eclipse - R cannot be resolved - Android error -

i downloaded , installed new android sdk. wanted create simple application test drive it.

the wizard created code:

package eu.mauriziopz.gps;  import android.app.activity; import android.os.bundle;  public class ggps extends activity {     /** called when activity first created. */     @override     public void oncreate(bundle savedinstancestate) {         super.oncreate(savedinstancestate);         setcontentview(r.layout.main);     } } 

but eclipse gives me error

r cannot resolved

on line

setcontentview(r.layout.main); 

why?

ps: have xml file named main.xml under res/layout/.

after tracking down problem well, found note in android documentation:

http://source.android.com/source/using-eclipse.html

*note: eclipse likes add "import android.r" statement @ top of files use resources, when ask eclipse sort or otherwise manage imports. cause make break. out these erroneous import statements , delete them.*

while going through android sample tutorials, use ctrl + shift + o command "organize imports" , generate missing import statements. generate incorrect import statement hide r.java class automatically generated when build.