我正在使用Flutter开发预订应用程序。因此，想法是用户填写表格并将该信息数据传递到另一个屏幕。
下面的代码是表单屏幕。
class Other extends StatefulWidget {
final Trip trip;
Other({Key key, this.trip}) : super(key: key);
@override
_OtherState createState() => _OtherState();
}
class _OtherState extends State<Other> {
int _selectedIndex;
List<String> _options = ['Regular', 'Hard Sleeper', 'Soft Sleeper'];
DateTime _startDate = DateTime.now();
DateTime _endDate = DateTime.now().add(Duration(days: 7));
var adultNum = [1, 2, 3, 4, 5, 6, 7, 8, 9];
var adultSel = 1;
var childNum = [0, 1, 2, 3, 4, 5];
var childSel = 0;
var infantNum = [0, 1, 2];
var infantSel = 0;
var from = [
'Addis Ababa', 'Adama', 'Dire Dawa', 'Ali Sabieh', 'Djibouti'
];
var fromSel = 'Addis Ababa';
var to = [
'Addis Ababa', 'Adama', 'Dire Dawa', 'Ali Sabieh', 'Djibouti'
];
var toSel = 'Djibouti';
Future displayDateRangePicker(BuildContext context) async {
final List<DateTime> picked = await DateRagePicker.showDatePicker(
context: context,
initialFirstDate: _startDate,
initialLastDate: _endDate,
firstDate: new DateTime(DateTime
.now()
.year),
lastDate: new DateTime(DateTime
.now()
.year + 2),
);
if (picked != null && picked.length == 2) {
setState(() {
_startDate = picked[0];
_endDate = picked[1];
});
}
}
Widget _buildChips() {
List<Widget> chips = new List();
for (int i = 0; i < _options.length; i++) {
ChoiceChip choiceChip = ChoiceChip(
selected: _selectedIndex == i,
label: Text(_options[i], style: TextStyle(color: Colors.white)),
//avatar: FlutterLogo(),
elevation: 3,
pressElevation: 5,
//shadowColor: Colors.teal,
backgroundColor: Colors.grey[400],
selectedColor: Colors.lightGreen,
onSelected: (bool selected) {
setState(() {
if (selected) {
_selectedIndex = i;
}
});
},
);
chips.add(choiceChip);
}
return Row(
mainAxisAlignment: MainAxisAlignment.spaceEvenly,
children: chips,
);
}
@override
Widget build(BuildContext context) {
final Trip newTrip = new Trip('regular', DateTime.now() , 'null', 1, 0, 0, DateTime.now(), 'null');
return Container(
child: Padding(
padding: const EdgeInsets.symmetric(horizontal: 10, vertical: 10),
child: Container(
//height: 203,
child: Column(
children: [
SizedBox(height: 15,),
Container(
//decoration: BoxDecoration(border: Border.all(color: Colors.grey)),
child: Row(
mainAxisAlignment: MainAxisAlignment.spaceEvenly,
children: [
Container(
width: MediaQuery.of(context).size.width/2-19,
height: 60,
padding: EdgeInsets.symmetric(horizontal: 15),
child: Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: [
Text('From', style: TextStyle(
fontSize: 18,
color: Colors.grey
),),
SizedBox(height: 0,),
Expanded(
child: DropdownButton<String>(
underline: Container(color: Colors.transparent),
items: from.map((String value) {
return DropdownMenuItem<String>(
value: value,
child: Text(value, style: TextStyle(
fontSize: 18
),),
);
}).toList(),
isExpanded: true,
isDense: false,
elevation: 5,
hint: Text('From'),
value: fromSel,
onChanged: (String newValue){
setState(() {
this.fromSel = newValue;
});
}),
),
],
),
),
Container(height: 50, child: VerticalDivider(color: Colors.grey)),
Container(
width: MediaQuery.of(context).size.width/2-19,
height: 60,
padding: EdgeInsets.symmetric(horizontal: 15),
child: Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: [
Text('To', style: TextStyle(
fontSize: 18,
color: Colors.grey
),),
SizedBox(height: 0,),
Expanded(
child: DropdownButton<String>(
underline: Container(color: Colors.transparent),
items: to.map((String value) {
return DropdownMenuItem<String>(
value: value,
child: Text(value, style: TextStyle(
fontSize: 18
),),
);
}).toList(),
isExpanded: true,
isDense: false,
