代码无误，为什么Menu菜单显示不了

activity.java
package your.mypackage.namespace;import android.app.Activity;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;public class WangActivity extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
    }
        public boolean onCreatOptionMenu(Menu menu)
        {
         super.onCreateOptionsMenu(menu);
         menu.add(0,0,0,R.string.app_about);
         menu.add(0,1,0,R.string.str_exit);
         return true;
        }
        
        public boolean onOptionsItemSelected(MenuItem item)
        {
         super.onOptionsItemSelected(item);
         switch(item.getItemId())
         {
         case 0:
         openOptionDialog();
             break;
         case 1:
         finish();
         break;
             }
         return true;
        }
        
        private void openOptionDialog()
        {
         new AlertDialog.Builder(this)
         .setTitle(R.string.app_about)
         .setMessage(R.string.app_about_msg)
         .setPositiveButton(R.string.str_ok,
         new DialogInterface.OnClickListener()
                 {
    public void onClick(DialogInterface dialog, int which) 
{

}
}
         )
.show();
        }
    }
main.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:background="@+drawable/white"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >
    
    <TextView 
     android:layout_width="fill_parent" 
     android:layout_height="wrap_content" 
     android:text="@string/hello"/>
</LinearLayout>