Dart 如何在另一个类小部件中获取自定义有状态小部件值?
在我的应用程序的第一页中,用户将选择1到10之间的编号,选择编号后,如果用户选择5,我的第二页将显示5级屏幕小部件,如wise,我可以使用下面的代码创建小部件,但我无法获得用户从我的GradeScreen小部件中的dropdownbutton小部件中选择的值 请帮助我从这个GradeScreen小部件获取值。 我是个新手。 提前谢谢Dart 如何在另一个类小部件中获取自定义有状态小部件值?,dart,flutter,Dart,Flutter,在我的应用程序的第一页中,用户将选择1到10之间的编号,选择编号后,如果用户选择5,我的第二页将显示5级屏幕小部件,如wise,我可以使用下面的代码创建小部件,但我无法获得用户从我的GradeScreen小部件中的dropdownbutton小部件中选择的值 请帮助我从这个GradeScreen小部件获取值。 我是个新手。 提前谢谢 import 'package:flutter/material.dart'; class CalculateCGPAScreen extends Statele
import 'package:flutter/material.dart';
class CalculateCGPAScreen extends StatelessWidget {
final int noOfSubjectsCount;
CalculateCGPAScreen(this.noOfSubjectsCount);
@override
Widget build(BuildContext context) {
// TODO: implement build
return Scaffold(
appBar: AppBar(),
body: Column(
children: noOfSubjects(noOfSubjectsCount),
),
);
}
List<Widget> noOfSubjects(int subjectCount) {
List<Widget> list = [];
for (int i = 1; i <= subjectCount; i++) {
list.add(GradeScreen("Subject $i", 1));
}
list.add(RaisedButton(
onPressed: () {},
color: Colors.amber,
splashColor: Colors.amberAccent,
child: Text("Calculate CGPA"),
));
return list;
}
}
class GradeScreen extends StatefulWidget {
final String subjectName;
final int gradeSystem;
GradeScreen(this.subjectName, this.gradeSystem);
@override
State<StatefulWidget> createState() {
// TODO: implement createState
return _GradeScreenState();
}
}
class _GradeScreenState extends State<GradeScreen> {
String selectedGrade = "S";
List<int> creditList = [1, 2, 3, 4, 5, 6];
int selectedCredit = 1;
@override
Widget build(BuildContext context) {
// TODO: implement build
return Row(
mainAxisAlignment: MainAxisAlignment.spaceEvenly,
children: <Widget>[
Text(widget.subjectName),
DropdownButton(
items: getGradeList(widget.gradeSystem).map((String loopValue) {
return DropdownMenuItem(
child: Text(loopValue),
value: loopValue,
);
}).toList(),
onChanged: (String value) {
setState(() {
selectedGrade = value;
});
},
value: selectedGrade,
),
DropdownButton(
items: creditList.map((int credit) {
return DropdownMenuItem(
child: Text(credit.toString()),
value: credit,
);
}).toList(),
onChanged: (int value) {
setState(() {
selectedCredit = value;
});
},
value: selectedCredit,
)
],
);
}
List<String> getGradeList(int option) {
List<String> gradeSystem;
if (option == 1) {
gradeSystem = ['S', 'A', 'B', 'C', 'D', 'E'];
} else {
gradeSystem = ['O', 'A+', 'A', 'B+', 'B'];
}
return gradeSystem;
}
}
导入“包装:颤振/材料.省道”;
类CalculateCGPAScreen扩展了无状态小部件{
最终int NOOFSUBJECTS;
CalculateCGPAScreen(this.noOfSubjectsCount);
@凌驾
小部件构建(构建上下文){
//TODO:实现构建
返回脚手架(
appBar:appBar(),
正文:专栏(
儿童:noOfSubjects(noOfSubjectsCount),
),
);
}
列表noOfSubjects(int subjectCount){
列表=[];
对于(inti=1;iimport'package:flatter/material.dart';
类CalculateCGPAScreen扩展了无状态小部件{
最终int NOOFSUBJECTS;
CalculateCGPAScreen(this.noOfSubjectsCount);
@凌驾
小部件构建(构建上下文){
//TODO:实现构建
返回脚手架(
appBar:appBar(),
正文:专栏(
儿童:noOfSubjects(noOfSubjectsCount),
),
);
}
列表noOfSubjects(int subjectCount){
列表=[];
对于(int i=1;i_数据;
}
类_GradeScreenState扩展状态{
