Question

我在点击框架时尝试制作，它会显示点击点的坐标。我这样做了：

public void mouseClicked(MouseEvent e) {

    int x = e.getX();
    int y = e.getY();
    j1.setLocation(x, y);
    j1.setText("(" + x  + ", " +  y + ")");


}

public void mousePressed(MouseEvent e) {
    int x = e.getX();
    int y = e.getY();
    j1.setLocation(x, y);
    j1.setText("(" + x  + ", " +  y + ")");



}
public void mouseDragged(MouseEvent e) {}
public void mouseMoved(MouseEvent e) {}
public void mouseEntered(MouseEvent e) {}
public void mouseExited(MouseEvent e) {}
public void mouseReleased(MouseEvent e) {}

但是当我点击它时，首先在中心显示坐标，然后是点击点，2次。但我只想要一个和点击点。我在哪里弄错了，我该怎么办？

Answer 1

只需使用mousePressed就可以了。当您单击鼠标时，通常会调用3种方法 - mousePressed，mouseReleased，如果鼠标在按下和释放之间不移动，则mouseClicked。您只想响应其中一种方法。

所以改为：

public void mouseClicked(MouseEvent e) {} // leave this empty

public void mousePressed(MouseEvent e) {
    int x = e.getX();
    int y = e.getY();
    j1.setLocation(x, y);
    j1.setText("(" + x  + ", " +  y + ")");

    // also be sure to tell your container to re-position components
    revalidate();
    repaint();
}

作为一个侧面建议，请注意，不是让一个类实现MouseListener，而是可以让它扩展MouseAdapter，这样你的类就不必拥有所有那些空的MouseListener接口方法。

例如：

import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import javax.swing.*;

@SuppressWarnings("serial")
public class MousePosition extends JPanel {
    private static final int PREF_W = 600;
    private static final int PREF_H = PREF_W;
    // format String for display String
    protected static final String FORMAT = "(%d, %d)";
    private int xPos = -40;
    private int yPos = -40;
    private String displayText = "";

    public MousePosition() {
        addMouseListener(new MouseAdapter() {
            @Override
            public void mousePressed(MouseEvent e) {
                xPos = e.getX();
                yPos = e.getY();
                // use FORMAT String to create our display text
                displayText = String.format(FORMAT, xPos, yPos);
                repaint();
            }
        });
    }

    @Override
    public Dimension getPreferredSize() {
        if (isPreferredSizeSet()) {
            return super.getPreferredSize();
        }
        return new Dimension(PREF_W, PREF_H);
    }

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        g.drawString(displayText, xPos, yPos);

    }

    private static void createAndShowGui() {
        MousePosition mainPanel = new MousePosition();

        JFrame frame = new JFrame("MousePosition");
        frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
        frame.getContentPane().add(mainPanel);
        frame.pack();
        frame.setLocationByPlatform(true);
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                createAndShowGui();
            }
        });
    }
}

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