android development on options menu

I am new to Android development by using PhoneGap, I try to build an options menu through a tutorial from http://developer.android.com/guide/topics/ui/menus.html, but it always gave error messages like below:

[2011-12-20 16:45:28 - HelloPhoneGap] W/ResourceType(23444): Bad XML block: header size >84 or total size 0 is larger than data size 0 [2011-12-20 16:45:28 - HelloPhoneGap] C:..\workspace\HelloPhoneGap\res\menu\menu.xml:3: >error: Error: No resource found that matches the given name (at 'title' with value >'@string/new_game'). [2011-12-20 16:45:28 - HelloPhoneGap] C:..\workspace\HelloPhoneGap\res\menu\menu.xml:5: >error: Error: No resource found that matches the given name (at 'title' with value >'@string/help').

Here is console code:

package com.phonegap.helloworld;

import android.os.Bundle;
import com.phonegap.*;

public class App extends DroidGap {
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    super.loadUrl("file:///android_asset/www/jqm/index.htm");
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    MenuInflater inflater = getMenuInflater();
    inflater.inflate(R.menu.game_menu, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle item selection
    switch (item.getItemId()) {
    case R.id.new_game:
        newGame();
        return true;
    case R.id.help:
        showHelp();
        return true;
    default:
        return super.onOptionsItemSelected(item);
    }
}

@Override
public boolean onKeyDown(int keyCode,KeyEvent event){
        if (keyCode == KeyEvent.KEYCODE_MENU) {
           return false;
       }else{
           return super.onKeyDown(keyCode, event);
       }

}

}

menu.xml

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:id="@+id/new_game"
      android:title="@string/new_game" />
    <item android:id="@+id/help"
      android:title="@string/help" />
</menu>

Did anybody tell what cause the errors?

Thanks a lot!

---

After define string in string.xml, the error gone away but I've meet new errors like below

KeyEvent cannot be resolved to a type   App.java    /HelloPhoneGap/src/com/phonegap/helloworld  line 39 Java Problem
KeyEvent cannot be resolved to a variable   App.java    /HelloPhoneGap/src/com/phonegap/helloworld  line 40 Java Problem
Menu cannot be resolved to a type   App.java    /HelloPhoneGap/src/com/phonegap/helloworld  line 17 Java Problem
MenuInflater cannot be resolved to a type   App.java    /HelloPhoneGap/src/com/phonegap/helloworld  line 18 Java Problem
MenuItem cannot be resolved to a type   App.java    /HelloPhoneGap/src/com/phonegap/helloworld  line 24 Java Problem

you must have define Strings new_game in values like

<resources>
<string name="new_game">Your String</string>
 <string name="help">Your String</string>
</resources>

refer this

You can create values xml file -If you are using eclipse then right click on the project and select other and there select android xml file,then given window select resource type as value,