Android studio generated automatically variable by an internal property m

 First click on the upper left corner of the File → setting   

 

 

Click Editor → Code Style → java

 

 

Click Code Generation → Name prefix (prefix)
Field, m (ordinary member variable prefix plus m my awareness of)
Static Field, S (static member variable prefix plus the consciousness s self)

 

 

 Finally, do not forget to click apply and ok.