I am learning how to use Ionic by doing a test application but I have had this problem for two days. I have looked for possible solutions but none has worked for me.
Inside android folder under platforms folder there is a file called project.properties Try replacing + with 27.1.0 in below lines
cordova.system.library.1=com.android.support:support-v4:+
cordova.system.library.2=com.android.support:appcompat-v7:+
Also do the same thing in build.gradle file
"com.android.support:support-v4:+"
"com.android.support:appcompat-v7:+"