java - 如何使 JSlider 背景透明？或如何在 JLayeredPane 中正确覆盖 JComponents？

Question

我正在尝试将 JSlider 覆盖在 JProgressBar 之上。我正在使用 JLayeredPane 来保存这两个组件。我将 JProgressBar 添加到 JLayeredPane，然后添加 JSlider。到目前为止，我已经尝试通过将 opaque 设置为 false 并覆盖 paintComponent 方法来使 JSlider 透明。我最终得到的是滑块手柄是唯一在背景保持不透明时变得透明的部分。我可能没有正确使用 JLayeredPane，但我对 JLabels 的测试似乎有效。如何让 JSlider 的背景透明？

JSlider slider = new JSlider()
{

    @Override
    public void paintComponent(java.awt.Graphics g)
    {
        java.awt.Graphics2D g2 = (java.awt.Graphics2D) g;
        g2.setComposite(AlphaComposite.getInstance(
                AlphaComposite.SRC_OVER, (float) 0.5));

        super.paintComponent(g2);
    }

};

感谢大家的帮助。通过您的示例，我发现我的问题出在我正在使用的 JLayeredPane 上。我认识到可以使 JSlider 背景透明，但是，我仍然无法让下面图层上的组件显示出来。这是我的例子：

public class SliderTest extends JFrame
{

private JPanel contentPane;

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

/**
 * Create the frame.
 */
public SliderTest()
{
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setBounds(100, 100, 450, 300);
    contentPane = new JPanel();
    contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
    contentPane.setLayout(new BorderLayout(0, 0));
    setContentPane(contentPane);

    JPanel panel = new JPanel();
    contentPane.add(panel, BorderLayout.CENTER);
    panel.setLayout(new BorderLayout(0, 0));

    JLayeredPane layeredPane = new JLayeredPane();

    panel.add(layeredPane, BorderLayout.CENTER);
    layeredPane.setLayout(new BorderLayout(0, 0));

    JProgressBar progressBar = new JProgressBar();
    progressBar.setValue(50);
    layeredPane.add(progressBar);
    layeredPane.setLayer(progressBar, 0);

    JSlider slider = new JSlider()
    {
        @Override
        protected void paintComponent(Graphics g)
        {
            Graphics2D g2d = (Graphics2D) g.create();
            g2d.setColor(getBackground());
            g2d.setComposite(AlphaComposite.SrcOver.derive(0.5f));
            g2d.fillRect(0, 0, getWidth(), getHeight());
            g2d.dispose();

            super.paintComponent(g);
        }

    };
    layeredPane.setLayer(slider, 1);
    slider.setOpaque(false);

    // layeredPane.setLayer(slider, 1);
    layeredPane.add(slider, BorderLayout.CENTER);

}

}

score 4 · Accepted Answer

这将取决于您想要实现的目标。默认情况下JSlider是透明的。

这里重要的是 opaque 属性必须是false，否则重绘管理器不会在组件后面绘制...

在此处输入图像描述

顶部滑块，透明背景（蓝色），不透明控件
中间滑块，透明背景（绿色），透明控件

底部滑块，正常JSlider

公共类TestSlider {

public static void main(String[] args) {
    new TestSlider();
}

public TestSlider() {
    EventQueue.invokeLater(new Runnable() {
        @Override
        public void run() {
            try {
                UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
            } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
            }

            JFrame frame = new JFrame("Test");
            frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            frame.setLayout(new BorderLayout());
            frame.add(new TestPane());
            frame.pack();
            frame.setLocationRelativeTo(null);
            frame.setVisible(true);
        }

    });
}

public class TestPane extends JPanel {

    public TestPane() {
        setBackground(Color.RED);

        setLayout(new GridBagLayout());
        GridBagConstraints gbc = new GridBagConstraints();
        gbc.gridwidth = GridBagConstraints.REMAINDER;
        gbc.fill = GridBagConstraints.HORIZONTAL;

        add(new TransparentBackgroundSlider(), gbc);
        add(new TransparentSlider(), gbc);
        add(new JSlider(), gbc);

    }

}

public class TransparentBackgroundSlider extends JSlider {

    public TransparentBackgroundSlider() {
        // Important, we taking over the filling of the
        // component...
        setOpaque(false);
        setBackground(Color.BLUE);
    }

    @Override
    protected void paintComponent(Graphics g) {
        Graphics2D g2d = (Graphics2D) g.create();
        g2d.setColor(getBackground());
        g2d.setComposite(AlphaComposite.SrcOver.derive(0.5f));
        g2d.fillRect(0, 0, getWidth(), getHeight());
        g2d.dispose();

        super.paintComponent(g);
    }

}

public class TransparentSlider extends JSlider {

    public TransparentSlider() {
        // Important, we taking over the filling of the
        // component...
        setOpaque(false);
        setBackground(Color.GREEN);
    }

    @Override
    public void paint(Graphics g) {
        Graphics2D g2d = (Graphics2D) g.create();
        g2d.setComposite(AlphaComposite.SrcOver.derive(0.5f));
        super.paint(g2d);
        g2d.dispose();
    }

    @Override
    protected void paintComponent(Graphics g) {
        // We need this because we've taken over the painting of the component
        Graphics2D g2d = (Graphics2D) g.create();
        g2d.setColor(getBackground());
        g2d.fillRect(0, 0, getWidth(), getHeight());
        g2d.dispose();

        super.paintComponent(g);
    }

}

}

更新图层示例

在此处输入图像描述

public class TestSlider {

    public static void main(String[] args) {
        new TestSlider();
    }

    public TestSlider() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                }

                JFrame frame = new JFrame("Test");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setLayout(new BorderLayout());
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }

        });
    }

    public class TestPane extends JLayeredPane {

        private JProgressBar pb;
        private JSlider slider;

        public TestPane() {

            pb = new JProgressBar();
            slider = new JSlider();

            add(pb, new Integer(0));
            add(slider, new Integer(1));

        }

        @Override
        public Dimension getPreferredSize() {
            Dimension size = pb.getPreferredSize();
            size.height *= 4;
            size.width = Math.max(size.width, slider.getPreferredSize().width);
            return size;
        }

        @Override
        public void doLayout() {
            super.doLayout();

            int width = getWidth();
            int height = getHeight();

            Dimension size = pb.getPreferredSize();

            int x = 10;
            int y = (getHeight() - size.height) / 2;

            pb.setLocation(x, y);
            size.width = getWidth() - 21;
            pb.setSize(size);

            size = slider.getPreferredSize();
            x = (getWidth() - size.width) / 2;
            y = (getHeight() - size.height) / 2;
            slider.setBounds(x, y, size.width, size.height);

        }

    }

}

java - 如何使 JSlider 背景透明？或如何在 JLayeredPane 中正确覆盖 JComponents？

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