how to Upload .hex file to Arduino Uno through Android USB

I want to create android app to upload .hex file to arduino uno via USB. Sketch IDE creates .hex file after compiling program .And able to upload to arduino uno via USB. So can any body tell me that how make android app to upload .hex file to arduno uno . There is app called “Arduino Commander” on google play store who can able upload using USB. And also I want to know android source code for that.