JLabelの文字揃え

概要

JLabelで、左右中央両端などの文字揃えをテストします。

Screenshot

Download

• Runnable JAR example.jar
• Source code src.zip
• Repository GitHub

サンプルコード

JLabel l0 = new JLabel("打率");
JLabel l1 = new JLabel("打率", SwingConstants.RIGHT);
JLabel l2 = new JustifiedLabel("打率");
JLabel l3 = new JLabel("出塁率", SwingConstants.CENTER);
JLabel l4 = new JustifiedLabel("出塁率");
JLabel l5 = new JustifiedLabel("チーム出塁率");
// ...
class JustifiedLabel extends JLabel {
  private GlyphVector gvtext;
  private int prevWidth = -1;

  public JustifiedLabel() {
    this(null);
  }

  public JustifiedLabel(String str) {
    super(str);
  }

  @Override public void setText(String text) {
    super.setText(text);
    prevWidth = -1;
  }

  @Override protected void paintComponent(Graphics g) {
    Graphics2D g2 = (Graphics2D) g.create();
    Insets ins = getInsets();
    int w = getSize().width - ins.left - ins.right;
    if (w != prevWidth) {
      gvtext = getJustifiedGlyphVector(
          w, getText(), getFont(), g2.getFontRenderContext());
      prevWidth = w;
    }
    if (Objects.nonNull(gvtext)) {
      g2.setPaint(getBackground());
      g2.fillRect(0, 0, getWidth(), getHeight());
      g2.setPaint(getForeground());
      g2.drawGlyphVector(gvtext, ins.left, ins.top + getFont().getSize());
    } else {
      super.paintComponent(g);
    }
    g2.dispose();
  }

  private GlyphVector getJustifiedGlyphVector(
      int width, String str, Font font, FontRenderContext frc) {
    GlyphVector gv = font.createGlyphVector(frc, str);
    Rectangle2D r = gv.getVisualBounds();
    float jwidth = (float) width;
    float vwidth = (float) r.getWidth();
    if (jwidth > vwidth) {
      int num = gv.getNumGlyphs();
      float xx = (jwidth - vwidth) / (float) (num - 1);
      float xpos = num == 1 ? (jwidth - vwidth) * .5f : 0f;
      Point2D gmPos = new Point2D.Double(0d, 0d);
      for (int i = 0; i < num; i++) {
        GlyphMetrics gm = gv.getGlyphMetrics(i);
        gmPos.setLocation(xpos, 0);
        gv.setGlyphPosition(i, gmPos);
        xpos += gm.getAdvance() + xx;
      }
      return gv;
    }
    return null;
  }
}

解説

• JLabelの文字揃えは左揃え(デフォルトはSwingConstants.LEADING, ComponentOrientation.LEFT_TO_RIGHTでSwingConstants.LEFT)、右揃え(SwingConstants.TRAILING, ComponentOrientation.LEFT_TO_RIGHTでSwingConstants.RIGHT)、中央揃え(SwingConstants.CENTER)が設定可能
• JLabelの文字揃えに両端揃え(文字の均等割り付け)は存在しないので、上記のサンプルではJustifiedLabelを独自に作成
  • 幅が足りない場合は通常のJLabelと同様に...で省略

• JTextPaneに挿入、一文字の場合などのテスト

import java.awt.*;
import java.awt.font.*;
import java.awt.geom.*;
import javax.swing.*;

public class JustifiedLabelDemo {
  public JComponent makeUI() {
    String s = "\u2605";
    JTextPane textPane = new JTextPane();
    textPane.insertComponent(new JustifiedLabel(s));
    textPane.replaceSelection(": 111\n");
    textPane.insertComponent(new JustifiedLabel(s + s));
    textPane.replaceSelection(": 2222222\n");
    textPane.insertComponent(new JustifiedLabel(s + s + s));
    textPane.replaceSelection(": 3333\n");
    textPane.insertComponent(new JustifiedLabel(s + s + s + s));
    textPane.replaceSelection(": 4444444\n");
    textPane.insertComponent(new JustifiedLabel(s + s + s + s + s));
    textPane.replaceSelection(": 555\n");
    return new JScrollPane(textPane);
  }

  public static void main(String[] args) {
    EventQueue.invokeLater(JustifiedLabelDemo::createAndShowGui);
  }

  public static void createAndShowGui() {
    UIManager.put("swing.boldMetal", Boolean.FALSE);
    JFrame f = new JFrame();
    f.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
    f.getContentPane().add(new JustifiedLabelDemo().makeUI());
    f.setSize(320, 240);
    f.setLocationRelativeTo(null);
    f.setVisible(true);
  }
}

class JustifiedLabel extends JLabel {
  private GlyphVector gvText;
  private int prevWidth = -1;

  public JustifiedLabel() {
    this(null);
  }

  public JustifiedLabel(String str) {
    super(str);
    Dimension d = getPreferredSize();
    int baseline = getBaseline(d.width, d.height);
    setAlignmentY(baseline / (float) d.height);
  }

  @Override public Dimension getMinimumSize() {
    return getPreferredSize();
  }

  @Override public Dimension getPreferredSize() {
    Dimension d = super.getPreferredSize();
    d.width = getWidth();
    return d;
  }

  @Override public int getWidth() {
    return 120;
  }

  @Override protected void paintComponent(Graphics g) {
    Graphics2D g2 = (Graphics2D) g;
    Insets i = getInsets();
    int w = getWidth() - i.left - i.right;
    if (w != prevWidth) {
      gvText = getJustifiedGlyphVector(getText(), getFont(), g2.getFontRenderContext());
      prevWidth = w;
    }
    if (gvText != null) {
      g2.drawGlyphVector(gvText, i.left, i.top + getFont().getSize2D());
    } else {
      super.paintComponent(g);
    }
  }

  private GlyphVector getJustifiedGlyphVector(String str, Font font, FontRenderContext frc) {
    GlyphVector gv = font.createGlyphVector(frc, str);
    Rectangle2D r = gv.getVisualBounds();
    float width = (float) getWidth();
    float viewWidth = (float) r.getWidth();
    if (width < viewWidth) return null;
    int num = gv.getNumGlyphs();
    float xx = (width - viewWidth) / (float) (num - 1);
    float xpos = num == 1 ? (width - viewWidth) * .5f : 0f;
    Point2D gmPos = new Point2D.Double(0d, 0d);
    if (num == 1) System.out.println(gmPos);
    for (int i = 0; i < num; i++) {
      GlyphMetrics gm = gv.getGlyphMetrics(i);
      gmPos.setLocation(xpos, 0);
      gv.setGlyphPosition(i, gmPos);
      xpos += gm.getAdvance() + xx;
    }
    return gv;
  }
}

参考リンク

• JTableのセル内文字列を両端揃えにする
  • TextLayoutTextLayout#getJustifiedLayout(float) (Java Platform SE 8)メソッドを使用してJTableのセルで両端揃えを行うサンプル

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