Android gesture operation example (judgment of up/down/left/right)

public class GestureActivity extends Activity {
  private GestureDetector gestureDetector;
  private Screen screen;
  @Override
  public void onCreate(Bundle savedInstanceState) {
    (savedInstanceState);
    setContentView();
    gestureDetector = new GestureDetector(this,onGestureListener);
    //Get the screen size    screen = (this);
  }
  @Override
  public boolean onTouchEvent(MotionEvent event) {
    return (event);
  }
   onGestureListener = new (){
    @Override
    public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,
        float velocityY) {
      float x = () - ();
      float y = () - ();
      //The limit must be passed 1/3 of the screen to be considered as passing      float x_limit =  / 3;
      float y_limit =  / 3;
      float x_abs = (x);
      float y_abs = (y);
      if(x_abs >= y_abs){
        //gesture left or right
        if(x > x_limit || x < -x_limit){
          if(x>0){
            //right
            show("right");
          }else if(x
            //left
            show("left");
          }
        }
      }else{
        //gesture down or up
        if(y > y_limit || y < -y_limit){
          if(y>0){
            //down
            show("down");
          }else if(y
            //up
            show("up");
          }
        }
      }
      return true;
    }
  };
  private void show(String value){
    (this, value, Toast.LENGTH_SHORT).show();
  }
}

public class GestureUtils {
  //Get the screen size  public static Screen getScreenPix(Context context) {
    DisplayMetrics dm = new DisplayMetrics();
    WindowManager windowManager = (WindowManager) (Context.WINDOW_SERVICE);
    ().getMetrics(dm);
    return new Screen(,);
  }
  public static class Screen{
    public int widthPixels;
    public int heightPixels;
    public Screen(){
    }
    public Screen(int widthPixels,int heightPixels){
      =widthPixels;
      =heightPixels;
    }
    @Override
    public String toString() {
      return "("+widthPixels+","+heightPixels+")";
    }
  }
}