i am new to android i open a new project i try to run it but it cant run because it says that R file is not created .i did not do anything to the project which i opened here . please help me to run this .
and also i got a sample project when i try to run that also it cant be run because it says that R file cannot be created also.
please what should i do to solve this help me please. and also i want to know that what is R file in it i try to edit that but it says R file cannot be modify why is that going on so