This is by far the easiest method I’ve used to transfer files between Android devices and a computer on the same WiFi network.
1. Download the WiFi File Explorer App to your Android device
2. Open the app on your Android device
3. The app will display a web url address (ex. http://192.168.1.114.6000)
4. Now type in that web url address on your computer in your web browser (Chrome, Firefox, etc)
5. It will now display all the files on your Android device (you can either download files to your computer, or upload files to the Android device)
6. Transfer away!
*note: for large files, you’ll probably still want to use a usb cable for faster transfers instead of this wireless method.