run-android就会报这个错, 我的java版本是1.8.0_231, 模拟器是夜神. (在官网脚手架的demo中会自动打开as中的模拟器, 但是这里失效了)

[magicsli]

(node:7416) [DEP0022] DeprecationWarning: os.tmpDir() is deprecated. Use os.tmpdir() instead.
Starting JS server...
Running C:\Users\Administrator\AppData\Local\Android\Sdk/platform-tools/adb reverse tcp:8081 tcp:8081
adb.exe: error: no devices/emulators found
Could not run adb reverse: Command failed: C:\Users\Administrator\AppData\Local\Android\Sdk/platform-tools/adb reverse tcp:8081 tcp:8081
Building and installing the app on the device (cd android && gradlew.bat installDebug...

FAILURE: Build failed with an exception.

• What went wrong:
  Could not determine java version from '12.0.2'.

• Try:
  Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output.
  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