vol.1 Flutter Coding Dojo

Flutter 开发者的道场，练习基本招式。精选 Stack Overflow 网站 flutter、dart 标签下的常见问题，总结为实用、简短的招式。Flutter 发布以来，受到越来越多的开发者和组织关注和使用。快速上手开发，需要了解 Dart 语言特性、Flutter 框架 SDK 及 API、惯用法、异常处理、辅助开发的工具使用等…。隐藏调试模式横幅。 return MaterialApp( title: ‘Flutter Demo’, debugShowCheckedModeBanner: false, theme: ThemeData( primarySwatch: Colors.blue, ), home: MyHomePage(title: ‘Flutter Demo Home Page’), );打印日志调试应用。import ‘package:flutter/foundation.dart’;print(’logs’);debugPrint(’logs’);当日志输出过多时，Android 系统可能会丢弃一些日志行，为了避免这种情况使用 Flutter foundation 库提供的 debugPrint() 方法。指定 App 用户界面可以显示的方向集[…]。SystemChrome.setPreferredOrientations([DeviceOrientation.portraitUp]);获取手机屏幕宽高。double width = MediaQuery.of(context).size.width;double height = MediaQuery.of(context).size.height;获取 App 可以显示的矩形边界，排除被系统 UI（状态栏）或硬件凹槽遮挡部分。EdgeInsets devicePadding = MediaQuery.of(context).padding;添加、显示图片资源。Image.asset(‘images/cat.png’)确保在 pubspec.yaml 文件中显式标识资源路径，否则将会抛出异常。flutter: assets: - images/cat.pngflutter: ══╡ EXCEPTION CAUGHT BY IMAGE RESOURCE SERVICE ╞══flutter: The following assertion was thrown resolving an image codec:flutter: Unable to load asset: assets/heart_icon.png注意：在 .yaml 类型的文件中，正确的空格缩进至关重要。导航到新页面（Route）然后返回。Navigator.push(context, MaterialPageRoute(builder: (BuildContext context) => MyPage());Navigator.pop(context);使用自定义 Widget 替换红屏 ErrorWidget。ErrorWidget.builder = (FlutterErrorDetails details) { return Container();}确保 setState() 方法不会在 dispose() 方法之后调用。if (this.mounted){ setState((){ //Your state change code goes here });}setState() 方法可能会抛出异常：throw FlutterError( ‘setState() called after dispose(): $this\n’ ‘This error happens if you call setState() on a State object for a widget that ’ ’no longer appears in the widget tree (e.g., whose parent widget no longer ’ ‘includes the widget in its build). This error can occur when code calls ’ ‘setState() from a timer or an animation callback. The preferred solution is ’ ’to cancel the timer or stop listening to the animation in the dispose() ’ ‘callback. Another solution is to check the “mounted” property of this ’ ‘object before calling setState() to ensure the object is still in the ’ ’tree.\n’ ‘This error might indicate a memory leak if setState() is being called ’ ‘because another object is retaining a reference to this State object ’ ‘after it has been removed from the tree. To avoid memory leaks, ’ ‘consider breaking the reference to this object during dispose().’ );Dart 单例设计模式，使用工厂构造函数。class Singleton { static final Singleton _singleton = Singleton._internal(); factory Singleton() { return _singleton; } Singleton._internal();}