Custom Java tool tip with Swing components as content does not show up

Question

I\'m trying to show multiple images in a component\'s tooltip, found createToolTip() and implemented a custom that adds the needed components like this:

Answer 1

There are essentially two things missing. First of all, JToolTip extends JComponent, and unlike JPanel, it doesn't have a default layout. To stretch the content across the tooltip, use a BorderLayout.

setLayout(new BorderLayout());

The second problem is the size. The ToolTipManager respects the preferred size of the tool tip. While the BorderLayout calculates the size, the ToolTipUI ignores it. So, there are two alternatives: Manually set the preferred size...

setPreferredSize(content.getPreferredSize());

Note that this does not make the layout obsolete; otherwise, you get an empty tool tip with the right size.

... or subclass ToolTipUI to respect the layout, which is what I went with. The resulting code is:

setComponent(StadtLabel.this);

JPanel images = new JPanel(null);
waren.setLayout(new BoxLayout(waren, BoxLayout.X_AXIS));
for(ImageIcon icon:myIcons) {
    JLabel lbl = new JLabel(icon);
}

JPanel content = new JPanel(new BorderLayout());
content.add(new JLabel(title), BorderLayout.NORTH);
content.add(new JLabel(description));
content.add(images, BorderLayout.SOUTH);

setLayout(new BorderLayout());
add(content);
setUI(new ToolTipUI() {
    @Override
    public Dimension getMinimumSize(JComponent c) {
        return c.getLayout().minimumLayoutSize(c);
    }

    @Override
    public Dimension getPreferredSize(JComponent c) {
        return c.getLayout().preferredLayoutSize(c);
    }

    @Override
    public Dimension getMaximumSize(JComponent c) {
        return getPreferredSize(c);
    }
});