findviewbyid:
findViewById(int id) is a method of the View and Activity classes. This method will take a resource Id usually in the form of R.id.mView and will return to you a View object that is a reference to that View. Note that the returned object will nearly always need to be cast to the correct type of View before you can start interacting with it. If a View by the given ID does not exist within the current activity or parent View then you will receive null.