I am new to custom renderers and can only do basic things like customizing entries, pickers etc. I am really trying to implement an android toolbar menu into my navbar on x.forms and I know I will need to do this through a custom renderer.

I just really do not know where to start. It has proven difficult to find what I need online so I am hoping someone could point me in the right direction. 

What I want is something that looks like this:
[![enter image description here](https://i.stack.imgur.com/JZC5I.png)](https://i.stack.imgur.com/JZC5I.png)

Which simply drops down and presents a list of options. Thanks in advance.