flutter 單例

flutter中的單例

class DataSave{
  factory DataSave() => shared();
  static  DataSave _instance;
  DataSave._() {

  }
  static DataSave shared(){
    if(_instance == null){
      _instance = DataSave._();
    }
    return _instance;
  }
  //添加一個屬性 通過單例來緩存屬性值
  var a = 0;
}

使用

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    //賦值並存儲在單利中
    DataSave.shared().a = 200;
    return MaterialApp(
      title: '單例測試',
      home: Scaffold(
        appBar: AppBar(title: Text('data'),),
        body: TestPage(),
      ),
    );
  }
}

class TestPage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    //讀取單例的值
   int a =  DataSave.shared().a;
    return Scaffold(
      body: Center(
        child: Text('$a'),
      ),
    );
  }
}