Changing JTable header text alignment of specific columns

• download example.jar
• download src.zip
• repository

Code

JTable table2 = makeTable();
table2.getColumnModel().getColumn(0).setHeaderRenderer(
    new HorizontalAlignmentHeaderRenderer(SwingConstants.LEFT));
table2.getColumnModel().getColumn(1).setHeaderRenderer(
    new HorizontalAlignmentHeaderRenderer(SwingConstants.CENTER));
table2.getColumnModel().getColumn(2).setHeaderRenderer(
    new HorizontalAlignmentHeaderRenderer(SwingConstants.RIGHT));

//...
class HorizontalAlignmentHeaderRenderer implements TableCellRenderer {
  private int horizontalAlignment = SwingConstants.LEFT;
  public HorizontalAlignmentHeaderRenderer(int horizontalAlignment) {
    this.horizontalAlignment = horizontalAlignment;
  }
  @Override public Component getTableCellRendererComponent(
      JTable table, Object value, boolean isSelected,
      boolean hasFocus, int row, int column) {
    TableCellRenderer r = table.getTableHeader().getDefaultRenderer();
    JLabel l = (JLabel) r.getTableCellRendererComponent(
        table, value, isSelected, hasFocus, row, column);
    l.setHorizontalAlignment(horizontalAlignment);
    return l;
  }
}

References

• Changing JTable header text alignment of specific columns(Japanese)

Use an editable JComboBox as a TableCellEditor

• download example.jar
• download src.zip
• repository

Code

class ComboCellEditor extends AbstractCellEditor implements TableCellEditor {
  private final JComboBox<String> combo = new JComboBox<>();
  protected ComboCellEditor() {
    super();
    combo.setEditable(true);
    combo.addActionListener(e -> {
      fireEditingStopped();
    });
  }
  @Override public Component getTableCellEditorComponent(
      JTable table, Object value, boolean isSelected, int row, int column) {
    if (value instanceof ComboBoxModel) {
      @SuppressWarnings("unchecked")
      ComboBoxModel<String> m = (ComboBoxModel<String>) value;
      combo.setModel(m);
    }
    return combo;
  }
  @Override public Object getCellEditorValue() {
    @SuppressWarnings("unchecked")
    DefaultComboBoxModel<String> m = (DefaultComboBoxModel<String>) combo.getModel();
    if (combo.isEditable()) {
      String str = Objects.toString(combo.getEditor().getItem(), "");
      if (!str.isEmpty() && m.getIndexOf(str) < 0) {
        m.insertElementAt(str, 0);
        combo.setSelectedIndex(0);
      }
    }
    return m;
  }
}

References

• Use an editable JComboBox as a TableCellEditor(Japanese)

Select multiple JCheckBox in JComboBox

• download example.jar
• download src.zip
• repository

Code

class CheckedComboBox<E extends CheckableItem> extends JComboBox<E> {
  private boolean keepOpen;
  private transient ActionListener listener;

  protected CheckedComboBox() {
    super();
  }

  protected CheckedComboBox(ComboBoxModel<E> aModel) {
    super(aModel);
  }

  protected CheckedComboBox(E[] m) {
    super(m);
  }

  @Override public Dimension getPreferredSize() {
    return new Dimension(200, 20);
  }

  @Override public void updateUI() {
    setRenderer(null);
    removeActionListener(listener);
    super.updateUI();
    listener = e -> {
      if ((e.getModifiers() & AWTEvent.MOUSE_EVENT_MASK) != 0) {
        updateItem(getSelectedIndex());
        keepOpen = true;
      }
    };
    setRenderer(new CheckBoxCellRenderer<CheckableItem>());
    addActionListener(listener);
    getInputMap(JComponent.WHEN_FOCUSED).put(
        KeyStroke.getKeyStroke(KeyEvent.VK_SPACE, 0), "checkbox-select");
    getActionMap().put("checkbox-select", new AbstractAction() {
      @Override public void actionPerformed(ActionEvent e) {
        Accessible a = getAccessibleContext().getAccessibleChild(0);
        if (a instanceof BasicComboPopup) {
          BasicComboPopup pop = (BasicComboPopup) a;
          updateItem(pop.getList().getSelectedIndex());
        }
      }
    });
  }

  private void updateItem(int index) {
    if (isPopupVisible()) {
      E item = getItemAt(index);
      item.selected ^= true;
      setSelectedIndex(-1);
      setSelectedItem(item);
    }
  }

  @Override public void setPopupVisible(boolean v) {
    if (keepOpen) {
      keepOpen = false;
    } else {
      super.setPopupVisible(v);
    }
  }

  public static <E extends CheckableItem> String getCheckedItemString(
        ListModel<E> model) {
    return IntStream.range(0, model.getSize())
        .mapToObj(model::getElementAt)
        .filter(CheckableItem::isSelected)
        .map(Objects::toString)
        .sorted()
        .collect(Collectors.joining(", "));
  }
}

References

• Select multiple JCheckBox in JComboBox(Japanese)

Change the color of the label represents the current value of a JSlider

• download example.jar
• download src.zip
• repository

Code

slider.getModel().addChangeListener(new ChangeListener() {
  private int prev = -1;
  private void resetForeground(Object o, Color c) {
    if (o instanceof Component) {
      ((Component) o).setForeground(c);
    }
  }

  @Override public void stateChanged(ChangeEvent e) {
    BoundedRangeModel m = (BoundedRangeModel) e.getSource();
    int i = m.getValue();
    if ((slider.getMajorTickSpacing() == 0 ||
         i % slider.getMajorTickSpacing() == 0) && i != prev) {
      Dictionary dictionary = slider.getLabelTable();
      resetForeground(dictionary.get(i), Color.RED);
      resetForeground(dictionary.get(prev), Color.BLACK);
      slider.repaint();
      prev = i;
    }
  }
});

References

• Change the color of the label represents the current value of a JSlider(Japanese)

Keep visible the JPopupMenu while clicking on CheckBox

• download example.jar
• download src.zip
• repository

Code

JMenuItem mi = new JMenuItem(" ");
mi.setLayout(new BorderLayout());
mi.add(new JCheckBox(title) {
  private transient MouseAdapter handler;

  @Override public void updateUI() {
    removeMouseListener(handler);
    removeMouseMotionListener(handler);
    super.updateUI();
    handler = new DispatchParentHandler();
    addMouseListener(handler);
    addMouseMotionListener(handler);
    setFocusable(false);
    setOpaque(false);
  }
});
popup.add(mi);

popup.add(new JCheckBoxMenuItem("keeping open #2") {
  @Override public void updateUI() {
    super.updateUI();
    setUI(new BasicCheckBoxMenuItemUI() {
      @Override protected void doClick(MenuSelectionManager msm) {
        // super.doClick(msm);
        System.out.println("MenuSelectionManager: doClick");
        menuItem.doClick(0);
      }
    });
  }
});

// https://bugs.openjdk.java.net/browse/JDK-8165234
// Provide a way to not close toggle menu items on mouse click on component level
// JDK 9
JMenuItem menuItem = new JMenuItem("JMenuItem");
menuItem.putClientProperty("CheckBoxMenuItem.doNotCloseOnMouseClick", true);

References

• swing - How to prevent JPopUpMenu disappearing when checking checkboxes in it? - Stack Overflow
• Keep visible the JPopupMenu while clicking on CheckBox(Japanese)
• [JDK-8165234] Provide a way to not close toggle menu items on mouse click on component level - Java Bug System