CODEWITHSUNDEEP
javaswingjscrollpane
Quillion
Quillion

Reputation: 6476

Change JScrollPane scroll speed based on height

I would like to change the scroll speed of a JScrollPane based on its height.

This is how I am currently creating my JScrollPane:

JScrollPane scrollPane = new JScrollPane(table);
scrollPane.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
scrollPane.setHorizontalScrollBarPolicy(ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);
scrollPane.getVerticalScrollBar().setUnitIncrement(scrollSpeed);

The problem is that setUnitIncrement needs to change the scroll speed dynamically. I am not aware of how I would go about doing that.

Ideally, I would like to scroll by half the height of the scroll pane whenever the user uses mouse wheel button, or presses one of the scroll up or down buttons on the scroll bar.

Upvotes: 0

Views: 180

Answers (1)

Chris Sprague
Chris Sprague

Reputation: 740

In my experience, the speed at which you scroll through a scroll pane does not (and should not) change dynamically based on the pane's size (e.g. how many elements are in a view port's list or something.)

That said, if you need to, try this:

int getNewScrollSpeed( int scrollPaneHeight ){

    // you'll have to play around with the multiplier value to make it work for you
    // here I just chose 0.5 as an example

    return (int) ( scrollPaneHeight * 0.5 );

}

Then call this routine like this, whenever the scrollPane's or window's (etc.) height changes.

    /* scrollPane height changes occur here */

    scrollPane.getVerticalScrollBar().setUnitIncrement( 
        getNewScrollSpeed ( scrollPane.getHeight() );

Upvotes: 1

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