How to implement resizable fragment size using custom drag and drop (not predefined transitional animation)

Question

I'm not sure how to explain this better, but it is mainly implemented by chat applications for fragments of the gallery selection and so on. The best example is Google Allo, for which I posted a GIF below. I would like to know how this is implemented and how I can replicate this function.

As you can see, the first transition of the animation map fragment is from the bottom to half the screen, but then you can drag it to the top of the screen with your finger, when it actually fills the entire screen and even creates its own toolbar. Most of all I tested it, and it also works on API 16.