React Native : target with hash string 'android-X' not found

Question

I am trying to develop my first react-native Android app. When I run

sudo react-native run-android

I get the following error

Answer 1

I followed the React Native Getting Started instructions and my ANDROID_HOME and PATH was right but I was still getting this error.

The solution was to install "Android 6.0 (Marshmallow)" from this screen (without clicking "Show Package Details"):