Question

我使用以下代码段创建Chatlog。

     chatlog = new JEditorPane("text/html", "<html>") {
        private static final long serialVersionUID = 1L;

        protected void paintComponent(Graphics g) {
            // set background green - but can draw image here too
            g.setColor(new Color(0,0,0,0));
            g.fillRect(0, 0, getWidth(), getHeight());

            // uncomment the following to draw an image
            Image img;
            try {
                img = ImageIO.read(new File("images/chatlog.png"));
                g.drawImage(img, 0, 0, this);
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

            super.paintComponent(g);
        }
    };

    chatlog.setFont(new Font("Segoe UI", Font.PLAIN, 14));
    chatlog.setEditable(false);
    chatlog.setOpaque(false);

    chatScroll = new JScrollPane(chatlog);
    chatScroll.setBounds(4, 454, 620, 100);
    chatScroll.setOpaque(false);
    chatScroll.setBackground(new Color(0,0,0,0));
    chatScroll.setBorder(BorderFactory.createEmptyBorder());
    chatScroll.setVisible(false);

就像你看到的那样，我在JEditorPane上使用背景图像。但是，如果我将大量内容写入Chatlog，背景图像会随文本向上移动。

你能帮帮我吗？

Answer 1

在标准HTML中，我们将使用background-attachment: scroll; CSS属性强制BG随着用户滚动页面向下滚动。黄色点作为背景放在样式中，以显示Swing如何不实现该属性。

另一方面，宽的黑色短图像由滚动窗格本身绘制，因此出现在我们想要绘制它的任何地方。

enter image description here

import java.awt.*;
import java.awt.image.BufferedImage;
import javax.swing.*;
import javax.swing.border.EmptyBorder;

public class BackgroundImageInHTML {

    // the GUI as seen by the user (without frame)
    private JPanel gui;
    private final static String HTML = "<html>"
            + "<head>"
            + "<style type=text/css>"
            + "body {"
            + "  background-image: http://i.stack.imgur.com/IHARa.png;"
            + "  background-repeat:no-repeat;"
            + "  background-position:left top;"
            + "  background-attachment: scroll;"
            + "  color: #BBBBBB;"
            + "}"
            + "</style>"
            + "</head>"
            + "<body>"
            + "<h1>Heading 1</h1>";
    private final String PARAGRAPH = "Lorem ipsum dolor sit amet, consectetur adipiscing elit. Aenean eu nulla urna. Donec sit amet risus nisl, a porta enim. Quisque luctus, ligula eu scelerisque gravida, tellus quam vestibulum urna, ut aliquet sapien purus sed erat. Pellentesque consequat vehicula magna, eu aliquam magna interdum porttitor. Class aptent taciti sociosqu ad litora torquent per conubia nostra, per inceptos himenaeos. Sed sollicitudin sapien non leo tempus lobortis. Morbi semper auctor ipsum, a semper quam elementum a. Aliquam eget sem metus.";

    BackgroundImageInHTML() {
        initializGui();
    }

    public void initializGui() {
        gui = new JPanel(new BorderLayout());
        gui.setBorder(new EmptyBorder(5, 5, 5, 5));
        // TODO - not ideal
        gui.setPreferredSize(new Dimension(400, 100));

        StringBuilder sb = new StringBuilder();
        sb.append(HTML);
        for (int ii = 0; ii < 10; ii++) {
            sb.append("<h2>Header 2</h2>");
            sb.append(PARAGRAPH);
        }
        JEditorPane jep = new JEditorPane();
        jep.setOpaque(false);
        jep.setContentType("text/html");
        jep.setText(sb.toString());
        JScrollPane jsp = new JScrollPane(jep) {
            BufferedImage bg = new BufferedImage(350,50,BufferedImage.TYPE_INT_RGB);
            @Override
            public void paintComponent(Graphics g) {
                super.paintComponent(g);
                g.drawImage(bg, 0, 0, this);
            }
        };
        jsp.getViewport().setOpaque(false);
        gui.add(jsp);
    }

    public JComponent getGui() {
        return gui;
    }

    public static void main(String[] args) {
        Runnable r = new Runnable() {

            @Override
            public void run() {

                BackgroundImageInHTML bih = new BackgroundImageInHTML();

                JFrame f = new JFrame("Demo");
                f.add(bih.getGui());
                // Ensures JVM closes after frame(s) closed and
                // all non-daemon threads are finished
                f.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
                // See http://stackoverflow.com/a/7143398/418556 for demo.
                f.setLocationByPlatform(true);

                // ensures the frame is the minimum size it needs to be
                // in order display the components within it
                f.pack();
                // should be done last, to avoid flickering, moving,
                // resizing artifacts.
                f.setVisible(true);
            }
        };
        // Swing GUIs should be created and updated on the EDT
        // http://docs.oracle.com/javase/tutorial/uiswing/concurrency
        SwingUtilities.invokeLater(r);
    }
}

JScrollPane中的JEditorPane，带有修复背景图像

1 个答案: