JButton内に複数のJLabelをBorderLayoutで配置する

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概要

JLabelをBorderLayoutでJButton内に2つ配置したキーキャップを作成し、それをJPanel内にGridBagLayoutでテンキー状にレイアウトします。

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サンプルコード

private static JButton makeButton(String... s) {
  String key = s[0];
  String sub = s.length > 1 ? s[1] : " ";
  int gap = 2;
  Border border = BorderFactory.createEmptyBorder(gap, gap, gap, gap);
  JLabel l1 = new JLabel(key);
  l1.setFont(l1.getFont().deriveFont(12f));
  l1.setBorder(border);
  JLabel l2 = new JLabel(sub);
  l2.setFont(l2.getFont().deriveFont(9.5f));
  l2.setBorder(border);
  JButton button = new JButton() {
    @Override public void updateUI() {
      super.updateUI();
      setLayout(new BorderLayout());
      setMargin(border.getBorderInsets(this));
    }

    @Override public Dimension getPreferredSize() {
      int sz = SIZE - gap * 2;
      return new Dimension(sz, sz);
    }
  };
  if (Objects.equals(key, sub)) {
    button.add(l1);
  } else {
    button.add(l1, BorderLayout.NORTH);
    button.add(l2, BorderLayout.SOUTH);
  }
  return button;
}
View in GitHub: Java, Kotlin

解説

  • JButtonでキーキャップを作成
    • JButton#getPreferredSize()をオーバーライドして指定したサイズの正方形になるよう設定
    • 文字列やアイコンなしの空JButtonにBorderLayoutを設定
      • キーキャップの印字を2つのJLabelで別々に作成してJButton#add(..., BorderLayout.NORTH)、JButton#add(..., BorderLayout.SOUTH)でJButtonにレイアウト
  • JPanelにキーキャップを配置してテンキーを作成 
GridBagConstraints c = new GridBagConstraints();
c.insets = new Insets(1, 1, 1, 1);
c.fill = GridBagConstraints.BOTH;
c.gridx = 0;
c.gridy = 0;
JPanel panel = new JPanel(new GridBagLayout());
panel.add(makeButton("<html>Num<br>Lock"), c);
c.gridx = GridBagConstraints.RELATIVE;
panel.add(makeButton("/"), c);
panel.add(makeButton("*"), c);
panel.add(makeButton("-"), c);
c.gridx = 0;
c.gridy++;
panel.add(makeButton("7", "Home"), c);
c.gridx = GridBagConstraints.RELATIVE;
panel.add(makeButton("8", "↑"), c);
panel.add(makeButton("9", "PgUp"), c);
c.gridheight = 2;
panel.add(makeButton("+", "+"), c);
c.gridx = 0;
c.gridy++;
c.gridheight = 1;
panel.add(makeButton("4", "←"), c);
c.gridx = GridBagConstraints.RELATIVE;
panel.add(makeButton("5"), c);
panel.add(makeButton("6", "→"), c);
c.gridx = 0;
c.gridy++;
panel.add(makeButton("1", "End"), c);
c.gridx = GridBagConstraints.RELATIVE;
panel.add(makeButton("2", "↓"), c);
panel.add(makeButton("3", "PgDn"), c);
c.gridheight = 2;
JButton enter = makeButton("Enter", "Enter");
panel.add(enter, c);
EventQueue.invokeLater(() -> {
  getRootPane().setDefaultButton(enter);
  enter.requestFocusInWindow();
});
c.gridx = 0;
c.gridy++;
c.gridwidth = 2;
c.gridheight = 1;
panel.add(makeButton("0", "Insert"), c);
c.gridx = GridBagConstraints.RELATIVE;
c.gridwidth = 1;
panel.add(makeButton(".", "Delete"), c);
panel.setBorder(BorderFactory.createLineBorder(Color.WHITE));

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