You need to override here, won't work if just add it to your viewport.
So create a folder "override" in your app folder and in it a folder "viewport".
Then put the above code in an Android.js file and adjust the app namespace:
Ext.define('App.override.viewport.Android', {

Then add 'myApp.override.viewport.Android' in the requires array in your app.js file.

You can add a alert message in the doFix method to make sure it's called on your Android device.