I'd like to ask you about tools related to Android UX/UI.

I recommend Proto.io. The Android Material prototype has the advantage of being relatively well managed, simple, shared, or accessible, and has the disadvantage of being a little flustered by using the web-based operation.

Proto.io website

These days, it is becoming a fixed-term license model rather than a one-time license purchase, so it will not be easy to find such a tool in the future, but after searching a little, I think I can recommend two more.

I just looked it up on the Rabbit and found an article recommending http://pencil.evolus.vn/. I haven't used it myself, but there are often evaluation articles on the web, and it doesn't look bad. Besides, it's free. You can go to the link below, install the file according to the guide, and apply the Android stencil. https://github.com/nathanielw/Android-Lollipop-Pencil-Stencils https://github.com/nathanielw/Material-Icons-for-Pencil

And if you're looking for a nearly wireframe-like screen configuration rather than a feature-rich prototype, and if you're looking for a license-buying tool, you might as well use Sketch (http://bohemiancoding.com/sketch/). It's a design tool, but it's easy to use, so even developers can use it easily. It would be nice to install a sketch and use it after receiving Android template.