Demo7不能运行。

[kingctan]

报错：
···
$ react-native run-android
Starting JS server...
Building and installing the app on the device (cd android && ./gradlew installDebug...
Could not install the app on the device, read the error above for details.
Make sure you have an Android emulator running or a device connected and have
set up your Android development environment:
https://facebook.github.io/react-native/docs/android-setup.html
···
本机环境运行其它RN项目没问题的。谢谢！