真机调试 Flutter 报错：Lookup failed: title in @getters in MyHomePage in package:flutter_demo02/main.dart

发生缘由

学习 Flutter 更改 lib 目录下面的 main.dart 文件之后真机调试运行 flutter run 报错：

# 小组件库异常
══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
# 构建MyHomePage的时候抛出下列_CompileTimeError
The following _CompileTimeError was thrown building MyHomePage(dirty, dependencies:
[_InheritedTheme, _LocalizationsScope-[GlobalKey#34833]], state: _MyHomePageState#2db8a):
# 查找失败：包 MyHomePage 中 @getters 中的标题：flutter_demo02/main.dart
Lookup failed: title in @getters in MyHomePage in package:flutter_demo02/main.dart

# 相关的导致错误的小部件是：MyHomePage
The relevant error-causing widget was:
  MyHomePage
  MyHomePage:file:///D:/Prog/flutter/material/flutter_proj/flutter_demo02/lib/main.dart:34:19

When the exception was thrown, this was the stack:
#0      StatefulElement.build (package:flutter/src/widgets/framework.dart:5583:27)
#1      ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:5471:15)
#2      StatefulElement.performRebuild (package:flutter/src/widgets/framework.dart:5634:11)
#3      Element.rebuild (package:flutter/src/widgets/framework.dart:5187:7)
#4      BuildOwner.buildScope (package:flutter/src/widgets/framework.dart:2895:19)
#5      WidgetsBinding.drawFrame (package:flutter/src/widgets/binding.dart:984:21)
#6      RendererBinding._handlePersistentFrameCallback (package:flutter/src/rendering/binding.dart:457:5)
#7      SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:1325:15)
#8      SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:1255:9)
#9      SchedulerBinding.scheduleWarmUpFrame.<anonymous closure> (package:flutter/src/scheduler/binding.dart:978:7)   
#13     _RawReceivePort._handleMessage (dart:isolate-patch/isolate_patch.dart:184:12)
(elided 3 frames from class _Timer and dart:async-patch)

main.dart 文件内容如下：

import 'package:flutter/material.dart';

void main() {
    // 顶层组件MaterialApp，它封装了应用程序实现 Material Design 所需要的一些 Widget。
    runApp(MaterialApp(
        // 基础布局组件Scaffold 是MaterialDesign布局结构的实现 提供了显示drawer、snackbar和底部sheet的API
        home: Scaffold(
            appBar: AppBar(title: const Text("你好Flutter")),
            // 抽离出来了一个HomeWidget的组件
            body: const HomeWidget(),
        ),
    ));
}

// 自定义组件其实就是一个类，这个类需要继承StatelessWidget或者StatefulWidget
// StatelessWidget 是无状态组件，状态不可变的widget
class HomeWidget extends StatelessWidget {
    // 构造函数调用父类的构造函数
    const HomeWidget({Key? key}) : super(key: key);

    @override
    Widget build(BuildContext context) {
        return const Center(
            child: Text(
                "我是一个文本",
                textDirection: TextDirection.ltr,
                style: TextStyle(
                    fontSize: 40.0,
                    // color: Colors.yellow,
                    color: Color.fromRGBO(244, 233, 121, 0.5),
                ),
            ),
        );
    }
}

运行环境

• 电脑系统版本：Windows 10 64bit

• VS Code：1.72.0(user setup)

• Flutter：3.16.0

# 查看Flutter版本
C:\Windows\System32>flutter --version
Flutter 3.16.0 • channel stable • https://github.com/flutter/flutter.git
Framework • revision db7ef5bf9f (4 weeks ago) • 2023-11-15 11:25:44 -0800
Engine • revision 74d16627b9
Tools • Dart 3.2.0 • DevTools 2.28.2

问题解决

问题出在 test 目录下面的 widget_test.dart 文件，正是它让项目构建失败了。因为修改完 main.dart 文件之后导致MyApp 组件，因此该测试文件就会出错。

解决原因很简单：

• 将测试文件删掉

• 亦或是将 HomeWidget 类更改为 MyApp。

最后告诫

删除掉文件亦或是修改完之后如果 r 键没有作用，那么可以 R 键。

常用快捷键	作用
r 键	点击后热加载，也就算是重新加载吧
R键	热重启项目
p 键	显示网格，这个可以很好的掌握布局情况，工作中很有用
o 键	切换android和ios的预览模式
q 键	退出调试预览模式