Two things are commonly recommended for Android-owning RPi users: one, tether with your smartphone instead of buying a separate Wifi dongle, and two, set up a VNC connection when you don’t have an HDMI setup handy.

To do both at the same time, however, is tricky – the tethering is typically done via DHCP to tell the Pi the gateway address, while VNC users like to give their Pi a static address so they don’t need to guess what to connect to.

As it turns out, you can have both: Android’s tethering IP is actually hardcoded to precisely 192.168.42.129. This means you can set up a static IP (like 192.168.42.42) and a fixed gateway address for internet access.

Without qualms and reservations, you can write into your /etc/network/interfaces:

iface usb0 inet static
gateway 192.168.42.129
Bonus: if you’ve set up your Pi via ethernet because there’s a laptop on your desk anyway and you’re tired of staring at a small screen, you can also share that laptop’s wifi through the ethernet cable while using VNC. In this case, there is no hardcoded address. Still, once you find out your computer’s IP you can use the route command to make it your Pi’s gateway, without having to edit the interfaces file and restarting anything:
sudo route add default gw <your_computer's_ip>