同一类的 java Graphics2d 实例的行为不同

Question

对于 Java 新手，我不明白为什么以下代码适用于我添加到表单中的第一个按钮，而不适用于同一类中的其他两个实例。另外， mouseExit 处理程序似乎根本没有被调用，或者只有在退出所有按钮时才被调用，而不是单独退出每个按钮。你能帮我吗？

设置是我有一个测试用例，其中包含一个简单的 JFrame、一个 contentPane 和一个带有显示钢琴键盘图标的 JLabel。就是这样。我创建了代表键的多边形按钮的实例，它们应该做的就是当鼠标经过它们时高亮显示，第一个按钮和其他按钮在文本中执行，但不在图形中执行 - 这意味着调用了正确的处理程序，但没有绘制完成了。

package com.mst.buttons;

import java.awt.BorderLayout;

public class buttonFrame extends JFrame {

    private JPanel contentPane;

    /**
     * Launch the application.
     */
    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                try {
                    buttonFrame frame = new buttonFrame();
                    frame.setVisible(true);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }

    /**
     * Create the frame.
     */
    public buttonFrame() {
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setBounds(100, 100, 578, 373);
        contentPane = new JPanel();
        contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
        setContentPane(contentPane);
        GridBagLayout gbl_contentPane = new GridBagLayout();
        gbl_contentPane.columnWidths = new int[]{0, 0, 0, 0, 0, 0, 0, 0};
        gbl_contentPane.rowHeights = new int[]{0, 0, 0, 0, 0};
        gbl_contentPane.columnWeights = new double[]{0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 1.0, Double.MIN_VALUE};
        gbl_contentPane.rowWeights = new double[]{0.0, 0.0, 0.0, 1.0, Double.MIN_VALUE};
        contentPane.setLayout(gbl_contentPane);

        JLabel piano = new JLabel("");
        piano.setLabelFor(piano);
        piano.setIcon(new ImageIcon("C:\\Users\\Donald\\workspace2\\Keyboard450x220.png"));
        GridBagConstraints gbc_piano = new GridBagConstraints();
        gbc_piano.insets = new Insets(0, 0, 5, 5);
        gbc_piano.fill = GridBagConstraints.BOTH;
        gbc_piano.gridx = 2;
        gbc_piano.gridy = 1;
        contentPane.add(piano, gbc_piano);

        ////////////////////////////////////////////////
        int[] xs1 = new int[] { 0,45,45,0,0 };
        int[] ys1 = new int[] { 0,0,220,220,0 };
        Polygon p1 = new Polygon(xs1, ys1, xs1.length);
        String n1 = "C3";

        int[] xs2 = new int[] { 45,90,90,45,45 };
        int[] ys2 = new int[] { 0,0,220,220,0 };
        Polygon p2 = new Polygon(xs2, ys2, xs2.length);
        String n2 = "D3";

        int[] xs3 = new int[] { 90,135,135,90,90 };
        int[] ys3 = new int[] { 0,0,220,220,0 };
        Polygon p3 = new Polygon(xs3, ys3, xs3.length);
        String n3 = "D3";

        PianoButton pb1 = new PianoButton(p1, n1);
        piano.add(pb1);

        PianoButton pb2 = new PianoButton(p2, n2);
        piano.add(pb2);

        PianoButton pb3 = new PianoButton(p3, n3);
        piano.add(pb3);
    }
}


class PianoButton extends JComponent implements MouseListener {

    Polygon key;
    String noteName;
    Color color;

    public PianoButton(Polygon p, String nn) {
        key = p;
        noteName = nn;
        color = Color.white;

        setBounds(key.getBounds());
        addMouseListener(this);
    }

    @Override
    public void mouseClicked(MouseEvent arg0) {}

    @Override
    public void mouseEntered(MouseEvent arg0) {
        hilite();
    }

    @Override
    public void mouseExited(MouseEvent arg0) {
        unhilite();
    }

    @Override
    public void mousePressed(MouseEvent arg0) {}

    @Override
    public void mouseReleased(MouseEvent arg0) {
        turnRed();
        repaint();
    }

    void hilite() {
        System.out.println("Turned yellow");
        color = Color.yellow;
        repaint();
    }

    void turnRed() {
        System.out.println("Turned Red");
        color = Color.red;
    }

    void unhilite() {
        System.out.println("Turned white");
        color = Color.white;
    }

    public void paintComponent(Graphics g){
        Graphics2D g2 = (Graphics2D) g;
        super.paintComponent(g2);
        g2.setColor(color);
        g2.fillPolygon(key);
        g2.drawPolygon(key);
    }
}

Answer 1

不要使用setBounds。问题似乎是代码将三个组件添加到标签。将它们添加到面板中。