When you compile an android project from its xml resource, Eclipse considers it as executing xml file and so you get some output from it, in the same name of the xml with .out.xml extension. And you’ll end up with an *.out.xml file and the error
res\layout\main.xml:0: error: Resource entry main is already defined.
To solve this, first delete the output file res/layout/*.out.xml that Eclipse created. Right click the project and select run as -> Android Application then do the following
Window -> Preferences -> Run/Debug -> Launching -> Launch Operation -> Always Launch the previously launched application
After this you can you can press “run” or “ctrl+f11” from even a xml file, your project will get executed.