java 中的 setOpaque()

Question

谁能解释为什么 Nimbius 对待 setOpaque() 的方式与其他 java LaF 不同。它破坏了我的代码，因为通常透明的组件不再是透明的。

编辑：问题似乎只涉及 JTextAreas （这是我需要的）或类似的组件。

编辑编辑：这是实际应用程序的屏幕。当应用trashgod的解决方案时，背景仍然不显示。

编辑编辑编辑：
我尝试了trashgod的建议来覆盖paint()。我为此辛苦了几个小时，但无法让它发挥作用。我能够显示背景，但无法移动 JinternalFrame、调整其大小以及选择其文本。调用super.paint(g)未能解决该问题。有没有一种简单的方法可以做到这一点，我可能会错过？
我对此采取了一种新方法。 JInternalFrame 内部是一个 JLayeredPane。
第 0 层 - JLabel
第 1 层 - JTextArea

当 JInternalFrame 移动或调整大小时：

1. 使其自身不可见
2. 拍摄其在容器中所在位置的屏幕截图 用其拍摄的
3. 图像绘制 JLabel
4. 使其自身再次可见。

因为我根本无法让 JInternalFrame 变得透明。我模拟了它的透明度。唯一的问题是，与此相关的开销很大。有什么想法吗？

package newpackage;

import java.awt.Color;
import java.awt.Component;
import java.awt.Container;
import java.awt.Dimension;
import java.awt.Graphics2D;
import java.awt.Rectangle;
import java.awt.image.BufferedImage;
import javax.swing.ImageIcon;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JInternalFrame;
import javax.swing.JLayeredPane;
import javax.swing.JPanel;
import javax.swing.UIManager;

/**
 * Example of how to create a transparent internal frame.
 * @author dvargo
 */
public class TransparentInternalFrame extends JInternalFrame {

    JLayeredPane container;


    /**
     * Defualt constructor to set the frame up
     * @param container The container for the frame
     * @param opacity The opacity of the frame
     */
    public TransparentInternalFrame(JLayeredPane container, int opacity) {
        super("", true, true, true, true);
        this.container = container;
        initComponents();
        setSize(200, 200);
        putClientProperty("JInternalFrame.isPalette", Boolean.TRUE);
        scrollPane.setBackground(new Color(0, 0, 0, opacity));
        scrollPane.getViewport().setBackground(new Color(0, 0, 0, opacity));
        textArea.setBackground(new Color(0, 0, 0, opacity));
        setBG();
    }

    /**
     * Builds the GUI
     */
    private void initComponents() {

        layeredPane = new javax.swing.JLayeredPane();
        imageLabel = new javax.swing.JLabel();
        scrollPane = new javax.swing.JScrollPane();
        textArea = new javax.swing.JTextArea();

        imageLabel.setBounds(0, 0, 360, 260);
        layeredPane.add(imageLabel, javax.swing.JLayeredPane.DEFAULT_LAYER);

        scrollPane.setBorder(null);

        textArea.setColumns(20);
        textArea.setRows(5);
        textArea.addKeyListener(new java.awt.event.KeyAdapter() {

            public void keyPressed(java.awt.event.KeyEvent evt) {
                textAreaKeyPressed(evt);
            }

            public void keyReleased(java.awt.event.KeyEvent evt) {
                textAreaKeyReleased(evt);
            }

            public void keyTyped(java.awt.event.KeyEvent evt) {
                textAreaKeyTyped(evt);
            }
        });

        addComponentListener(new java.awt.event.ComponentAdapter() {

            public void componentMoved(java.awt.event.ComponentEvent evt) {
                frameMoved();
            }

            public void componentResized(java.awt.event.ComponentEvent evt) {
                frameResized();
            }
        });

        scrollPane.setViewportView(textArea);

        scrollPane.setBounds(0, 0, 360, 260);
        layeredPane.add(scrollPane, javax.swing.JLayeredPane.PALETTE_LAYER);



