共计 2288 个字符，预计需要花费 6 分钟才能阅读完成。
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.png
flutter: ══╡ 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();
}
