【新手】使用全局对象出现Source Not Found异常

package ray.global.centa;import android.app.Application;public class Screen extends Application {        public int Screen_Width;    public int Screen_Heigh;    }

package ray.app.centa;import android.app.Activity;import android.os.Bundle;import android.util.DisplayMetrics;public class CentaPhoneAppActivity extends Activity {    /** Called when the activity is first created. */    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.main);                ray.global.centa.Screen screen = (ray.global.centa.Screen)getApplicationContext();        DisplayMetrics dm = new DisplayMetrics();        getWindowManager().getDefaultDisplay().getMetrics(dm);                //screen.Screen_Width = dm.widthPixels;        //screen.Screen_Width = dm.heightPixels;    }}