Question

如果您只是使用new Font("Arial", Font.PLAIN, 10)创建字体，稍后，当您尝试以该字体显示缺少的字形时，您将获得指示缺少字形的熟悉方块。

很久以前，我们找到了解决方法 - 将字体传递给FontUtilities.getCompositeFontUIResource(Font)，然后返回Font来处理字体本身不属于的字符的后备。

问题是，该实用程序在sun.font中，我想消除编译器警告。

鉴于在此期间已经过去多年，现在是否有适当的方法来做到这一点？

演示：

import java.awt.Font;
import java.awt.GridLayout;

import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.SwingUtilities;

import sun.font.FontUtilities;

public class TestFonts implements Runnable
{
    @Override
    public void run()
    {
        Font font = new Font("Arial", Font.PLAIN, 20);

        JLabel label1 = new JLabel("Before \u30C6\u30B9\u30C8");
        label1.setFont(font);

        JLabel label2 = new JLabel("After \u30C6\u30B9\u30C8");
        label2.setFont(FontUtilities.getCompositeFontUIResource(font));

        JFrame frame = new JFrame("Font Test");
        frame.setLayout(new GridLayout(2, 1));
        frame.add(label1);
        frame.add(label2);
        frame.pack();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }

    public static void main(String[] args)
    {
        SwingUtilities.invokeLater(new TestFonts());
    }
}

结果：

Answer 1

您可以利用JComponents能够显示HTML的事实，并通过将这些字符放在<span>中来覆盖JComponent的字体无法显示的字体的字体：

import java.util.Formatter;

import java.awt.Font;
import java.awt.GridLayout;

import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.SwingUtilities;

import sun.font.FontUtilities;

public class TestFonts implements Runnable
{
    /**
     * Replaces plain text meant to be displayed in a JComponent with
     * HTML that forces the font to Dialog for any characters which the
     * specified font cannot natively display.
     *
     * @param originalText text to transform to HTML, with forced fonts
     *                     where needed
     * @param font default font which will be used to display text
     *
     * @return HTML version of original text, which forces fonts where
     *         necessary to ensure all characters will be displayed
     */
    static String toCompositeFontText(String originalText,
                                      Font font) {
        Formatter html = new Formatter();
        html.format("%s", "<html><body style='white-space: nowrap'>");

        boolean fontOverride = false;
        int len = originalText.length();
        for (int i = 0; i < len; i = originalText.offsetByCodePoints(i, 1)) {
            int c = originalText.codePointAt(i);

            if (font.canDisplay(c)) {
                if (fontOverride) {
                    html.format("%s", "</span>");
                    fontOverride = false;
                }
            } else {
                if (!fontOverride) {
                    html.format("<span style='font-family: \"%s\"'>",
                        Font.DIALOG);
                    fontOverride = true;
                }
            }

            if (c == '<' || c == '>' || c == '&' || c < 32 || c >= 127) {
                html.format("&#%d;", c);
            } else {
                html.format("%c", c);
            }
        }

        if (fontOverride) {
            html.format("%s", "</span>");
        }

        html.format("%s", "</body></html>");

        return html.toString();
    }

    /**
     * Replaces text of the specified JLabel with HTML that contains the
     * same text, but forcing the font to Dialog for any characters which
     * the JLabel's current font cannot display.
     *
     * @param label JLabel whose text will be adjusted and replaced
     */
    static void adjustText(JLabel label) {
        label.setText(toCompositeFontText(label.getText(), label.getFont()));
    }

    @Override
    public void run()
    {
        Font font = new Font("Arial", Font.PLAIN, 20);

        JLabel label1 = new JLabel("Before \u30C6\u30B9\u30C8");
        label1.setFont(font);

        JLabel label2 = new JLabel("After \u30C6\u30B9\u30C8");
        label2.setFont(FontUtilities.getCompositeFontUIResource(font));

        JLabel label3 = new JLabel("Corrected \u30C6\u30B9\u30C8");
        label3.setFont(font);
        adjustText(label3);

        JFrame frame = new JFrame("Font Test");
        frame.setLayout(new GridLayout(3, 1));
        frame.add(label1);
        frame.add(label2);
        frame.add(label3);
        frame.pack();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }

    public static void main(String[] args)
    {
        SwingUtilities.invokeLater(new TestFonts());
    }
}

<强>更新

此外，您可以监控标签的text属性，以便自动执行此操作：

label.addPropertyChangeListener("text", new PropertyChangeListener() {
    @Override
    public void propertyChange(PropertyChangeEvent event) {
        String text = (String) event.getNewValue();
        if (text != null && !text.startsWith("<html>")) {
            adjustText((JLabel) event.getSource());
        }
    }
});

明显的缺点是没有（简单）方法来调整已经以<html>开头的文本。（实际上我很确定即使可以通过将标签的文本加载为HTMLDocument来完成。）

Answer 2

在深入挖掘JDK源代码之后，我发现了一个直接调用内部方法的公共方法。我不知道这是多么狡猾，但它至少是公共API。：）

        label2.setFont(StyleContext.getDefaultStyleContext()
            .getFont(familyName, style, size));

是否有非专有的等效于FontUtilities.getCompositeFontUIResource（Font）？

2 个答案: