Error: Unable to open class file R.java

Solution:

The “Build Path” for your Java environment is not setup correctly in Eclipse. To fix this, follow these steps:

1) Open the Preferences Window by clicking Window -> Preferences

2) Find the Java section and expand it

3) Select Build Path

4) Change the value of Source and output folder from Folders to Project

5) Click Apply and then OK

Your problem should be resolved!