Zooming in and zooming out within a panel
I have a Panel in which some 2D objects are moving about. I have overridden paintComponent() as necessary. Now I want to be able to zoom in and zoom out that area. When zooming in, scrollbars will appear by which one can view the entire field by scrolling. While zooming in and out, the 2D objects should increase or decrease in size accordingly. Which Swing component or rather combination of components will help to achieve this?
Answer
Easiest way is to modify your panel and introduce a double indicating your zoom level. This double would indicate your scale, where 1 is normal and higher is zoomed in. You can use that double together with Graphics2D in your paintComponent.
Such as:
Graphics2D g2 = (Graphics2D) g;
int w = // real width of canvas
int h = // real height of canvas
// Translate used to make sure scale is centered
g2.translate(w/2, h/2);
g2.scale(scale, scale);
g2.translate(-w/2, -h/2);
For the scrolling, put your panel in a JScrollPane and combine that with a getPreferredSize that also uses your zoom scale. JScrollPane uses the preferred size of the component you put in it. It will show scrollbars if the preferred size exceeds its own size.
If you change the preferred size of your panel so that the width and height it returns is scaled you should be fine. Basically you can just return something like:
return new Dimension(w * scale, h * scale)