MouseClicked 侦听器不适用于 gui

Question

我创建了这个获取鼠标坐标的程序，现在我想添加一个 mouseClicked，它在按下鼠标时在特定坐标处创建一个矩形。但它不起作用。这是我的代码：

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;


@SuppressWarnings("serial")
public class GameSetup extends JPanel implements MouseMotionListener {

public static JFrame njf = new JFrame("Test");
public static int x = 0, y = 0;
public static boolean c = false;
public static void main(String[] args) {

    GameSetup gs = new GameSetup();
    gs.addMouseMotionListener(gs);
    njf.add(gs);
    njf.setVisible(true);

}

public void paintComponent(Graphics g) {
    super.paintComponent(g);

    this.setBackground(Color.BLACK);

    g.setColor(Color.GREEN);
    g.drawRect(150, 75, 200, 100);
    g.setColor(Color.ORANGE);
    g.drawString("Play", 239, 123);


    if (x > 150 && y > 75 && x < 350 && y < 175){
        g.drawRect(150, 75, 200, 100);
    } 
    if(x > 150 && y > 75 && x < 350 && y < 175 && c){
        g.fillRect(10 , 10 ,100 ,100);
    }
}

public GameSetup() {

    super();
    setSize(500, 500);
    njf.setSize(500,500);
    njf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    njf.setResizable(false);
    njf.setLocationRelativeTo(null);

}

@Override
public void mouseDragged(MouseEvent arg0) {

}

@Override
public void mouseMoved(MouseEvent e) {
    x = e.getX();
    y = e.getY();
    if (x > 0 && y > 0) repaint(); else repaint();
}
public void mouseClicked(MouseEvent ea){
    c = true;
}
}

我怎样才能完成这项工作？谢谢

Answer 1

你总不能把 @Override 放在 mouseClicked(...) 上面吧？那是因为您的 class 没有实现正确的接口：MouseListener。也实现此接口，将对象也添加为 MouseListener，您将有权访问 MouseListener 事件。还可以考虑使用您的侦听器方法进行 repaint() 调用，以便 GUI 在必要时重新绘制自身。

我自己的偏好是不让我的视图 classes 也实现我的监听器接口，所以如果这是我的程序，我会创建一个内部 class 扩展 MouseAdapter 并将其用作 MouseListener 和 MouseMotionListener。

其他问题：

不要在绘画方法中调用setBackground。而是在构造函数中调用它。
尽可能避免 "magic" 个数字。
考虑使用 JLabel 或 JButton 来完成这项工作，因为您通常最好使用更高级别的构造以便于调试和增强。

例如没有 JLabel...

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Rectangle;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;

import javax.swing.*;


@SuppressWarnings("serial")
public class GameSetup2 extends JPanel {
    private static final int PREF_W = 500;
    private static final int PREF_H = PREF_W;
    private static final Color BG = Color.BLACK;
    private static final Color PASSIVE_COLOR = Color.GREEN;
    private static final Color ACTIVE_COLOR = Color.ORANGE;
    private static final String PLAY = "Play";
    private static final int PLAY_X = 239;
    private static final int PLAY_Y = 123;
    private Rectangle rectangle = new Rectangle(150, 75, 200, 100);
    private Color rectColor = PASSIVE_COLOR;
    private Color playColor = PASSIVE_COLOR;

    public GameSetup2() {
        setBackground(BG);
        MyMouse myMouse = new MyMouse();
        addMouseListener(myMouse);
        addMouseMotionListener(myMouse);
        // TODO Auto-generated constructor stub
    }

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D) g;
        g2.setColor(playColor);
        g2.drawString(PLAY, PLAY_X, PLAY_Y);
        g2.setColor(rectColor);
        g2.draw(rectangle);
    }

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

    private class MyMouse extends MouseAdapter {
        @Override
        public void mouseMoved(MouseEvent e) {
            if (rectangle.contains(e.getPoint())) {
                rectColor = ACTIVE_COLOR;
            } else {
                rectColor = PASSIVE_COLOR;
            }
            repaint();
        }

        @Override
        public void mousePressed(MouseEvent e) {
            if (rectangle.contains(e.getPoint())) {
                playColor = ACTIVE_COLOR;
            } 
            repaint();
        }

        public void mouseReleased(MouseEvent e) {
            playColor = PASSIVE_COLOR;
            repaint();
        };
    }

    private static void createAndShowGui() {
        GameSetup2 mainPanel = new GameSetup2();

        JFrame frame = new JFrame("GameSetup2");
        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(() -> createAndShowGui());
    }
}

Answer 2

为了配合 Hovercraft Full Of Eels 所说的内容，我进行了一些重构。注意：

实现 MouseListener 或扩展 MouseAdapter，并注册监听器 (addMouseListener)
变量不需要是 public 或静态的 -- 尝试最小化范围，使用更多封装作为最佳实践
添加 repaint() 对 mouseClicked 的调用
将 c 更改为 clicked 并使其在 true 和 false 之间切换，因此您可以看到它的变化

试试这个：

public class Game {

    public static void main(String[] args) {

        final JFrame frame = new JFrame("Test");
        frame.setSize(500, 500);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setResizable(false);
        frame.setLocationRelativeTo(null);
        frame.add(new GamePanel());
        frame.setVisible(true);

    }

    @SuppressWarnings("serial")
    private static class GamePanel extends JPanel {

        private int x = 0;
        private int y = 0;
        private boolean clicked = false;

        public GamePanel() {
            super();
            setSize(500, 500);
            setBackground(Color.BLACK);
            addMouseListener(new MouseListenerImpl());
            addMouseMotionListener(new MouseMotionListenerImpl());
        }

        @Override
        public void paintComponent(Graphics g) {
            super.paintComponent(g);

            g.setColor(Color.GREEN);
            g.drawRect(150, 75, 200, 100);
            g.setColor(Color.ORANGE);
            g.drawString("Play", 239, 123);

            if (x > 150 && y > 75 && x < 350 && y < 175) {
                g.drawRect(150, 75, 200, 100);
                if (clicked) {
                    g.fillRect(10, 10, 100, 100);
                }
            }
        }

        private class MouseListenerImpl extends MouseAdapter {
            @Override
            public void mouseClicked(MouseEvent e) {
                clicked = !clicked;
                repaint();
            }
        }

        private class MouseMotionListenerImpl extends MouseMotionAdapter {
            @Override
            public void mouseMoved(MouseEvent e) {
                x = e.getX();
                y = e.getY();
                repaint();
            }
        }
    }
}

MouseClicked 侦听器不适用于 gui

MouseClicked listener not working with gui

java

graphics

event-handling

mouseevent

mouselistener