GetX 不知道/看不到数据库数据何时更改/更新。
您需要告诉 GetX 在适当的时候重建。
如果您将 GetX observables 与 GetX 或 Obx 小部件一起使用，那么您只需为您的 observable 字段分配一个新值。当obs 值更改时，将进行重建。
如果您将 GetX 与 GetBuilder<MyController> 一起使用，则需要在 MyController 中调用 update() 方法来重建 GetBuilder<MyController> 小部件。
以下解决方案使用 GetX 控制器（即TabX）来：
-
保持应用状态：
- 所有选项卡列表 (
tabPages)
- 哪个选项卡处于活动状态 (
selectedIndex)
-
公开更改活动/可见选项卡的方法 (onItemTapped())
OnItemTapped()
此方法在 TabX 内部，即 GetXController。
当被调用时，它将：
- 设置哪个标签可见
- 将查看的选项卡保存到数据库 (
FakeDB)
- 使用
update() 重建任何GetBuilder 小部件
void onItemTapped(int index) {
selectedIndex = index;
db.insertViewedPage(index); // simulate database update while tabs change
update(); // ← rebuilds any GetBuilder<TabX> widget
}
完整示例
将整个代码复制/粘贴到应用中的 dart 页面中，以查看有效的 BottomNavigationBar 页面。
这个选项卡式/BottomNavigationBar 示例取自
https://api.flutter.dev/flutter/material/BottomNavigationBar-class.html
但编辑为使用 GetX。
import 'package:flutter/material.dart';
import 'package:get/get.dart';
void main() {
runApp(MyApp());
}
class MyApp extends StatelessWidget {
// This widget is the root of your application.
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
debugShowCheckedModeBanner: false,
theme: ThemeData(
primarySwatch: Colors.blue,
visualDensity: VisualDensity.adaptivePlatformDensity,
),
home: MyTabHomePage(),
);
}
}
class FakeDB {
List<int> viewedPages = [0];
void insertViewedPage(int page) {
viewedPages.add(page);
}
}
/// BottomNavigationBar page converted to GetX. Original StatefulWidget version:
/// https://api.flutter.dev/flutter/material/BottomNavigationBar-class.html
class TabX extends GetxController {
TabX({this.db});
final FakeDB db;
int selectedIndex = 0;
static const TextStyle optionStyle =
TextStyle(fontSize: 30, fontWeight: FontWeight.bold);
List<Widget> tabPages;
@override
void onInit() {
super.onInit();
tabPages = <Widget>[
ListViewTab(db),
Text(
'Index 1: Business',
style: optionStyle,
),
Text(
'Index 2: School',
style: optionStyle,
),
];
}
/// INTERESTING PART HERE ↓ ************************************
void onItemTapped(int index) {
selectedIndex = index;
db.insertViewedPage(index); // simulate database update while tabs change
update(); // ← rebuilds any GetBuilder<TabX> widget
// ↑ update() is like setState() to anything inside a GetBuilder using *this*
// controller, i.e. GetBuilder<TabX>
// Other GetX controllers are not affected. e.g. GetBuilder<BlahX>, not affected
// by this update()
// Use async/await above if data writes are slow & must complete before updating widget.
// This example does not.
}
}
/// REBUILT when Tab Page changes, rebuilt by GetBuilder in MyTabHomePage
class ListViewTab extends StatelessWidget {
final FakeDB db;
ListViewTab(this.db);
@override
Widget build(BuildContext context) {
return ListView.builder(
itemCount: db.viewedPages.length,
itemBuilder: (context, index) =>
ListTile(
title: Text('Page Viewed: ${db.viewedPages[index]}'),
),
);
}
}
class MyTabHomePage extends StatelessWidget {
@override
Widget build(BuildContext context) {
Get.put(TabX(db: FakeDB()));
return Scaffold(
appBar: AppBar(
title: const Text('BottomNavigationBar Sample'),
),
body: Center(
/// ↓ Tab Page currently visible - rebuilt by GetBuilder when
/// ↓ TabX.onItemTapped() called
child: GetBuilder<TabX>(
builder: (tx) => tx.tabPages.elementAt(tx.selectedIndex)
),
),
/// ↓ BottomNavBar's highlighted/active item, rebuilt by GetBuilder when
/// ↓ TabX.onItemTapped() called
bottomNavigationBar: GetBuilder<TabX>(
builder: (tx) => BottomNavigationBar(
items: const <BottomNavigationBarItem>[
BottomNavigationBarItem(
icon: Icon(Icons.home),
label: 'Home',
),
BottomNavigationBarItem(
icon: Icon(Icons.business),
label: 'Business',
),
BottomNavigationBarItem(
icon: Icon(Icons.school),
label: 'School',
),
],
currentIndex: tx.selectedIndex,
selectedItemColor: Colors.amber[800],
onTap: tx.onItemTapped,
),
),
);
}
}