter/src/widgets/framework.dart:4008:5)
I/flutter (28798): #35 Element.updateChild (package:flutter/src/widgets/framework.dart:2885:15)
I/flutter (28798): #36 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3953:16)
I/flutter (28798): #37 Element.rebuild (package:flutter/src/widgets/framework.dart:3730:5)
I/flutter (28798): #38 StatefulElement.update (package:flutter/src/widgets/framework.dart:4112:5)
I/flutter (28798): #39 Element.updateChild (package:flutter/src/widgets/framework.dart:2885:15)
I/flutter (28798): #40 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:5126:14)
I/flutter (28798): #41 Element.updateChild (package:flutter/src/widgets/framework.dart:2885:15)
I/flutter (28798): #42 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3953:16)
I/flutter (28798): #43 Element.rebuild (package:flutter/src/widgets/framework.dart:3730:5)
I/flutter (28798): #44 ProxyElement.update (package:flutter/src/widgets/framework.dart:4246:5)
I/flutter (28798): #45 _InheritedNotifierElement.update (package:flutter/src/widgets/inherited_notifier.dart:94:11)
I/flutter (28798): #46 Element.updateChild (package:flutter/src/widgets/framework.dart:2885:15)
I/flutter (28798): #47 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:5126:14)
I/flutter (28798): #48 Element.updateChild (package:flutter/src/widgets/framework.dart:2885:15)
I/flutter (28798): #49 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3953:16)
I/flutter (28798): #50 Element.rebuild (package:flutter/src/widgets/framework.dart:3730:5)
I/flutter (28798): #51 StatefulElement.update (package:flutter/src/widgets/framework.dart:4112:5)
I/flutter (28798): #52 Element.updateChild (package:flutter/src/widgets/framework.dart:2885:15)
I/flutter (28798): #53 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3953:16)
I/flutter (28798): #54 Element.rebuild (package:flutter/src/widgets/framework.dart:3730:5)
I/flutter (28798): #55 StatelessElement.update (package:flutter/src/widgets/framework.dart:4008:5)
I/flutter (28798): #56 Element.updateChild (package:flutter/src/widgets/framework.dart:2885:15)
I/flutter (28798): #57 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:5126:14)
I/flutter (28798): #58 Element.updateChild (package:flutter/src/widgets/framework.dart:2885:15)
I/flutter (28798): #59 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3953:16)
I/flutter (28798): #60 Element.rebuild (package:flutter/src/widgets/framework.dart:3730:5)
I/flutter (28798): #61 ProxyElement.update (package:flutter/src/widgets/framework.dart:4246:5)
I/flutter (28798): #62 Element.updateChild (package:flutter/src/widgets/framework.dart:2885:15)
I/flutter (28798): #63 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3953:16)
I/flutter (28798): #64 Element.rebuild (package:flutter/src/widgets/framework.dart:3730:5)
I/flutter (28798): #65 BuildOwner.buildScope (package:flutter/src/widgets/framework.dart:2340:33)
I/flutter (28798): #66 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding&PaintingBinding&SemanticsBinding&RendererBinding&WidgetsBinding.drawFrame (package:flutter/src/widgets/binding.dart:701:20)
I/flutter (28798): #67 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding&PaintingBinding&SemanticsBinding&RendererBinding._handlePersistentFrameCallback (package:flutter/src/rendering/binding.dart:285:5)
I/flutter (28798): #68 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:1033:15)
I/flutter (28798): #69 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:975:9)
I/flutter (28798): #70 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding.scheduleWarmUpFrame.<anonymous closure> (package:flutter/src/scheduler/binding.dart:784:7)
I/flutter (28798): #72 _Timer._runTimers (dart:isolate-patch/timer_impl.dart:382:19)
I/flutter (28798): #73 _Timer._handleMessage (dart:isolate-patch/timer_impl.dart:416:5)
I/flutter (28798): #74 _RawReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:172:12)
I/flutter (28798): (elided one frame from package dart:async-patch)
I/flutter (28798): ════════════════════════════════════════════════════════════════════════════════════════════════════
var _weekEndDatetimeUnformatted = Jiffy().endOf(Units.WEEK);
// You can also pass a DateTime object
var _weekEndDatetimeUnformatted = Jiffy(DateTime.now()).endOf(Units.WEEK);
// And in your case
var _weekEndDatetimeUnformatted = Jiffy(_actualDatetimeUnformatted).endOf(Units.WEEK);
var _selectedDay = Jiffy(_actualDatetimeUnformatted).format("EEEE");
var _Weekday = Jiffy(_actualDatetimeUnformatted).format("MMM d");
// You can also use default formats
var formatterDay = Jiffy(_actualDatetimeUnformatted).EEEE; // e.g Monday
//User the _weekEndDatetimeUnformatted Datetime Object
var _WeekdayEnd = Jiffy(_weekEndDatetimeUnformatted).format("MMM d");
// Or use method cascading which returns a Jiffy instance.
// Advantage is that Jiffy has more functionality than DateTime
var _weekEndDatetimeUnformatted = Jiffy().endOf(Units.WEEK);
var _WeekdayEnd = _weekEndDatetimeUnformatted.format("MMM d");