字符串selectedGrade=“S”;
List creditList=[1,2,3,4,5,6];
int selectedCredit=1;
@凌驾
小部件构建(构建上下文){
//TODO:实现构建
返回行(
mainAxisAlignment:mainAxisAlignment.space,
儿童:[
文本(widget.subjectName),
下拉按钮(
项目:getGradeList(widget.gradeSystem).map((字符串值){
返回下拉菜单项(
子项:文本(循环值),
value:loopValue,
);
}).toList(),
onChanged:(字符串值){
设置状态(){
selectedGrade=值;
});
},
值:selectedGrade,
),
下拉按钮(
项目:creditList.map((内部信用){
返回下拉菜单项(
子项:文本(credit.toString()),
价值:信用,
);
}).toList(),
onChanged:(int值){
设置状态(){
selectedCredit=值;
widget.data=selectedCredit;
});
},
值:selectedCredit,
)
],
);
}
列表getGradeList(int选项){
列表评分系统;
如果(选项==1){
成绩系统=['S','A','B','C','D','E'];
}否则{
成绩系统=['O'、'A+'、'A'、'B+'、'B'];
}
返回分级系统;
}
}
导入“包装:颤振/材料.飞镖”;
类CalculateCGPAScreen扩展了无状态小部件{
最终int NOOFSUBJECTS;
CalculateCGPAScreen(this.noOfSubjectsCount);
@凌驾
小部件构建(构建上下文){
//TODO:实现构建
返回脚手架(
appBar:appBar(),
正文:专栏(
儿童:noOfSubjects(noOfSubjectsCount),
),
);
}
列表noOfSubjects(int subjectCount){
列表=[];
对于(int i=1;i_学分;
设置坡度(字符串值){
_等级=价值;
}
获取等级=>\u等级;
}
类_GradeScreenState扩展状态{
字符串selectedGrade=“S”;
List creditList=[1,2,3,4,5,6];
int selectedCredit=1;
@凌驾
小部件构建(构建上下文){
//TODO:实现构建
返回行(
mainAxisAlignment:mainAxisAlignment.space,
儿童:[
文本(widget.subjectName),
下拉按钮(
项目:getGradeList(widget.gradeSystem).map((字符串值){
返回下拉菜单项(
子项:文本(循环值),
value:loopValue,
);
}).toList(),
onChanged:(字符串值){
设置状态(){
selectedGrade=值;
widget.grade=值;
});
},
值:selectedGrade,
),
下拉按钮(
项目:creditList.map((内部信用){
返回下拉菜单项(
子项:文本(credit.toString()),
价值:信用,
);
}).toList(),
onChanged:(int值){
设置状态(){
selectedCredit=值;
widget.credit=价值;
});
},
值:selectedCredit,
)
],
);
}
列表getGradeList(int选项){
列表评分系统;
如果(选项==1){
成绩系统=['S','A','B','C','D','E'];
}否则{
成绩系统=['O'、'A+'、'A'、'B+'、'B'];
}
返回分级系统;
}
}
更改下拉列表值,并将结果输入调试控制台。这对我很有效,兄弟。非常感谢。我现在真的很高兴。
import 'package:flutter/material.dart';
class CalculateCGPAScreen extends StatelessWidget {
final int noOfSubjectsCount;
CalculateCGPAScreen(this.noOfSubjectsCount);
@override
Widget build(BuildContext context) {
// TODO: implement build
return Scaffold(
appBar: AppBar(),
body: Column(
children: noOfSubjects(noOfSubjectsCount),
),
);
}
List<Widget> noOfSubjects(int subjectCount) {
List<Widget> list = [];
for (int i = 1; i <= subjectCount; i++) {
list.add(GradeScreen("Subject $i", 1));
}
list.add(RaisedButton(
onPressed: () {},
color: Colors.amber,
splashColor: Colors.amberAccent,
child: Text("Calculate CGPA"),
));
return list;
}
}
class GradeScreen extends StatefulWidget {
final String subjectName;
final int gradeSystem;
int _data;
GradeScreen(this.subjectName, this.gradeSystem);
@override
State<StatefulWidget> createState() {
// TODO: implement createState
return _GradeScreenState();
}
set data(int value) {
_data = value;
}
get data => _data;
}
class _GradeScreenState extends State<GradeScreen> {
String selectedGrade = "S";
List<int> creditList = [1, 2, 3, 4, 5, 6];
int selectedCredit = 1;
@override
Widget build(BuildContext context) {
// TODO: implement build
return Row(
mainAxisAlignment: MainAxisAlignment.spaceEvenly,
children: <Widget>[
