JFrame上的MouseListener永远不会被调用

Question

我正在尝试使用MouseListener来查看何时在我的JFrame中单击了某些东西，但是从未调用过任何事件（mouseClicked，mouseEntered等）。我正在使用Canvas将游戏绘制到JFrame上，我想知道是否可能是这个问题，但是我不确定如何修复它。我正在关注this教程，我的代码看起来几乎完全相同。

这是我的JFrame类：

public class Display extends JFrame implements MouseListener {
    public static int width;
    public static int height;

    public static final int CARD_SIZE = 100;
    public static final int BUFFER_SIZE = 25;
    public static final int TITLE_SIZE = 50;

    private JFrame frame;
    private MyCanvas canvas;

    public Display (int r, int c, Card[][] b) {
        width = c*CARD_SIZE + (c+2)*BUFFER_SIZE;
        System.out.println(width);
        height = r*CARD_SIZE + (r+1)*BUFFER_SIZE + TITLE_SIZE*2;
        System.out.println(height);
        frame = new JFrame("Matching Game");
        frame.setLayout(null);
        frame.setSize(width, height);
        frame.setResizable(false);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setFocusable(true);

        frame.addMouseListener(this);

        canvas = new MyCanvas(b);
        frame.add(canvas);
        frame.setVisible(true);
    }

    @Override
    public void mouseClicked(MouseEvent e) {
        System.out.println("Mouse Clicked at X: " + e.getX() + " - Y: " + e.getY());
    }
    @Override
    public void mouseEntered(MouseEvent e) {
        System.out.println("Mouse Entered frame at X: " + e.getX() + " - Y: " + e.getY());
    }
    @Override
    public void mouseExited(MouseEvent e) {
        System.out.println("Mouse Exited frame at X: " + e.getX() + " - Y: " + e.getY());
    }
    @Override
    public void mousePressed(MouseEvent e) {
        System.out.println("Mouse Pressed at X: " + e.getX() + " - Y: " + e.getY());
    }
    @Override
    public void mouseReleased(MouseEvent e) {
        System.out.println("Mouse Released at X: " + e.getX() + " - Y: " + e.getY());
    }
}

Answer 1

您做错的主要事情是扩展JFrame并创建一个显式实例。请按照以下步骤操作。

import java.awt.Dimension;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;

import javax.swing.JFrame;
import javax.swing.JPanel;


public class Display  implements MouseListener {
    public static int width;
    public static int height;

    public static final int CARD_SIZE = 100;
    public static final int BUFFER_SIZE = 25;
    public static final int TITLE_SIZE = 50;

    private JPanel canvas;
    private JFrame frame;

    public static void main(String[] args) {
        new Display(3,3,new int[3][3]);

    }

    public Display (int r, int c, int[][] b) {
        width = c*CARD_SIZE + (c+2)*BUFFER_SIZE;
        System.out.println(width);
        height = r*CARD_SIZE + (r+1)*BUFFER_SIZE + TITLE_SIZE*2;
        System.out.println(height);
        frame = new JFrame("Matching Game");
//        frame.setLayout(null);
//        frame.setSize(width, height);
        frame.setResizable(false);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setFocusable(true);

        frame.addMouseListener(this);

        canvas = new JPanel();
        canvas.setPreferredSize(new Dimension(width,height));

        frame.add(canvas);
        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }

    @Override
    public void mouseClicked(MouseEvent e) {
        System.out.println("Mouse Clicked at X: " + e.getX() + " - Y: " + e.getY());
    }
    @Override
    public void mouseEntered(MouseEvent e) {
        System.out.println("Mouse Entered frame at X: " + e.getX() + " - Y: " + e.getY());
    }
    @Override
    public void mouseExited(MouseEvent e) {
        System.out.println("Mouse Exited frame at X: " + e.getX() + " - Y: " + e.getY());
    }
    @Override
    public void mousePressed(MouseEvent e) {
        System.out.println("Mouse Pressed at X: " + e.getX() + " - Y: " + e.getY());
    }
    @Override
    public void mouseReleased(MouseEvent e) {
        System.out.println("Mouse Released at X: " + e.getX() + " - Y: " + e.getY());
    }
}

要考虑的要点

• 不扩展JFrame，仅使用一个实例。
• 帆布很旧。我建议使用JPanel来容纳组件和/或绘画
• [frame.setLocationRelativeTo(null)]将框架在屏幕上居中。
• 因为我没有Card类，所以我使用int[][]对此进行了演示。
• 我做过的其他事情，请查阅API文档以获取解释。

有关GUI的更多信息，请查看Java Tutorials