When I'm doing 'react-native run-android' I'll have the following questions
Scanning folders for symlinks in S:\demoTest\node_modules (40ms) JS server already running. Building and installing the app on the device (cd android && gradlew.bat installDebug)...
Failure: Build failed with an exception.
What went wrong: A problem occurred configuring root project 'demoTest'.
Could not resolve all files for configuration ':classpath'. Could not resolve com.android.tools.build:gradle:3.1.2. Required by: project : Could not resolve com.android.tools.build:gradle:3.1.2. Could not get resource 'https://jcenter.bintray.com/com/android/tools/build/gradle/3.1.2/gradle-3.1.2.pom'. Could not GET 'https://jcenter.bintray.com/com/android/tools/build/gradle/3.1.2/gradle-3.1.2.pom'. Connect to 127.0.0.1:1087 [/127.0.0.1] failed: Connection refused: connect
Try: Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output.
Get more help at https://help.gradle.org
BUILD FAILED in 2s 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