java - 小程序绘画

Question

我正在尝试获取绘图部分中的光标点并简单地绘制一个椭圆形。但运气不好!

public void paint(Graphics g){
     Point ComponentPoint = PaintPanel.getLocationOnScreen();
     Point CursorPoint=   MouseInfo.getPointerInfo().getLocation(); //gets cursor point

     int ComPX =  ComponentPoint.x;
     int ComPY =  ComponentPoint.y;
     int CurPX =  CursorPoint.x;
     int CurPY =  CursorPoint.y;
     int FinalX = CurPX - ComPX;
     int FinalY =  CurPY - ComPY;
     g.drawOval(FinalX, FinalY, 20, 20);
}

private void PaintPanelMouseDragged(java.awt.event.MouseEvent evt) {                                        
    //when mouse is moved over paintpanel

    //PaintPanel.repaint();
    not working
}             

这是没有paint方法的图像:

/image/VOyhr.png

Answer 1

您不能在 Paint 方法中添加这样的代码。您不会在paint 方法中引用MouseInfo 类，因为您无法控制何时调用paint() 方法。您应该使用 MouseListener 和 MouseMotionListner 来进行自定义绘画。另外，自定义绘画不应该在paint方法中完成。

参见Custom Painting Approaches两种解决方案。