here is the problem:

Error:(7, 17) Resource id cannot be an empty string (at 'id' with value '@+id/').
Error:Execution failed for task ':app:processDebugResources'.
> com.android.ide.common.process.ProcessException: org.gradle.process.internal.ExecException: Process 'command 'C:\Users\User\AppData\Local\Android\sdk\build-tools\21.1.2\aapt.exe'' finished with non-zero exit value 1
Information:BUILD FAILED
Information:Total time: 15.409 secs
Information:2 errors
Information:0 warnings
Information:See complete output in console