安装Dart出错

安装 Dart 的时候提示：

  1. Downloading Dart SDK from Flutter engine 9bfa4f53cdbec57b0c3badc47bc13da145816c8d...
  2. Unknown operating system. Cannot install Dart SDK.

解决方案: 到 flutter 的 bin 目录下执行：

  1. flutter.bat doctor

如果是网络问题，导致无法下载Dart，可以手动到镜像站或GitHub下载最新的Dart安装包，手动解压到Flutter安装路径下的 bin/cache/dart-sdk 下。

Error connecting to the service protocol

错误详情：

  1. Error connecting to the service protocol: failed to connect to http://127.0.0.1:58820

或者错误如下：

  1. Error connecting to the service protocol: HttpException: Connection closed before full header was received

模拟器的Android版本太高，我的是Android Q，降为Android 9就正常了。

This is taking an unexpectedly long time

错误详情：

  1. (This is taking an unexpectedly long time.)

很大概率是Gradle下载太慢，手动下载zip包，将其复制到Gradle对应版本的文件夹。再次运行 flutter run 即可，Gradle会自动解压。
image.png

Waiting for another flutter command to release the startup lock…

解决办法：

  1. 打开任务管理器，看看有没有Dart.exe运行着，有的话全部结束了，然后重启试试
  2. 还是不行的话就删除掉flutter SDK中 bin\cache 目录下的 lockfile 文件

flutter_swiper 的问题

错误信息：

  1. ══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
  2. I/flutter (21956): The following assertion was thrown building NotificationListener:
  3. I/flutter (21956): ScrollController not attached to any scroll views.
  4. I/flutter (21956): 'package:flutter/src/widgets/scroll_controller.dart': Failed assertion: line 110 pos 12:
  5. I/flutter (21956): '_positions.isNotEmpty'
  6. I/flutter (21956):
  7. I/flutter (21956): Either the assertion indicates an error in the framework itself, or we should provide substantially

解决方案: 给 flutter_swiper 设置 key: ValueKey(items.length)

  1. Swiper(
  2.   key: ValueKey(carouselList.length),
  3.   itemBuilder: (BuildContext context,int index){
  4.     return new Image.network(carouselList[index],fit: BoxFit.fill,);
  5.   },
  6.   itemCount: carouselList.length,
  7.   pagination: new SwiperPagination(),
  8. ),

参考: swiper item can’t be hot add?

Entry point isn’t within current project

解决方式：在 Android Studio 中找到 File -> Project Structure -> Module 然后添加项目的根文件夹，然后它将再次检测到它是一个flutter的应用程序，然后再次构建和工作。

参考: Flutter 集成到Android项目中遇到的坑

MediaQuery.of() called with a context that does not contain a MediaQuery

解决方案：想让界面跑起来，需要 runApp()，需要再写个 MyApp() 里面使用 MaterialApp() 包裹写好的界面，这样才可以运行。

参考: Flutter: MediaQuery.of() called with a context that does not contain a MediaQuery

参考资料