How to update the scrollbar?

[Martino]

Hi,

I have a little problem with programming a vertical scroll bar for scrolling a Graphics panel.

At specific moments, the vertical scroll bar is being updated. This is, because a new item is drawn to the panel or an item is removed. As a consequence the height of the panel changes, and so, the vertical scroll bar has to be changed too.

But now I have the following problem. When you, for example, make the frame bigger, the scroll bar should update, but it did not succeed.

How can I update the scroll bar, when the size of the window/panel changes? It is an event. But, what event is that? Is that an event of WindowListener or WindowStateListener? Please help! Thank you in advance!

[DarrylBurke]

Neither. ComponentListener.

But why are you reinventing JScrollPane?

db

[Martino]

Hi,

Thanks for the answer.

What do you mean with 'reinventing the wheel'? Is there an easier to build to scroll bar for scrolling graphics?

[camickr]

Is there an easier to build to scroll bar for scrolling graphics?

All you need to manage is the "preferred size" of you panel. Override the getPreferredSize() method to return the proper based based on the items your draw. Whenever you add/remove an item you invoke;

revalidate();
repaint();

on the panel and the layout manager code will look after the scrollbars of the scrollpane. Resizing of the frame will also be handled automatically as well.