flutter - 在多次调用的选项卡 initstate() 之间切换

Question

在多次调用的选项卡 initstate() 之间切换。

我的标签栏 A、B、C 和 D 中有 4 个标签。

情况 (1) 如果我像从选项卡 A 切换到选项卡 B 那样切换选项卡，则它工作正常。

情况 (2) 但如果我转到选项卡 A 到 C，则选项卡“B”的 initstate() 调用两次

案例结果 (1)

flutter :A

flutter :B

案例(2)的结果

flutter :A

flutter :B

flutter :C

flutter :B

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',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

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

class _MyHomePageState extends State<MyHomePage> with SingleTickerProviderStateMixin{

  TabController _controller;

  void initState() {
    super.initState();
    _controller = TabController(length: 4, vsync: this);
    _controller.addListener(_handleSelected);
  }

  bool alarm = false;

// Function for handle tap event of tab
  void _handleSelected() async {
  }


  Widget build(BuildContext context) {
    return DefaultTabController(
      length: 4,
      child: Scaffold(
        appBar: AppBar(
          bottom: TabBar(
            controller: _controller,
            tabs: [
              Tab(text: "A"),
              Tab(text: "B"),
              Tab(text: "C"),
              Tab(text: "D"),
            ],
          ),
          actions: [
            Switch(
              value: alarm,
              onChanged: (value) {
              },
              activeTrackColor: Color(0xffff6b6b),
              activeColor: Color(0xffff0000),
            ),
          ],
        ),
        body: TabBarView(
          controller: _controller,
          children: [
            A(),
            B(),
            C(),
            D(),
          ],
        ),
      ),
    );
  }
}

Answer 1

您可以使用 IndexedStack小部件来解决此类问题。

在 _MyHomePageState使用一个变量来管理所选页面的索引；

class _MyHomePageState extends State<MyHomePage> with SingleTickerProviderStateMixin{

int _selectedPage;

/////
Your code 
/////

}

在您的脚手架工具的主体中 IndexedStack

body: IndexedStack(
          index:_selectedPage,
          children: [
            A(),
            B(),
            C(),
            D(),
          ],
        ),

现在在 _handleSelected ()方法句柄从 Controller 获取最新的页面索引并使用 setState 更新标签栏

void _handleSelected () async {
 int index = _controller.page ;// get index from controller (I am not sure about exact parameter name for selected index) ;
setState((){
_selectedPage = index;
});
}