Harsha Harsha - 3 months ago 18
Java Question

How to scroll to a specific location in a JScrollPane

I have a JScrollPane which contains a JPanel which has large height, This large JPanel contain more Jpanels in it as in the image. Some of those panels contains a JLabel which I used to show titles. At the top, there are JLabels which have numbers matching the title numbers in the title labels. What I need to do is when I click a label from the top label list the JScrollBar should scroll to the position where that label is placed.

I don't know whether this is possible or not, but if anyone know how to scroll to a specific position in a JScrollPane please assist me.

enter image description here

Answer

Assuming you want the whole panel that contains the label as title to be visible:

Container parent = titleLabel.getParent();
parent.scrollRectToVisible(parent.getBounds());

There's no need to access the containing viewport/scrollPane except (there's always an except, isn't it :-)

  • the component the scrollRectToVisible is invoked on has a custom implementation (as f.i. text components
  • if the default location reached by that method isn't up to your liking

Edit

a code snippet for @MadProgrammer :-) - but too lazy to remove every trace of SwingX, so here we go:

final JLabel last = new JLabel("I'm the last");

int maxRow = 20;
int maxColumn = 10;

JComponent content = new JPanel(new GridLayout(maxRow, maxColumn));
for (int row = 0; row < maxRow; row++) {
    for (int column = 0; column < maxColumn; column++) {
        JComponent parent = new JPanel();
        JLabel label = new JLabel("i'm in " + row + "/" + column);
        if (row == (maxRow - 1) && column == (maxColumn - 1)) {
            label = last;
            last.setBorder(BorderFactory.createLineBorder(Color.RED));
        }
        parent.add(label);
        content.add(parent);
    }
}
JXFrame frame = wrapWithScrollingInFrame(content, "scroll");
Action action = new AbstractAction("scrollLastVisible") {

    @Override
    public void actionPerformed(ActionEvent e) {
        last.scrollRectToVisible(last.getBounds());
    }
};
addAction(frame, action);
show(frame, frame.getPreferredSize().width / 2, frame.getPreferredSize().height / 2);
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