为什么我的值没有在GetX Flutter中更新

Question

我在GetX中制作了两个非常简单的页面来学习它。我为它创建了三个变量，一个是计数器，另一个是目的地和出发地城市。计数器变量正在完美更新，而其他变量没有更改其值。它们只有在我热重新加载时才会改变。

如果你认为我遗漏了什么，或者这种怀疑很常见，并且你看到了像我这样非常相似的例子，请分享它的链接，或者如果可以的话更正代码。

这是我的课：

import 'package:get/get.dart';
class Controller extends GetxController {
var count = 0.obs;
var des = "Delhi".obs;
var dep = "Agra".obs;
void increment() {
count.value++;
update();
}
void updateDes(String input) {
des = input.obs;
}
void updateDep(String input) {
dep = input.obs;
}
}

这是第一页(您可以查看第14、30-52行(-

import 'package:flutter/material.dart';
import 'package:flutter_application_firebase_noti_basics/my_controller.dart';
import 'package:flutter_application_firebase_noti_basics/new_home.dart';
import 'package:get/get.dart';
class Sample extends StatefulWidget {
const Sample({Key? key}) : super(key: key);
@override
_SampleState createState() => _SampleState();
}
class _SampleState extends State<Sample> {
final my_controller = Get.put(Controller());
@override
Widget build(BuildContext context) {
return Scaffold(
body: Padding(
padding: EdgeInsets.all(20.0),
child: Center(
child: Container(
width: 300,
height: 300,
color: Colors.grey[400],
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
crossAxisAlignment: CrossAxisAlignment.center,
children: [
Obx(
() => InkWell(
child: Text("${my_controller.des}"),
onTap: () {
Get.to(NewHome(
num: 1,
));
},
),
),
const SizedBox(
height: 20,
),
Obx(
() => InkWell(
child: Text('${my_controller.dep}'),
onTap: () {
Get.to(NewHome(
num: 2,
));
},
),
),
],
),
),
),
),
);
}
}

这是城市选择页面(您可能想查看线路：32，93-103，121-125(-

import 'package:flutter/material.dart';
import 'package:get/get.dart';
import 'my_controller.dart';
class NewHome extends StatefulWidget {
int? num = 0;
NewHome({
Key? key,
this.num,
}) : super(key: key);
@override
_NewHomeState createState() => _NewHomeState();
}
class _NewHomeState extends State<NewHome> {
final List<Map<String, dynamic>> _allCities = [
{"id": 1, "city": "Delhi", "state": ""},
{"id": 2, "city": "Agra", "state": "UP"},
{"id": 3, "city": "Mumbai", "state": "Maharashtra"},
{"id": 4, "city": "Jaipur", "state": "Rajasthan"},
{"id": 5, "city": "Jodhpur", "state": "Rajasthan"},
{"id": 6, "city": "Ranchi", "state": "Jharkhand"},
{"id": 7, "city": "Dhanbad", "state": "Jharkhand"},
{"id": 8, "city": "Kanpur", "state": "UP"},
{"id": 9, "city": "Chandigarh", "state": "Punjab"},
{"id": 10, "city": "Meerut", "state": "UP"},
];
final controller = Get.put(Controller());
@override
Widget build(BuildContext context) {
return SafeArea(
child: Scaffold(
backgroundColor: const Color(0xffEEEDEF),
body: Column(
children: [
Padding(
padding: const EdgeInsets.symmetric(vertical: 10.0),
child: Row(
children: [
IconButton(
icon: const Icon(Icons.arrow_back),
color: Colors.orange,
onPressed: () {
Navigator.pop(context);
},
),
Container(
width: MediaQuery.of(context).size.width * 0.85,
height: 50.0,
decoration: BoxDecoration(
color: Colors.white,
borderRadius:
const BorderRadius.all(Radius.circular(5.0)),
border: Border.all(color: Colors.blueAccent)),
child: TextField(
decoration: InputDecoration(
hintText: "Enter Origin",
border: InputBorder.none,
contentPadding: const EdgeInsets.only(left: 10.0),
hintStyle: TextStyle(
fontSize: 15.0,
color: Colors.grey[500],
),
),
),
),
],
),
),
Align(
alignment: Alignment.centerLeft,
child: Padding(
padding: EdgeInsets.only(
left: MediaQuery.of(context).size.width * 0.04, top: 3.0),
child: Text(
'Popular Searches:',
style: TextStyle(
color: Colors.grey[500],
fontSize: MediaQuery.of(context).size.width * 0.035),
),
),
),
Expanded(
child: ListView.builder(
itemCount: _allCities.length,
itemBuilder: (context, index) {
return InkWell(
onTap: () {
controller.increment();
if (widget.num == 1) {
controller.updateDes(_allCities[index]['city']);
Get.back();
} else if (widget.num == 2) {
controller.updateDep(_allCities[index]['city']);
Get.back();
} else {
Get.back();
}
},
child: Padding(
padding: const EdgeInsets.only(
left: 18.0, top: 10.0, bottom: 15.0),
child: Text(
_allCities[index]['city'],
style: const TextStyle(
color: Colors.black,
fontSize: 15.0,
fontWeight: FontWeight.normal,
),
),
),
);
},
),
),
Obx(
() => Text("${controller.count} cities are selected",
style: const TextStyle(fontSize: 20.0)),
)
],
),
),
);
}
}

