[英]How to fix flutter lib/main.dart errors
我是 flutter 的初學者,這是我的第一個項目。 我使用命令 flutter create 創建了一個新項目,然后我遇到了多個問題,我使用flutter doctor -v
修復了這些問題,但是現在我遇到了這些錯誤,我似乎無法找到解決它們的方法,每次我運行flutter run Running Gradle task 'assembleDebug'... 需要很長時間,然后我收到以下錯誤:
Launching lib\main.dart on sdk gphone x86 in debug mode...
Running Gradle task 'assembleDebug'...
lib/main.dart:7:37: Error: Can't find '}' to match '{'.
class MyApp extends StatelessWidget {
^
lib/main.dart:33:1: Error: Classes can't be declared inside other classes.
Try moving the class to the top-level.
class MyHomePage extends StatefulWidget {
^^^^^
lib/main.dart:33:18: Error: Expected a class member, but got 'extends'.
class MyHomePage extends StatefulWidget {
^^^^^^^
lib/main.dart:33:26: Error: A method declaration needs an explicit list of parameters.
Try adding a parameter list to the method declaration.
class MyHomePage extends StatefulWidget {
^^^^^^^^^^^^^^
lib/main.dart:51:1: Error: Classes can't be declared inside other classes.
Try moving the class to the top-level.
class _MyHomePageState extends State<MyHomePage> {
^^^^^
lib/main.dart:51:24: Error: Expected a class member, but got 'extends'.
class _MyHomePageState extends State<MyHomePage> {
^^^^^^^
lib/main.dart:51:32: Error: A method declaration needs an explicit list of parameters.
Try adding a parameter list to the method declaration.
class _MyHomePageState extends State<MyHomePage> {
^^^^^
lib/main.dart:29:13: Error: The method 'MyHomePage' isn't defined for the class 'MyApp'.
- 'MyApp' is from 'package:new_app/main.dart' ('lib/main.dart').
Try correcting the name to the name of an existing method, or defining a method named 'MyHomePage'.
home: MyHomePage(title: 'Flutter Demo Home Page'),
^^^^^^^^^^
lib/main.dart:34:19: Error: Expected ',' before this.
MyHomePage({Key key, this.title}) : super(key: key);
^^^
lib/main.dart:34:35: Error: Expected ';' after this.
MyHomePage({Key key, this.title}) : super(key: key);
^
lib/main.dart:34:37: Error: Expected an identifier, but got ':'.
MyHomePage({Key key, this.title}) : super(key: key);
^
lib/main.dart:34:37: Error: Expected ';' after this.
MyHomePage({Key key, this.title}) : super(key: key);
^
lib/main.dart:34:37: Error: Unexpected token ';'.
MyHomePage({Key key, this.title}) : super(key: key);
^
lib/main.dart:34:39: Error: Can't use 'super' as an expression.
To delegate a constructor to a super constructor, put the super call as an initializer.
MyHomePage({Key key, this.title}) : super(key: key);
^
lib/main.dart:45:16: Error: The final variable 'title' must be initialized.
Try adding an initializer ('= expression') to the declaration.
final String title;
^^^^^
lib/main.dart:48:3: Error: '_MyHomePageState' isn't a type.
_MyHomePageState createState() => _MyHomePageState();
^^^^^^^^^^^^^^^^
lib/main.dart:34:3: Error: The method 'MyHomePage' isn't defined for the class 'MyApp'.
- 'MyApp' is from 'package:new_app/main.dart' ('lib/main.dart').
Try correcting the name to the name of an existing method, or defining a method named 'MyHomePage'.
MyHomePage({Key key, this.title}) : super(key: key);
^^^^^^^^^^
lib/main.dart:34:29: Error: The getter 'title' isn't defined for the class 'MyApp'.
- 'MyApp' is from 'package:new_app/main.dart' ('lib/main.dart').
Try correcting the name to the name of an existing getter, or defining a getter or field named 'title'.
MyHomePage({Key key, this.title}) : super(key: key);
^^^^^
lib/main.dart:48:37: Error: The method '_MyHomePageState' isn't defined for the class 'MyApp'.
- 'MyApp' is from 'package:new_app/main.dart' ('lib/main.dart').
Try correcting the name to the name of an existing method, or defining a method named '_MyHomePageState'.
_MyHomePageState createState() => _MyHomePageState();
^^^^^^^^^^^^^^^^
lib/main.dart:55:5: Error: The method 'setState' isn't defined for the class 'MyApp'.
- 'MyApp' is from 'package:new_app/main.dart' ('lib/main.dart').
Try correcting the name to the name of an existing method, or defining a method named 'setState'.
setState(() {
^^^^^^^^
lib/main.dart:77:21: Error: The getter 'widget' isn't defined for the class 'MyApp'.
- 'MyApp' is from 'package:new_app/main.dart' ('lib/main.dart').
Try correcting the name to the name of an existing getter, or defining a getter or field named 'widget'.
title: Text(widget.title),
^^^^^^
FAILURE: Build failed with an exception.
* Where:
Script 'I:\Programs\flutter\packages\flutter_tools\gradle\flutter.gradle' line: 904
* What went wrong:
Execution failed for task ':app:compileFlutterBuildDebug'.
> Process 'command 'I:\Programs\flutter\bin\flutter.bat'' finished with non-zero exit value 1
* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full insights.
* Get more help at https://help.gradle.org
BUILD FAILED in 13m 24s
Exception: Gradle task assembleDebug failed with exit code 1
我找到了一個解決方案,flutter 和 dart 插件已安裝在 android 工作室中,但每次我運行 Z5ACEBC4CB70DDBB074B0AC76AAB176Z 時,我都會使用以下步驟安裝它,所以它會得到一個錯誤
flutter upgrade
flutter config --android-studio-dir="C:\Program Files\Android\Android Studio"
flutter doctor -v
flutter channel beta
flutter upgrade
然后我創建了一個新項目並啟動它並且它工作
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