title: flutter code display error in visual studio code
body: <p>Initially this code is correct but after I reinstalled Windows and its applications, the project that was correct is now an error.</p>
  <p><a href="https://i.stack.imgur.com/lsJYc.png" rel="nofollow noreferrer">My project error</a></p>
  <p>flutter doctor -v :</p>
  <pre><code>[√] Flutter (Channel dev, 1.26.0-1.0.pre, on Microsoft Windows [Version 10.0.19042.804], locale en-US)
      • Flutter version 1.26.0-1.0.pre at F:\src\flutter
      • Framework revision 63062a6443 (9 weeks ago), 2020-12-13 23:19:13 +0800
      • Engine revision 4797b06652
      • Dart version 2.12.0 (build 2.12.0-141.0.dev)
  
  [√] Android toolchain - develop for Android devices (Android SDK version 30.0.3)
      • Android SDK at F:\src\Android\Sdk
      • Platform android-30, build-tools 30.0.3
      • Java binary at: C:\Program Files\Android\Android Studio\jre\bin\java
      • Java version OpenJDK Runtime Environment (build 1.8.0_242-release-1644-b01)
      • All Android licenses accepted.
  
  [√] Android Studio (version 4.1.0)
      • Android Studio at C:\Program Files\Android\Android Studio
      • Flutter plugin can be installed from:
         https://plugins.jetbrains.com/plugin/9212-flutter
      • Dart plugin can be installed from:
         https://plugins.jetbrains.com/plugin/6351-dart
      • Java version OpenJDK Runtime Environment (build 1.8.0_242-release-1644-b01)
  
  [√] VS Code (version 1.53.2)
      • VS Code at C:\Users\hyda\AppData\Local\Programs\Microsoft VS Code
      • Flutter extension version 3.19.0
  
  [√] Connected device (1 available)
      • sdk gphone x86 (mobile) • emulator-5554 • android-x86 • Android 11 (API 30) (emulator)
  
  • No issues found!
  </code></pre>