Flutter 通过下拉按钮将问题移动到另一页
所以基本上我试图通过点击dropdownButton来改变一个页面，由于某种原因我得到了这个错误 我曾尝试用材料/脚手架包装东西，但都不起作用。 有什么帮助吗Flutter 通过下拉按钮将问题移动到另一页,flutter,Flutter,所以基本上我试图通过点击dropdownButton来改变一个页面，由于某种原因我得到了这个错误 我曾尝试用材料/脚手架包装东西，但都不起作用。 有什么帮助吗 import 'package:flutter/material.dart'; import 'package:intergrative2020_UI_Rest/screens/signup.dart'; class AdminPermissions extends StatefulWidget { @override _Ad
import 'package:flutter/material.dart';
import 'package:intergrative2020_UI_Rest/screens/signup.dart';
class AdminPermissions extends StatefulWidget {
@override
_AdminPermissionsState createState() => _AdminPermissionsState();
}
class _AdminPermissionsState extends State<AdminPermissions> {
var _currencies = ['Create User','Delete User','Search User'];
var _currentItemSelected = '';
@override
void initState() {
super.initState();
_currentItemSelected = _currencies[0];
}
@override
Widget build(BuildContext context) {
return MaterialApp(
home:Scaffold(
body: DropdownButton<String>(
items: _currencies.map((String value) {
return DropdownMenuItem(
value: value,
child: Text(value),
);
}).toList(),
value: _currentItemSelected,
onChanged: (String newValueSelected) {
// Your code to execute, when a menu item is selected from dropdown
_onDropDownItemSelected(newValueSelected);
switch(newValueSelected){
case "Create User" :{
Navigator.pushReplacement(context, MaterialPageRoute(builder: (BuildContext context) => Signup()));
break;
}
}
}
),
),
);
}
void _onDropDownItemSelected(String newValueSelected) {
setState(() {
this._currentItemSelected = newValueSelected;
});
}
}
import 'package:flutter/material.dart';
import 'package:intergrative2020_UI_Rest/screens/signup.dart';
class AdminPermissions extends StatefulWidget {
@override
_AdminPermissionsState createState() => _AdminPermissionsState();
}
class _AdminPermissionsState extends State<AdminPermissions> {
var _currencies = ['Create User','Delete User','Search User'];
var _currentItemSelected = '';
@override
void initState() {
super.initState();
_currentItemSelected = _currencies[0];
}
@override
Widget build(BuildContext context) {
return MaterialApp(
home:Scaffold(
body: DropdownButton<String>(
items: _currencies.map((String value) {
return DropdownMenuItem(
value: value,
child: Text(value),
);
}).toList(),
value: _currentItemSelected,
onChanged: (String newValueSelected) {
// Your code to execute, when a menu item is selected from dropdown
_onDropDownItemSelected(newValueSelected);
switch(newValueSelected){
case "Create User" :{
Navigator.pushReplacement(context, MaterialPageRoute(builder: (BuildContext context) => Signup()));
break;
}
}
}
),
),
);
}
void _onDropDownItemSelected(String newValueSelected) {
setState(() {
this._currentItemSelected = newValueSelected;
});
}
}
import 'package:flutter/material.dart';
import 'package:intergrative2020_UI_Rest/screens/signup.dart';
class AdminPermissions extends StatefulWidget {
@override
_AdminPermissionsState createState() => _AdminPermissionsState();
}
class _AdminPermissionsState extends State<AdminPermissions> {
var _currencies = ['Create User','Delete User','Search User'];
var _currentItemSelected = '';
@override
void initState() {
super.initState();
_currentItemSelected = _currencies[0];
}
@override
Widget build(BuildContext context) {
return MaterialApp(
home:Scaffold(
body: DropdownButton<String>(
items: _currencies.map((String value) {
return DropdownMenuItem(
value: value,
child: Text(value),
);
}).toList(),
value: _currentItemSelected,
onChanged: (String newValueSelected) {
// Your code to execute, when a menu item is selected from dropdown
_onDropDownItemSelected(newValueSelected);
switch(newValueSelected){
case "Create User" :{
Navigator.pushReplacement(context, MaterialPageRoute(builder: (BuildContext context) => Signup()));
break;
}
}
}
),
),
);
}
void _onDropDownItemSelected(String newValueSelected) {
setState(() {
this._currentItemSelected = newValueSelected;
});
}
}
import 'package:flutter/material.dart';
import 'package:intergrative2020_UI_Rest/screens/signup.dart';
class AdminPermissions extends StatefulWidget {
@override
_AdminPermissionsState createState() => _AdminPermissionsState();
}
class _AdminPermissionsState extends State<AdminPermissions> {
var _currencies = ['Create User','Delete User','Search User'];
var _currentItemSelected = '';
@override
void initState() {
super.initState();
_currentItemSelected = _currencies[0];
}
@override
Widget build(BuildContext context) {
return MaterialApp(
home:Scaffold(
body: DropdownButton<String>(
items: _currencies.map((String value) {
return DropdownMenuItem(
value: value,
child: Text(value),
);
}).toList(),
value: _currentItemSelected,
onChanged: (String newValueSelected) {
// Your code to execute, when a menu item is selected from dropdown
_onDropDownItemSelected(newValueSelected);
switch(newValueSelected){
case "Create User" :{
Navigator.pushReplacement(context, MaterialPageRoute(builder: (BuildContext context) => Signup()));
break;
}
}
}
),
),
);
}
void _onDropDownItemSelected(String newValueSelected) {
setState(() {
this._currentItemSelected = newValueSelected;
});
}
}
导入“包装：颤振/材料.省道”；
导入“package:Integrative2020_UI_Rest/screens/signup.dart”；
类AdminPermissions扩展了StatefulWidget{
@凌驾
_AdminPermissionsState createState（）=>\u AdminPermissionsState（）；
}
类_AdminPermissionsState扩展状态{
var_currency=[“创建用户”、“删除用户”、“搜索用户”]；
var_currentItemSelected=''；
@凌驾
void initState（）{
super.initState（）；
_currentItemSelected=_货币[0]；
}
@凌驾
小部件构建（构建上下文）{
返回材料PP(
家：脚手架(
正文：下拉按钮(
项目：_currences.map（（字符串值）{
返回下拉菜单项(
价值：价值，
子项：文本（值），
);
}).toList（），
值：_currentItemSelected，
onChanged:（字符串newValueSelected）{
//从下拉列表中选择菜单项时要执行的代码
_onDropDownItemSelected（newValueSelected）；
开关（newValueSelected）{
案例“创建用户”：{
pushReplacement（context，MaterialPageRoute（builder:（BuildContext context）=>Signup（））；
打破
}
}
}
),
),
);
}
void _onDropDownItemSelected（字符串newValueSelected）{
设置状态（）{
此._currentItemSelected=newValueSelected；
});
}
}
MaterialAppScaffold下拉按钮。
因此，请尝试包装您的下拉按钮
，如下所示：
MaterialApp(
title://Title
home:Scaffold(
body:DropdownButton(
.....
.....
)
)
)
应用程序的小部件层次结构应该是MaterialApp
->Scaffold
->下拉按钮。
因此，请尝试包装您的下拉按钮
，如下所示：
MaterialApp(
title://Title
home:Scaffold(
body:DropdownButton(
.....
.....
)
)
)
尝试使用MaterialApp
。尝试使用MaterialApp
。