Attach jscrollbar to another component

Question

In my application, I have two swing components on top of each other, that look something like this picture. The problem is that the orange component needs a vertical scrollbar, but I want the right edges of the components to stay exactly aligned (and the width can vary as the user makes the app wider or narrower). If I use something like a grid layout, the scrollbar takes up space and then the scrollbar lines up with the right edge of the red component.

I'm thinking I might need to use a scrollbar component and add that separately and use it to control the orange component. Is there a way to attach a scrollbar to another component like that? I would think it would be difficult without using a scrollpane. I'm also open to any suggestions on how else to approach this.

Answer 1

It shouldn't be too hard to implement the approach you suggested. Wrap the orange component in a JScrollPane, but configure the scroll pane to hide both scrollbars. Then, set the scroll model for the vertical scroll bar in the scroll pane to the scrolling model from the standalone scrollbar. Even though the scroll pane scroll bar is hidden, it will still scroll if the models are linked. See my answer in this question for some code - it's a different application but similar principle.

Alternatively, you could use a JScrollPane with a visible vertical scrollbar, and add a spacing component next to the red component to keep it aligned. I'm thinking you could use a GridBagLayout with two columns. The first row holds the red component and the spacer, and the second row holds the scroll pane with the orange component, which spans both columns. Then, you just have to get the width of the scroll bar component from the JScrollPane and set the preferred width of the spacer to the same value. A drawback with this strategy would be that it could be difficult to keep the spacer size updated if the scrollbar width changes (due to a UI change, for example).