        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
       getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
                layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING).addComponent(layeredPane, javax.swing.GroupLayout.PREFERRED_SIZE, 362, javax.swing.GroupLayout.PREFERRED_SIZE));
        layout.setVerticalGroup(
              layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING).addComponent(layeredPane, javax.swing.GroupLayout.PREFERRED_SIZE, 261, javax.swing.GroupLayout.PREFERRED_SIZE));
    }

    /**
     * The text will be blurred with out this
     * @param evt
     */
    private void textAreaKeyTyped(java.awt.event.KeyEvent evt) {
        repaintAll();
    }

    /**
     * The text will be blurred with out this
     * @param evt
     */
    private void textAreaKeyPressed(java.awt.event.KeyEvent evt) {
        repaintAll();
    }

    /**
     * The text will be blurred with out this
     * @param evt
     */
    private void textAreaKeyReleased(java.awt.event.KeyEvent evt) {
        repaintAll();
    }

    /**
     * Capture whats behind the frame and paint it to the image label
     */
    private void setBG() {

        setVisible(false);
        Rectangle location = new Rectangle(this.getX() + container.getX(),
                this.getY() + container.getY(),
                (int) this.getSize().getWidth() + 8 + ((javax.swing.plaf.basic.BasicInternalFrameUI) getUI()).getNorthPane().getWidth(),
                (int) this.getSize().getHeight() + ((javax.swing.plaf.basic.BasicInternalFrameUI) getUI()).getNorthPane().getHeight() + 4);
        ImageIcon newIcon = new ImageIcon(createImage((JComponent) container, location));
        setVisible(true);
        imageLabel.setIcon(newIcon);
        repaint();
    }

    /**
     * Only need to update the image label if the frame is moved or resized
     */
    private void frameResized() {
        setBG();
        textArea.repaint();
    }

    /**
     * Only need to update the image label if the frame is moved or resized
     */
    private void frameMoved() {
        setBG();
        for(Component x : container.getComponents())
        {
            //see if its a jinternalframe
            if(x.getClass().getName().equals(this.getClass().getName()))
            {
                //cast it
                TransparentInternalFrame temp = (TransparentInternalFrame)x;
                //make sure its not the same one as this
                if(x.getBounds().equals(this.getBounds()))
                {
                    return;
                }
                //if they intersect
                if(x.getBounds().intersects(this.getBounds()))
                {
                    this.setVisible(false);
                    temp.setBG();
                    this.setVisible(true);
                }
            }
        }

        textArea.repaint();
    }

    private void repaintAll() {
        textArea.repaint();
        imageLabel.repaint();
        layeredPane.repaint();
        scrollPane.repaint();
        scrollPane.getViewport().repaint();
        textArea.repaint();
        repaint();
    }

    /**
     *  Create a BufferedImage for Swing components.
     *  All or part of the component can be captured to an image.
     *
     *  @param  component Swing component to create image from
     *  @param  region The region of the component to be captured to an image
     *  @return image the image for the given region
     */
    public static BufferedImage createImage(JComponent component, Rectangle region) {
        //  Make sure the component has a size and has been layed out.
        //  (necessary check for components not added to a realized frame)

        if (!component.isDisplayable()) {
            Dimension d = component.getSize();

            if (d.width == 0 || d.height == 0) {
                d = component.getPreferredSize();
                component.setSize(d);
            }

            layoutComponent(component);
        }

        BufferedImage image = new BufferedImage(region.width, region.height, BufferedImage.TYPE_INT_RGB);
        Graphics2D g2d = image.createGraphics();

        //  Paint a background for non-opaque components,
        //  otherwise the background will be black

        if (!component.isOpaque()) {
            g2d.setColor(component.getBackground());
            g2d.fillRect(region.x, region.y, region.width, region.height);
        }

        g2d.translate(-region.x, -region.y);
        component.paint(g2d);
        g2d.dispose();
        return image;
    }

    public static void layoutComponent(Component component) {
        synchronized (component.getTreeLock()) {
            component.doLayout();

            if (component instanceof Container) {
                for (Component child : ((Container) component).getComponents()) {
                    layoutComponent(child);
                }
            }
        }
    }
    private javax.swing.JLabel imageLabel;
    private javax.swing.JScrollPane scrollPane;
    private javax.swing.JLayeredPane layeredPane;
    private javax.swing.JTextArea textArea;


    public static void main(String args[])
    {
        try
        {
            UIManager.setLookAndFeel(
                "com.sun.java.swing.plaf.nimbus.NimbusLookAndFeel");
        }
        catch (Exception e)
        {
            e.printStackTrace();
        }

