* dart 控制语句(if/else, switch/case, while/do-while, for) */import'package:flutter/material.dart';import'package:flutter_demo/helper.dart';classDartStatementextendsStatelessWidget{constDartStatement({Key? key}) :super(key: key);@overrideWidget build(BuildContext context) {// if/elsesample1()...
Here theTitleWidgetdoesn’t change on every build, so its better to make it a const widget. Advantage: Faster build becauseTitleWidgetwill be skipped in the build since it wont change during the process. class MyWidget extends StatelessWidget { const MyWidget({Key? key}) : super(key: key)...
I have this stateful widget (ride) where the body is one of the child stateless widgets defined in _children. The if statement just changes between the 1st and 2nd child widgets depending on if the user has connected a BT device (that part is irrelevant). What I need to ...
onAuthStateChanged(AuthState state) { if(state == AuthState.LOGGED_IN) Navigator.of(_ctx).pushReplacementNamed("/home"); } @override Widget build(BuildContext context) { _ctx = context; ...(UI for login screen) @override void onLoginError(String errorTxt) { _showSnackBar(errorTxt); s...
if(weightInKg !=null && heightInMeter !=null){ return weightInKg / (heightInMeter * heightInMeter); } } # Bad int phone_number; const pie_value=3.14; // parametrs double calculateBMI(int weight_in_kg, int height_in_meter) { ...
通过编写组件映射表,Fair可以支持更多的Widget,既可以是Flutter框架的,也可以是三方组件。 比如我们自定义了一个CustomTag组件,需要生成绑定映射组件,同时我们还想额外为 convex_bottom_bar这个社区的package组件生成映射组件。可以这么做: 生成的代码片段如下: ...
In the if statement, wait for the future to be concluded. () async => { if(await checkLoginStatus()) { // } OR Cast toFuture<bool> () async => { if(await (checkLoginStatus() as Future)) { // } Solution 2: To proceed,awaitis necessary forcheckLoginStatus()given that it curr...
A simple answer, you need to use this line, if your main function uses async keyword because you use await statement inside it. Future<void> main()async{ WidgetsFlutterBinding.ensureInitialized(); SharedPreferences prefs =awaitSharedPreferences.getInstance();// just an example} ...
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final _formKey = GlobalKey<FormState>(); Form( key: _formKey, child: Column( children: <Widget>[ TextFormField( decoration: InputDecoration(labelText: '邮箱'), validator: (value) { if (value == null || value.isEmpty) { return '请输入邮箱'; } return null; }, ), ElevatedButton(...