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package bjc.utils.gui.panels;
import javax.swing.*;
import javax.swing.border.EmptyBorder;
import java.awt.*;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
/**
* A JPanel with a clickable header that can collapse/expand its content.
*
* Features:
* - Title + arrow (▶ / ▼)
* - Optional custom header component on the right side (e.g., buttons, filters)
* - Add children like a normal JPanel (they go into the content area)
*/
public class CollapsiblePanel extends JPanel {
private static final long serialVersionUID = -5941733171067755926L;
private final JPanel headerPanel;
private final JPanel headerClickableArea;
private final JPanel headerExtrasPanel;
private final JButton toggleButton;
private final JLabel titleLabel;
private final JPanel contentPanel;
private boolean collapsed = false;
private boolean internalAdd = false; // guard for addImpl
/**
* Create a new collapsible panel.
*
* @param title The title for the panel
*/
public CollapsiblePanel(String title) {
this(title, new FlowLayout(FlowLayout.LEFT, 4, 4));
}
/**
* Create a new collapsible panel, using the following layout manager for the content.
*
* @param title The title for the panel
* @param contentLayout The layout manager for the panel
*/
public CollapsiblePanel(String title, LayoutManager contentLayout) {
super(new BorderLayout());
// === Header ===
headerPanel = new JPanel(new BorderLayout(4, 0));
headerPanel.setBorder(new EmptyBorder(2, 4, 2, 4));
headerPanel.setOpaque(false);
// Left side: clickable region (arrow + title)
headerClickableArea = new JPanel(new BorderLayout(4, 0));
headerClickableArea.setOpaque(false);
toggleButton = new JButton("\u25BC"); // ▼ expanded
toggleButton.setMargin(new Insets(0, 4, 0, 4));
toggleButton.setFocusable(false);
toggleButton.setBorderPainted(false);
toggleButton.setContentAreaFilled(false);
titleLabel = new JLabel(title);
titleLabel.setBorder(new EmptyBorder(0, 2, 0, 0));
titleLabel.setFont(titleLabel.getFont().deriveFont(Font.BOLD));
headerClickableArea.add(toggleButton, BorderLayout.WEST);
headerClickableArea.add(titleLabel, BorderLayout.CENTER);
// Right side: custom header component container
headerExtrasPanel = new JPanel(new FlowLayout(FlowLayout.RIGHT, 4, 0));
headerExtrasPanel.setOpaque(false);
headerPanel.add(headerClickableArea, BorderLayout.CENTER);
headerPanel.add(headerExtrasPanel, BorderLayout.EAST);
// === Content ===
contentPanel = new JPanel(contentLayout);
// === Wiring: toggle behavior ===
toggleButton.addActionListener(e -> setCollapsed(!isCollapsed()));
MouseAdapter headerClick = new MouseAdapter() {
@Override
public void mouseClicked(MouseEvent e) {
if (SwingUtilities.isLeftMouseButton(e)) {
setCollapsed(!isCollapsed());
}
}
};
// Only the left side (arrow + title) toggles; extras panel is not clickable for
// toggle
headerClickableArea.addMouseListener(headerClick);
titleLabel.addMouseListener(headerClick);
toggleButton.addMouseListener(headerClick);
// Add header + content to this panel
internalAdd = true;
add(headerPanel, BorderLayout.NORTH);
add(contentPanel, BorderLayout.CENTER);
internalAdd = false;
}
/**
* Returns the content panel; you can use this if you want direct access.
*
* @return The content panel
*/
public JPanel getContentPanel() {
return contentPanel;
}
/**
* Returns the panel that holds extra header components (right side).
*
* @return The header extras panel
*/
public JPanel getHeaderExtrasPanel() {
return headerExtrasPanel;
}
/**
* Replace any existing header extras with a single component. Pass null to
* clear.
*
* @param comp The header component to use
*/
public void setHeaderComponent(Component comp) {
headerExtrasPanel.removeAll();
if (comp != null) {
headerExtrasPanel.add(comp);
}
headerExtrasPanel.revalidate();
headerExtrasPanel.repaint();
}
/**
* Add an extra component to the header (right side) without clearing existing
* ones.
*
*
* @param comp The component to add
*/
public void addHeaderComponent(Component comp) {
headerExtrasPanel.add(comp);
headerExtrasPanel.revalidate();
headerExtrasPanel.repaint();
}
/**
* Set the header title text.
*
* @param title The header title
*/
public void setTitle(String title) {
titleLabel.setText(title);
}
/**
* Get the header title
*
* @return The header title
*/
public String getTitle() {
return titleLabel.getText();
}
/**
* Collapse or expand the content.
*
* @param collapsed True to collapse the panel, false to expand it
*/
public void setCollapsed(boolean collapsed) {
if (this.collapsed == collapsed)
return;
this.collapsed = collapsed;
contentPanel.setVisible(!collapsed);
toggleButton.setText(collapsed ? "\u25B6" : "\u25BC"); // ▶ / ▼
revalidate();
repaint();
}
/**
* Check if the panel is collapsed or not.
*
* @return Is the panel collapsed or not?
*/
public boolean isCollapsed() {
return collapsed;
}
/**
* Override addImpl so that user-added components go into the content area
* instead of directly into the outer BorderLayout.
*/
@Override
protected void addImpl(Component comp, Object constraints, int index) {
if (internalAdd) {
super.addImpl(comp, constraints, index);
} else {
contentPanel.add(comp, constraints, index);
}
}
/**
* Convenience factory for a titled, initially-collapsed panel.
*
* @param title The title for the panel
* @param layout The layout manager for the content
* @return The panel created
*/
public static CollapsiblePanel collapsed(String title, LayoutManager layout) {
CollapsiblePanel p = new CollapsiblePanel(title, layout);
p.setCollapsed(true);
return p;
}
}
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