Question

我想根据鼠标的x和y位置在屏幕上移动图像。每次单击鼠标时，图像应移动到该位置。

public class testSquare {
  public static void main(String[] args) throws Exception {
    //...
    //object that stores x and y of mouse click
    testSquareInfo obj = new testSquareInfo(0, 0);
    //...
    //panel that draws image, seems to only execute once
    JPanel p = new JPanel ()
    {
        protected void paintComponent(Graphics a){ 
            int x = obj.getXPos();
            int y = obj.getYPos(); 
            a.drawImage(img, x, y, 50, 50, null);
        }        
      };
    //listens for mouse click and sends x and y to object
    p.addMouseListener(new MouseAdapter() {
    @Override 
    public void mousePressed(MouseEvent e) {
        int xMouse = e.getX();
        int yMouse = e.getY(); 
        obj.changeX(xMouse);
        obj.changeY(yMouse); 

        System.out.println(xMouse+" "+yMouse);
    }
    }); 

    window.add(p);
    window.setVisible(true); 
  }  
 } 

//Second Class

public class testSquareInfo 
{
    private int x, y; 
    public testSquareInfo(int x, int y)
    {
       this.x = x;
       this.y = y;
    }
    public void changeX(int xNew)
    {
        x = xNew;
    }
    public void changeY(int yNew)
    {
        y = yNew;
    }
    public int getXPos()
    {
        return x;
    }
    public int getYPos()
    {
        return y;
    } 
}

运行代码后，由于x和y初始化为这些值，因此将图像绘制在窗口的0、0坐标处。在屏幕周围单击不会移动图像，但是会正确更新存储在对象中的x和y。在测试过程中的某一时刻，图像确实移到了屏幕上的其他位置。但是，这发生在我没有单击窗口并且此后无法复制它时。我不确定它何时或如何移动。谢谢，

Answer 1

将p.repaint();添加到您的mousePressed方法中。这将导致面板重新绘制。

但是，仅执行此操作只会将另一个Image添加到图形组件中。

如果您不想将图像保持在先前的位置，
在super.paintComponent(a);方法的开头添加一个paintComponent
以使面板处于空白状态。< / p>

JPanel p = new JPanel() {

    protected void paintComponent(Graphics a){ 

        super.paintComponent(a);

        int x = obj.getXPos();
        int y = obj.getYPos(); 
        a.drawImage(img, x, y, 50, 50, null);
    }        
  };

//listens for mouse click and sends x and y to object
p.addMouseListener(new MouseAdapter() {
    @Override 
    public void mousePressed(MouseEvent e) {
        int xMouse = e.getX();
        int yMouse = e.getY(); 
        obj.changeX(xMouse);
        obj.changeY(yMouse); 

        System.out.println(xMouse+" "+yMouse);
        p.repaint();
    }
});

Answer 2

更改了此内容：

 p.addMouseListener(new MouseAdapter() {
    @Override 
    public void mousePressed(MouseEvent e) {
        int xMouse = e.getX();
        int yMouse = e.getY(); 
        obj.changeX(xMouse);
        obj.changeY(yMouse); 

        System.out.println(xMouse+" "+yMouse);
    }
    });

为此：

 p.addMouseListener(new MouseAdapter() {
    @Override 
    public void mousePressed(MouseEvent e) {
        int xMouse = e.getX();
        int yMouse = e.getY(); 
        obj.changeX(xMouse);
        obj.changeY(yMouse); 
        p.repaint(); 
        System.out.println(xMouse+" "+yMouse);
    }
    });

有没有一种方法可以多次执行paintComponent（）中的代码？

2 个答案: