Today, in an experiment of time, it has been an error occurs R can not be resolved to a variable, as shown below
Sorry, map is too big, then the problem has been bothering me, that first prompted to import the package is useless, then go online to check the information, found their R.java seemed to lack something, then I deleted after out R.java, save, and then clean the new gen, found the problem solved, although this solution is simple, but has troubled me for a long time, hope to be useful.