When you own a device from the fruity manufacturers from Cupertino, you do not get the privilege of transferring files between devices other than using AirDrop. Technically, AirDrop is a combination of using Bluetooth and WiFi Direct to drag and drop files between Apple devices. While Android devices can plainly use Bluetooth to share files, WiFi Direct between devices have been a little finicky from one Android device to another. So we are stuck to using slow Bluetooth file transfers if you use an Android device from Xiaomi and I am using one from Samsung.
Of course WiFi Direct is an option, but only if you use certain smartphones that are from the same manufacturer. This may no longer be the case though. Fast file transfers between Android devices could be made possible with the “Peer-to-Peer Transmission Alliance”. The Alliance is made to allow high-speed file transfer and sharing between devices. In that case, you get AirDrop like performance from Android devices; 20MB/S over-the-air file transfer speeds.
The only issue is that the Alliance currently consists of three manufacturers. The three manufacturers are OPPO, Vivo, and Xiaomi. Not even HUAWEI is part of that alliance, which also means that you only get fast file transfers between these three manufacturers until anyone else joins the Alliance. Still, nothing wrong with being hopeful.
Source: Android Central, Mi Blog