i was trying to follow this tutorial:
http://www.gdgankara.org/2012/11/01/step-by-step-android-development-with-maven/
but after setting up the environment,
I'm using macOS 10.14 and in my case: I download Android packaging tool from AAPT and then copied all the files into $ANDROID_HOME/platforms/$SDK/tools/
$ANDROID_HOME/platforms/$SDK/tools/
DON'T REMIND CHANGE $SDK WITH YOUR REAL NAME SDK FOR INSTANCE android-29