Text(widget.subjectName),
DropdownButton(
items: getGradeList(widget.gradeSystem).map((String loopValue) {
return DropdownMenuItem(
child: Text(loopValue),
value: loopValue,
);
}).toList(),
onChanged: (String value) {
setState(() {
selectedGrade = value;
});
},
value: selectedGrade,
),
DropdownButton(
items: creditList.map((int credit) {
return DropdownMenuItem(
child: Text(credit.toString()),
value: credit,
);
}).toList(),
onChanged: (int value) {
setState(() {
selectedCredit = value;
widget.data = selectedCredit;
});
},
value: selectedCredit,
)
],
);
}
List<String> getGradeList(int option) {
List<String> gradeSystem;
if (option == 1) {
gradeSystem = ['S', 'A', 'B', 'C', 'D', 'E'];
} else {
gradeSystem = ['O', 'A+', 'A', 'B+', 'B'];
}
return gradeSystem;
}
}
import 'package:flutter/material.dart';
class CalculateCGPAScreen extends StatelessWidget {
final int noOfSubjectsCount;
CalculateCGPAScreen(this.noOfSubjectsCount);
@override
Widget build(BuildContext context) {
// TODO: implement build
return Scaffold(
appBar: AppBar(),
body: Column(
children: noOfSubjects(noOfSubjectsCount),
),
);
}
List<Widget> noOfSubjects(int subjectCount) {
List<Widget> list = [];
for (int i = 1; i <= subjectCount; i++) {
list.add(GradeScreen("Subject $i", 1));
}
list.add(RaisedButton(
onPressed: () {
for (var item in list) {
if (item is GradeScreen) {
GradeScreen gs = item;
print(gs.grade);
print(gs.credit);
}
}
},
color: Colors.amber,
splashColor: Colors.amberAccent,
child: Text("Calculate CGPA"),
));
return list;
}
}
class GradeScreen extends StatefulWidget {
final String subjectName;
final int gradeSystem;
int _credit;
String _grade;
GradeScreen(this.subjectName, this.gradeSystem);
@override
State<StatefulWidget> createState() {
// TODO: implement createState
return _GradeScreenState();
}
set credit(int value) {
_credit = value;
}
get credit => _credit;
set grade(String value) {
_grade = value;
}
get grade => _grade;
}
class _GradeScreenState extends State<GradeScreen> {
String selectedGrade = "S";
List<int> creditList = [1, 2, 3, 4, 5, 6];
int selectedCredit = 1;
@override
Widget build(BuildContext context) {
// TODO: implement build
return Row(
mainAxisAlignment: MainAxisAlignment.spaceEvenly,
children: <Widget>[
Text(widget.subjectName),
DropdownButton(
items: getGradeList(widget.gradeSystem).map((String loopValue) {
return DropdownMenuItem(
child: Text(loopValue),
value: loopValue,
);
}).toList(),
onChanged: (String value) {
setState(() {
selectedGrade = value;
widget.grade = value;
});
},
value: selectedGrade,
),
DropdownButton(
items: creditList.map((int credit) {
return DropdownMenuItem(
child: Text(credit.toString()),
value: credit,
);
}).toList(),
onChanged: (int value) {
setState(() {
selectedCredit = value;
widget.credit = value;
});
},
value: selectedCredit,
)
],
);
}
List<String> getGradeList(int option) {
List<String> gradeSystem;
if (option == 1) {
gradeSystem = ['S', 'A', 'B', 'C', 'D', 'E'];
} else {
gradeSystem = ['O', 'A+', 'A', 'B+', 'B'];
}
return gradeSystem;
}
}