Flutter is Google’s UI toolkit for building beautiful, natively compiled applications for mobile, web, and desktop from a single codebase.
由于国内的原因，需要设置环境变量
export PUB_HOSTED_URL=https://pub.flutter-io.cn
export FLUTTER_STORAGE_BASE_URL=https://storage.flutter-io.cn
进行诊断：flutter doctor
连接模拟器，运行项目：flutter run
