重绘（）方法并非通过一个调用漆（）＆的paintComponent（）方法中的一种，只的paintC

我的应用程序可以裁剪图像。我想实现的是根据从MouseListeners拍摄的坐标削减图像之前绘制的矩形。这是我的代码：

public class ImageScreenShot extends JPanel implements MouseListener, MouseMotionListener {

    ImagePanel im;

    int drag_status = 0, c1, c2, c3, c4;

    public int getC1() {
        return c1;
    }

    public int getC2() {
        return c2;
    }

    public int getC3() {
        return c3;
    }

    public int getC4() {
        return c4;
    }

    public void cut() {
        im = new ImagePanel();
        GraphicalUserInterface.getFrame().add(im);
        im.addMouseMotionListener(this);
        im.addMouseListener(this);
    }

    public void draggedScreen() throws Exception {
        int w = c1 - c3;
        int h = c2 - c4;
        w = w * -1;
        h = h * -1;
        Robot robot = new Robot();
        BufferedImage img = robot.createScreenCapture(new Rectangle(c1, c2, w, h));
        File save_path = new File("screen1.jpg");
        ImageIO.write(img, "JPG", save_path);
        GraphicalUserInterface.getLabelIcon().setIcon(new ImageIcon(new ImageIcon(img).getImage().getScaledInstance(img.getWidth(),img.getHeight(),Image.SCALE_SMOOTH)));
        JOptionPane.showConfirmDialog(null,"Would you like to save your cropped Pic?");
        if(JOptionPane.YES_OPTION == 0){
            PicChanges.getCurrentLabel();
        } else {
            PicChanges.getCurrentLabel();

        }
        System.out.println("Cropped image saved successfully.");
    }

    @Override
    public void mouseClicked(MouseEvent arg0) {
    }

    @Override
    public void mouseEntered(MouseEvent arg0) {
    }

    @Override
    public void mouseExited(MouseEvent arg0) {
    }

    @Override
    public void mousePressed(MouseEvent arg0) {
        repaint();
        c1 = arg0.getXOnScreen();
        c2 = arg0.getYOnScreen();
    }

    @Override
    public void mouseReleased(MouseEvent arg0) {
        repaint();
        if (drag_status == 1) {
            c3 = arg0.getXOnScreen();
            c4 = arg0.getYOnScreen();
            try {
                this.repaint();
                draggedScreen();
            } catch (Exception e) {
                e.printStackTrace();
            }
        } else {
            System.out.println("Issue is under construction");
        }
    }

    @Override
    public void mouseDragged(MouseEvent arg0) {
        repaint();
        drag_status = 1;
        c3 = arg0.getXOnScreen();
        c4 = arg0.getYOnScreen();
    }

    @Override
    public void mouseMoved(MouseEvent arg0) {
    }

    @Override
    public void paint(Graphics g) {
        super.paint(g);
        int w = c1 - c3;
        int h = c2 - c4;
        w = w * -1;
        h = h * -1;
        if (w < 0)
            w = w * -1;
        g.setColor(Color.RED);
        g.drawRect(c1, c2, w, h);
        System.out.println("paint component");

    }
}

public class ImagePanel extends JPanel {
    private BufferedImage imageToCut;

    public ImagePanel() {
        Dimension size = new 
        Dimension(GraphicalUserInterface.getLabelIcon().getSize());
        setPreferredSize(size);
        setMaximumSize(size);
        setMinimumSize(size);
        setSize(size);
    }

    @Override
    protected void paintComponent(Graphics g) {
        g.drawImage(imageToCut, 0, 0, null);
        System.out.println("painted");
    }
}

我很困惑，我无法弄清楚如何调用paint()方法，这就是为什么截至目前，图像被裁切并正确，但矩形被绘制。据我了解我paintComponent()方法工作，我调用ImagePanel类，并添加MouseListeners它在repaint()方法被调用。

要调用paint()方法，我需要调用ImageScreenShot类，但这里的问题出现在哪里。

所以我的问题是，如何调用paint()被调用的方法repaint()方法在MouseListeners的ImageScreenShot类？

Answer 1:

我没有测试你的代码，但我一眼就可以看出：

你扩展JPanel ，这很好，但你要覆盖paint(...)方法，你不应该这样做，你需要重写paintComponent(...)
关于你的第二类，你要覆盖paintComponent(...)但你不打电话
```
 super.paintComponent(g); 
```
其中，更是打破了油漆链。而且很可能（与第一点）是你错误的原因。
见我应避免使用一套（首选|最大|最小）大小的Java Swing的方法呢？（是的），你需要重写getPreferredSize()并调用pack()在您的应用程序。

Answer 2:

使用arg0.getComponent().repaint(); 其中， arg0是的MouseEvent。这将重绘该事件被触发的组件。见https://docs.oracle.com/javase/8/docs/api/java/awt/event/ComponentEvent.html#getComponent--