elevation: 5,
hint: Text('to'),
value: toSel,
onChanged: (String newValue){
setState(() {
this.toSel = newValue;
});
}),
),
],
),
),
],
),
),
Padding(
padding: const EdgeInsets.symmetric(horizontal: 15),
child: Divider(thickness: 1.0,),
),
Container(
height: 60,
width: MediaQuery.of(context).size.width,
//decoration: BoxDecoration(border: Border.all(color: Colors.grey)),
child: Row(
mainAxisAlignment: MainAxisAlignment.spaceEvenly,
children: [
InkWell(
child: Container(
// decoration: BoxDecoration(
// border: Border.all(color: Colors.grey)
// ),
width: MediaQuery.of(context).size.width/2-19,
height: 60,
child: Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: [
Padding(
padding: const EdgeInsets.only(top: 10, left: 10),
child: Text(
"Depart date",
style: TextStyle(
fontSize: 18, color: Colors.black54),
),
),
Padding(
padding: const EdgeInsets.only(top: 15, left: 10),
child: Text(
"${_startDate.day}/${_startDate
.month}/${_startDate.year}",
style: TextStyle(
fontSize: 15, color: Colors.black),
),
),
],
),
),
onTap: () async {
await displayDateRangePicker(context);
}
),
Container(height: 50, child: VerticalDivider(color: Colors.grey)),
InkWell(
child: Container(
// decoration: BoxDecoration(
// border: Border.all(color: Colors.grey)
// ),
width: MediaQuery.of(context).size.width/2-19,
height: 60,
child: Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: [
Padding(
padding: const EdgeInsets.only(top: 10, left: 10),
child: Text(
"Return date",
style: TextStyle(
fontSize: 18, color: Colors.black54),
),
),
Padding(
padding: const EdgeInsets.only(top: 15, left: 10),
child: Text(
"${_endDate.day}/${_endDate.month}/${_endDate
.year}",
style: TextStyle(
fontSize: 15, color: Colors.black),
),
),
],
),
),
onTap: () async {
await displayDateRangePicker(context);
},
),
],
),
),
Padding(
padding: const EdgeInsets.symmetric(horizontal: 15),
child: Divider(thickness: 1.0,),
),
Container(
height: 60,
width: MediaQuery.of(context).size.width,
child: Row(
mainAxisAlignment: MainAxisAlignment.spaceEvenly,
children: [
Icon(Elusive.person, size: 20,),
Container(
width: 65,
height: 60,
padding: EdgeInsets.symmetric(horizontal: 15),
child: Column(
children: [
Text('Adult', style: TextStyle(
fontSize: 18,
color: Colors.grey
),),
Expanded(
child: DropdownButton<int>(
underline: Container(color: Colors.transparent),
items: adultNum.map((int value) {
return DropdownMenuItem<int>(
value: value,
child: Text('$value', style: TextStyle(
fontSize: 18
),),
);
}).toList(),
isExpanded: true,
isDense: false,
elevation: 5,
value: adultSel,
onChanged: (int newValue){
setState(() {
this.adultSel = newValue;
});
}),
),
],
),
),
Container(height: 50, child: VerticalDivider(color: Colors.grey)),
Icon(Elusive.person, size: 15,),
Container(
width: 65,
height: 60,
padding: EdgeInsets.symmetric(horizontal: 15),
child: Column(
children: [
Text('Child', style: TextStyle(
fontSize: 18,
color: Colors.grey
),),
Expanded(
child: DropdownButton<int>(
underline: Container(color: Colors.transparent),
items: childNum.map((int value) {
return DropdownMenuItem<int>(
value: value,
child: Text('$value', style: TextStyle(
fontSize: 18
),),
);
}).toList(),
isExpanded: true,
isDense: false,
elevation: 5,
value: childSel,
onChanged: (int newValue){
setState(() {
this.childSel = newValue;
});
}),
),
],
),
),
Container(height: 50, child: VerticalDivider(color: Colors.grey)),
Icon(Icons.child_friendly, size: 20,),
Container(
width: 70,
height: 60,
padding: EdgeInsets.symmetric(horizontal: 15),
child: Column(
children: [
Text('Infant', style: TextStyle(
fontSize: 18,
color: Colors.grey
),),
Expanded(
child: DropdownButton<int>(
underline: Container(color: Colors.transparent),
items: infantNum.map((int value) {
return DropdownMenuItem<int>(
value: value,
child: Text('$value', style: TextStyle(
fontSize: 18
),),
);
}).toList(),
isExpanded: true,
isDense: false,
elevation: 5,
value: infantSel,
onChanged: (int newValue){
setState(() {
this.infantSel = newValue;
});
}),
),
],
),
),
],
),
),
Padding(
padding: const EdgeInsets.symmetric(horizontal: 15),
child: Divider(thickness: 1.0,),
),
Padding(
padding: const EdgeInsets.symmetric(horizontal: 10),
child: Container(
child: _buildChips(),
),
),
Padding(
padding: const EdgeInsets.symmetric(horizontal: 45),
child: Divider(thickness: 1.0,),
),
Padding(
padding: const EdgeInsets.symmetric(vertical: 20, horizontal: 10),
child: MaterialButton(
onPressed: (){
widget.trip.from = fromSel;
widget.trip.to = toSel;
widget.trip.departDate = _startDate;
widget.trip.returnDate = _endDate;
widget.trip.adult = adultSel;
widget.trip.child = childSel;
widget.trip.infant = infantSel;
widget.trip.cabinClass = _selectedIndex;
Navigator.of(context).push(MaterialPageRoute(builder: (context) => Search(trip: newTrip,)));
//Navigator.of(context).pushNamed(Other.Search, arguments: newTrip);
},
minWidth: MediaQuery
.of(context)
.size
.width - 80,
height: 45,
shape:
RoundedRectangleBorder(borderRadius: BorderRadius.circular(20)),
color: Colors.lightGreen,
splashColor: Colors.green,
child: Text(
"Search",
style: TextStyle(color: Colors.white, fontSize: 18),
),
),
)
],
),
),
),
);
}
}
，下面的代码是第二个屏幕。
class Search extends StatefulWidget {
final Trip trip;
//Search({this.trip});
Search({Key key, @required this.trip}) : super(key: key);
@override
_SearchState createState() => _SearchState();
}
class _SearchState extends State<Search> {
@override
Widget build(BuildContext context) {
return Scaffold(
body: Column(
children: [
Center(
child: Column(
children: [
Text(widget.trip.from),
Text(widget.trip.to),
Text('${widget.trip.departDate}'),
Text('${widget.trip.returnDate}'),
Text(widget.trip.cabinClass),
Text(widget.trip.adult),
Text(widget.trip.child),
Text(widget.trip.infant),
],
),
),
MaterialButton(
onPressed: (){
Navigator.push(context, MaterialPageRoute(builder: (context)=> Budget()));
}
)
],
),
);
}
}
存储数据的列表如下所示。
class Trip{
String from;
String to;
DateTime departDate;
DateTime returnDate;
var cabinClass;
var adult;
var child;
var infant;
Trip(this.cabinClass,this.departDate,this.from,this.adult,this.child,this.infant,this.returnDate,this.to);
}
所以当我运行此命令时，下面的错误会弹出
════════ Exception caught by gesture ═══════════════════════════════════════════════════════════════
The following NoSuchMethodError was thrown while handling a gesture:
The setter 'from=' was called on null.
Receiver: null
Tried calling: from="Addis Ababa"
When the exception was thrown, this was the stack:
#0 Object.noSuchMethod (dart:core-patch/object_patch.dart:51:5)
#1 _OtherState.build.<anonymous closure> (package:demo/BookingPages/other.dart:408:33)
#2 _InkResponseState._handleTap (package:flutter/src/material/ink_well.dart:993:19)
#3 _InkResponseState.build.<anonymous closure> (package:flutter/src/material/ink_well.dart:1111:38)
#4 GestureRecognizer.invokeCallback (package:flutter/src/gestures/recognizer.dart:183:24)
...
Handler: "onTap"
Recognizer: TapGestureRecognizer#fa011
debugOwner: GestureDetector
state: possible
won arena
finalPosition: Offset(167.3, 547.8)
finalLocalPosition: Offset(127.3, 34.3)
button: 1
sent tap down
那么我该如何解决。
答案 0 :(得分：0)
您尚未将trip参数传递给Other类。因此，当您尝试在from方法中设置onPressed参数时会出现错误。调用时，请尝试将非null trip参数传递给Other类。