JFrame 上的 MouseListener 从未被调用

Question

我正在尝试使用 MouseListener 来查看何时在我的 JFrame 中单击了某些内容，但是曾调用过 none 事件（mouseClicked、mouseEntered 等）。我正在使用 Canvas 将游戏绘制到 JFrame 上，我想知道这是否可能是问题所在，但我不确定如何修复它。我正在学习 this 教程，我的代码看起来几乎完全一样。

这是我的 JFrame class:

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 并创建一个的显式实例。如下操作。

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

不要扩展 JFrame，只使用一个实例。
Canvas老了。我推荐使用一个 JPanel 来保存组件 and/or painting
frame.setLocationRelativeTo(null) 您的框架在屏幕上居中。
因为我没有 Card class 我用 int[][] 来演示这个。
我所做的任何其他事情，请查看 API 文档以获取解释。

有关 GUI 等的更多信息，请查看 Java Tutorials

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