Question

现在我正试着这样做，每当我点击我画的椭圆形内部时，拖动鼠标它会通过重新绘制来移动位置。但是，即使正确检测到MouseEvents，椭圆形图像也不会更新。我很困惑为什么会这样。以下是处理椭圆形，MouseEvents和更新的代码：

public class DrawOval extends JPanel {
private int size = 50;
private int locX = 0; //vector points
private int locY = 0;
private boolean isPressed = false;
private Shape oval = new Ellipse2D.Double(locX, locY, size, size * 2);

public DrawOval(int size){
    this.size = size;
    Dimension dims = new Dimension(size, size);
    setPreferredSize(dims);
    setMaximumSize(dims);
    setMinimumSize(dims);

    MouseAdapter m = new MouseAdapter(){
        public void mouseReleased(MouseEvent e){
            isPressed = false;
            update(e);
            System.out.println("Mouse is released!");
        }

        public void mousePressed(MouseEvent e){
            isPressed = true;
            update(e);
            System.out.println("Mouse is pressed!");
        }

        public void mouseDragged(MouseEvent e){
            if(isPressed){
                update(e);
                System.out.println("Mouse is dragged!");
            }
        }

        public void update(MouseEvent e){
            System.out.println("X: " + e.getX() + ", Y: " + e.getY());
            if(oval.contains(e.getX(), e.getY())){
                setX(e.getX()); setY(e.getY());
                repaint();
            }
            //does not update if the mouses click coordinates are outside of the oval
        }
    };
    addMouseListener(m); //for pressing and releasing
    addMouseMotionListener(m); //for dragging
}

public void setX(int _x){
    this.locX = _x;
}
public void setY(int _y){
    this.locY = _y;
}

public void paintComponent(Graphics g){
    super.paintComponent(g);
    Graphics2D g2 = (Graphics2D) g;
    g2.setColor(Color.BLACK);
    g2.fill(oval);
}
}

我无法弄清楚为什么它没有正确更新。之前我有部分工作，但它会一直更新，即使用户点击的位置不在椭圆内。

Answer 1

我认为您正在setX和setY忘记更新x中的y和oval。您至少有三个选择：

1）每次更改Ellipse2D.Double和this.locX时都会重新this.locY。

2）希望您的oval一劳永逸地创建x=0, y=0，检查鼠标事件切换到相对坐标（if(oval.contains(e.getX() - locX, e.getY() - locY)){...}）并使用{绘制oval {1}} AffineTransform。

3）将椭圆声明为g2.transform(...)，然后您可以直接更改其Ellipse2D.Double oval = new Ellipse2D.Double(...);和x，因为它们是公开的：

面板在Java中没有正确重新绘制图像？

1 个答案: