java环境配置

location of your Java installation.
error 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/getting-started.html
error Command failed: gradlew.bat app:installDebug. Run CLI with --verbose flag for more details.