        JFrame container = new JFrame();
        container.setSize(800, 800);

        JLayeredPane layerPanel = new JLayeredPane();
        layerPanel.setSize(800, 800);
        container.getContentPane().add(layerPanel);
        layerPanel.setVisible(true);

        JPanel colorPanel = new JPanel();
        colorPanel.setSize(800,800);
        colorPanel.setBackground(Color.red);
        layerPanel.add(colorPanel);
        layerPanel.setLayer(colorPanel, JLayeredPane.DEFAULT_LAYER);

        TransparentInternalFrame frameA = new TransparentInternalFrame(layerPanel,0);
        frameA.setVisible(true);
        layerPanel.add(frameA);
        layerPanel.setLayer(frameA, 1);
        frameA.setSize(282,282);

        TransparentInternalFrame frameB = new TransparentInternalFrame(layerPanel, 0);
        frameB.setVisible(true);
        layerPanel.add(frameB);
        layerPanel.add(frameB,1);
        frameB.setLocation(300, 300);
        frameB.setSize(282,282);

        container.repaint();
        container.setVisible(true);

    }
}

Answer 1

您可能会从不透明度部分获得一些见解> 文章在 AWT 和 Swing 中绘画。特别是，设置 opaque 属性并不意味着“使组件的背景透明”。演示该问题的 sscce 也可能会富有成效。

附录：简化您的示例，看起来文本区域本身可以变得透明，但是 Nimbus 默认值正在影响该区域的边界。您可以尝试相应地更改它们。

关于代码的一些注意事项：

• 始终在事件调度线程上构建 GUI。
• 不要从另一个线程中绘制。
• 不要吞下异常。

附录：请参阅对 create() 的更改。

附录：您可能还想查看 isPalette 属性

jif.putClientProperty("JInternalFrame.isPalette", Boolean.TRUE);

import java.awt.Color;
import java.awt.EventQueue;
import java.awt.FlowLayout;
import javax.swing.JInternalFrame;
import java.awt.Font;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextArea;
import javax.swing.UIManager;

public class TransparentTextArea extends JTextArea {

    int alpha;

    public TransparentTextArea(int alpha) {
        super(4, 16);
        this.alpha = alpha;
        this.setBackground(new Color(0, 0, 0, alpha));
        this.setFont(new Font("Serif", Font.ITALIC, 24));
        this.setEditable(false);
        this.setText("Twas brillig and the slithy toves,\n"
            + "Did gyre and gimble in the wabe;\n"
            + "All mimsy were the borogoves,\n"
            + "And the mome raths outgrabe.");
    }

    private static void create() {
        JFrame f = new JFrame();
        f.setLayout(new FlowLayout());
        f.getContentPane().setBackground(new Color(0xffffc0));
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        JInternalFrame jif = new JInternalFrame();
        JPanel panel = new JPanel();
        panel.setBackground(new Color(0xffffc0));
        panel.add(new TransparentTextArea(0));
        jif.add(panel);
        jif.setVisible(true);

        f.add(jif);
        f.pack();
        f.setVisible(true);
    }

    public static void main(String[] args) {

        try {
            UIManager.setLookAndFeel(
                "com.sun.java.swing.plaf.nimbus.NimbusLookAndFeel");
        } catch (Exception e) {
            e.printStackTrace();
        }

        EventQueue.invokeLater(new Runnable() {

            @Override
            public void run() {
                create();
            }
        });
    }
}

Answer 2

正如此处所解释的，setOpaque 并不执行您认为它会执行的操作，并且Nimbus 中的失败是显而易见的。另一个涉及阿尔法颜色的答案是完成你想要的事情的正确方法。