android: R cannot be resolved to a variable

I'm developing an android application for a month. and today when I cleaned my project (project>clean...), I got "R cannot be resolved to a variable" error and i can't run my app.

I Googled for solution and did ever开发者_StackOverflow社区y solution for this problem but not success.

Note: I removed all imports R and cleaned my project again but the problem exists.

Can anyone help me?

Sorry for bad English!

Edit: problem solved. there was some errors in one of xml files.

this appears when you have errors in layout files or other xml files. Also take care that images have names that don t contain upper caracters

I solved my problem

LinearLayout android:id="@id/TelNoLayout" 

replace to

LinearLayout android:id="@+id/TelNoLayout"

and build