Answer 1

这是因为您没有正确更新值。当使用反应(obs(变量时，需要更新变量的value属性。

此外，您不应该将update与obs变量一起使用，因为它们将自动更新。所以你的控制器将是：

class Controller extends GetxController {
var count = 0.obs;
var des = "Delhi".obs;
var dep = "Agra".obs;
void increment() {
count.value++;
// removed update()
}
void updateDes(String input) {
// changing from des = input.obs
des.value = input;
}
void updateDep(String input) {
// changing from dep = input.obs
dep.value = input;
}
}

Answer 2

您需要从代码中删除update，并从字符串值中删除.obs，如下所示：

import 'package:get/get.dart';
class Controller extends GetxController {
var count = 0.obs;
var des = "Delhi".obs;
var dep = "Agra".obs;
void increment() {
count.value++;
// remove this --->   update();
}
void updateDes(String input) {
des=input
// remove this--->  des = input.obs;
}
void updateDep(String input) {
// remove this--->    dep = input.obs;
dep=input
}
}

Answer 3

import 'package:get/get.dart';
class Controller extends GetxController {
var count = 0.obs;
var des = "Delhi".obs;
var dep = "Agra".obs;
void increment() {
count.value++;

}
void updateDes(String input) {
des = input.obs;
}
void updateDep(String input) {
dep = input.obs;
}
}

在你的第一页代码中，你需要删除updated((函数，因为如果你使用obs，那么就不需要使用update((。

import 'package:flutter/material.dart';
import 'package:get/get.dart';

import 'my_controller.dart';

class NewHome extends StatefulWidget {
int? num = 0;

NewHome({
Key? key,
this.num,
}) : super(key: key);

@override
_NewHomeState createState() => _NewHomeState();
}

class _NewHomeState extends State<NewHome> {
final List<Map<String, dynamic>> _allCities = [
{"id": 1, "city": "Delhi", "state": ""},
{"id": 2, "city": "Agra", "state": "UP"},
{"id": 3, "city": "Mumbai", "state": "Maharashtra"},
{"id": 4, "city": "Jaipur", "state": "Rajasthan"},
{"id": 5, "city": "Jodhpur", "state": "Rajasthan"},
{"id": 6, "city": "Ranchi", "state": "Jharkhand"},
{"id": 7, "city": "Dhanbad", "state": "Jharkhand"},
{"id": 8, "city": "Kanpur", "state": "UP"},
{"id": 9, "city": "Chandigarh", "state": "Punjab"},
{"id": 10, "city": "Meerut", "state": "UP"},
];



@override
Widget build(BuildContext context) {
Get.lazyPut(() => Controller());// this line you need to add in your second file
return SafeArea(
child: Scaffold(
backgroundColor: const Color(0xffEEEDEF),
body: Column(
children: [
Padding(
padding: const EdgeInsets.symmetric(vertical: 10.0),
child: Row(
children: [
IconButton(
icon: const Icon(Icons.arrow_back),
color: Colors.orange,
onPressed: () {
Navigator.pop(context);
},
),
Container(
width: MediaQuery.of(context).size.width * 0.85,
height: 50.0,
decoration: BoxDecoration(
color: Colors.white,
borderRadius:
const BorderRadius.all(Radius.circular(5.0)),
border: Border.all(color: Colors.blueAccent)),
child: TextField(
decoration: InputDecoration(
hintText: "Enter Origin",
border: InputBorder.none,
contentPadding: const EdgeInsets.only(left: 10.0),
hintStyle: TextStyle(
fontSize: 15.0,
color: Colors.grey[500],
),
),
),
),
],
),
),
Align(
alignment: Alignment.centerLeft,
child: Padding(
padding: EdgeInsets.only(
left: MediaQuery.of(context).size.width * 0.04, top: 3.0),
child: Text(
'Popular Searches:',
style: TextStyle(
color: Colors.grey[500],
fontSize: MediaQuery.of(context).size.width * 0.035),
),
),
),
Expanded(
child: ListView.builder(
itemCount: _allCities.length,
itemBuilder: (context, index) {
return InkWell(
onTap: () {
controller.increment();
if (widget.num == 1) {
controller.updateDes(_allCities[index]['city']);
Get.back();
} else if (widget.num == 2) {
controller.updateDep(_allCities[index]['city']);
Get.back();
} else {
Get.back();
}
},
child: Padding(
padding: const EdgeInsets.only(
left: 18.0, top: 10.0, bottom: 15.0),
child: Text(
_allCities[index]['city'],
style: const TextStyle(
color: Colors.black,
fontSize: 15.0,
fontWeight: FontWeight.normal,
),
),
),
);
},
),
),
Obx(
() => Text("${controller.count.value} cities are selected",
style: const TextStyle(fontSize: 20.0)),
)
],
),
),
);
}
}

请检查这个第二页的代码，我现在做了一些更正，也许它会很好。

现在在第三页可以根据第二页进行更改。

Get-X Statemanagement的主要内容：-

1. 如果您使用obx，则无需使用update((函数
2. 当您要访问任何成员变量的值时，您需要使用.value。类似controller.count.value一样
3. 您需要在任何要使用GetX控制器类的屏幕中添加此行：-Get.lazyPut(((=>Controller(((；这一行将添加到Scaffold返回语句之前
4. 仅使用Obx((包裹要在其中添加观察的小部件