R cannot be resolved R file not found-Android error

I just downloaded and installed the latest Android SDK and I want to create a simple engineering study.

The code created according to the wizard is as follows

Package Eu.mauriziopz.gps;import Android.app.activity;import Android.os.bundle;public class Ggps extends Activity {    /** Called when the activity is first created. *    /@Override public    void OnCreate (Bundle savedinstancestate) {        super.oncreate (savedinstancestate);        Setcontentview (R.layout.main);    }}

Eclipse Error
R cannot be resolved, R file not found
Error line
Setcontentview (R.layout.main);
What's the reason?
I'm in res/layout/. There is a XML file named Main.xml

Processing methods

This is a mistake. It happened to me when I created a branch with the Eclipse Wizard New Andorid Project, it error ' R cannot be resolved '. I have to comment out the Setcontentview & Getmenuinflater lines, and then eclipse automatically generates the R.java file after I can uncomment the Setcontentview & Getmenuinflater lines.

Original address: http://www.itmmd.com/201410/36.html
This article by Meng Meng's IT person to organize the release, reprint must indicate the source.

R cannot be resolved R file not found-Android error