AutoScroll when Shape is outside a JPanel

Question

I have a JPanel where I draw shapes. this panel is added to a scrollPane. but the scrolling doesn't work when a shape is out of the scene. is there an easy way to autoscroll or I have to do it programmatically.

Thank you

Answer 1

I'm assuming you're using the JPanel as a canvas for custom drawing(i.e. you're not adding any JComponents to it). If that's case, the JScrollPane has no way of knowing how large the JPanel is and will just size it to exactly fill the scrollPane's viewport(which means you'll never actually get scroll bars).

To fix this issue you should override getPreferredSize on your JPanel.

@Override     
public Dimension getPreferredSize() {
    int height = calculateHeight(); 
    int width = calculateWidth(); 
    return new Dimension(width, height);
}

Edit:

Also, since you're doing custom drawing make sure to call revalidate whenever the shapes you want to draw change. This tells swing that it needs to re-think the layout/size of the JPanel.