Code
/*
- RoundedTitledBorder
- [TitledBorder(Border, String)](https://docs.oracle.com/javase/8/docs/api/javax/swing/border/TitledBorder.html#TitledBorder-javax.swing.border.Border-java.lang.String-) creates a `TitledBorder` that uses `RoundedBorder` for rounded corners.
- Additionally, it overrides `TitledBorder#paintBorder(...)` to draw a rounded rectangle with rounded bottom-right corners as the background for the title text.
*/
class RoundedTitledBorder extends TitledBorder {
private final JLabel label = new JLabel(" ");
private final int arc;
protected RoundedTitledBorder(String title, int arc) {
super(new RoundedBorder(arc), title);
this.arc = arc;
}
@Override public void paintBorder(
Component c, Graphics g, int x, int y, int width, int height) {
Graphics2D g2 = (Graphics2D) g.create();
g2.setRenderingHint(
RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
Border b = getBorder();
if (b instanceof RoundedBorder) {
Dimension d = getLabel(c).getPreferredSize();
Insets i = b.getBorderInsets(c);
int a2 = arc * 2;
int w = d.width + i.left + i.right + a2;
int h = d.height + i.top + i.bottom;
g2.setClip(((RoundedBorder) b).getBorderShape(
x + i.left, y + i.top, w, h));
g2.setPaint(Color.GRAY);
Shape titleBg = new RoundRectangle2D.Float(
x - a2, y - a2, w + a2, h + a2, arc, arc);
g2.fill(titleBg);
g2.dispose();
}
g2.dispose();
super.paintBorder(c, g, x, y, width, height);
}
private JLabel getLabel(Component c) {
this.label.setText(getTitle());
this.label.setFont(getFont(c));
this.label.setComponentOrientation(c.getComponentOrientation());
this.label.setEnabled(c.isEnabled());
return this.label;
}
}
class RoundedBorder extends EmptyBorder {
private static final Paint ALPHA_ZERO = new Color(0x0, true);
private final int arc;
protected RoundedBorder(int arc) {
super(2, 2, 2, 2);
this.arc = arc;
}
@Override public void paintBorder(
Component c, Graphics g, int x, int y, int width, int height) {
Graphics2D g2 = (Graphics2D) g.create();
g2.setRenderingHint(
RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
Shape border = getBorderShape(x, y, width, height);
g2.setPaint(ALPHA_ZERO);
Area clear = new Area(new Rectangle2D.Double(x, y, width, height));
clear.subtract(new Area(border));
g2.fill(clear);
g2.setPaint(Color.GRAY);
g2.setStroke(new BasicStroke(1.5f));
g2.draw(border);
g2.dispose();
}
protected Shape getBorderShape(int x, int y, int w, int h) {
return new RoundRectangle2D.Double(x, y, w - 1, h - 1, arc, arc);
}
}
/*
- TitleLayerUI
- This implementation does not use `TitledBorder` itself, but instead configures a `RoundedBorder` for rounded corners and sets the title to be drawn using a `JLayer`.
- It overrides `LayerUI#paint(...)` to draw the title text within the component.
- Within `LayerUI#paint(...)`, it configures the title text to be shown or hidden based on whether the component has focus, and overrides `LayerUI#processFocusEvent` to redraw the entire component and update the border and title text whenever a focus change event occurs.
*/
class TitleLayerUI extends LayerUI<JScrollPane> {
private final JLabel label;
protected TitleLayerUI(String title, int arc) {
super();
label = new RoundedLabel(title, arc);
label.setBorder(BorderFactory.createEmptyBorder(2, 10, 2, 10));
// label.setOpaque(false);
label.setForeground(Color.WHITE);
label.setBackground(Color.GRAY);
}
@Override public void paint(Graphics g, JComponent c) {
super.paint(g, c);
if (c instanceof JLayer) {
JScrollPane sp = (JScrollPane) ((JLayer<?>) c).getView();
Rectangle r = SwingUtilities.calculateInnerArea(sp, sp.getBounds());
if (r != null && !sp.getViewport().getView().hasFocus()) {
Dimension d = label.getPreferredSize();
SwingUtilities.paintComponent(
g, label, sp, r.x - 1, r.y - 1, d.width, d.height);
}
}
}
@Override public void updateUI(JLayer<? extends JScrollPane> l) {
super.updateUI(l);
SwingUtilities.updateComponentTreeUI(label);
}
@Override public void installUI(JComponent c) {
super.installUI(c);
if (c instanceof JLayer) {
((JLayer<?>) c).setLayerEventMask(AWTEvent.FOCUS_EVENT_MASK);
}
}
@Override public void uninstallUI(JComponent c) {
if (c instanceof JLayer) {
((JLayer<?>) c).setLayerEventMask(0);
}
super.uninstallUI(c);
}
@Override protected void processFocusEvent(
FocusEvent e, JLayer<? extends JScrollPane> l) {
super.processFocusEvent(e, l);
l.getView().repaint();
}
private static class RoundedLabel extends JLabel {
private final int arc;
public RoundedLabel(String title, int arc) {
super(title);
this.arc = arc;
}
@Override protected void paintComponent(Graphics g) {
if (!isOpaque()) {
Dimension d = getPreferredSize();
int w = d.width - 1;
int h = d.height - 1;
int h2 = h / 2;
Graphics2D g2 = (Graphics2D) g.create();
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
g2.setPaint(getBackground());
g2.fillRect(0, 0, w, h2);
g2.fillRoundRect(-arc, 0, w + arc, h, arc, arc);
g2.dispose();
}
super.paintComponent(g);
}
}
}
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