There should be a gml4gtk graph viewer for android running on smatrphone or tablet

the google android courses at multiple levels are here at
https://developer.android.com/courses

The cordova software is recommended and can also be used for simple programs and offline use
https://cordova.apache.org/

Example of big and complete android app source with hosting of apk files is k9 mail at
https://github.com/k9mail/k-9

Make android app debuggable script
https://github.com/julKali/makeDebuggable