Question

I have been trying to use JScrollPane with my applet, but it doesn’t work. I have a JPanel to which I add 20 buttons, and I want to be able to scroll up and down this JPanel. Instead, the scrollbars do not appear. When I use setPreferredSize they still did not appear even though only about 3 of the buttons are being displayed and the rest are cut off. If I do not use setPreferredSize, there might as well not be any scrollbars because I have to make the window big enough to see all of the buttons. If I try to make the scrollbars always visible, they appear but do nothing. I tried the exact same code with JFrame instead of Applet, and it works fine, but I need it to be an applet. Is JScrollPane incompatible with applets? (Note: I tried to use an outer JPanel and add the scrollable panel to it, but it changed nothing). Changing the layouts also doesn’t fix the problem. I have attached a simplified version of my code, but it displays the same errors.

Here is the code I have:

JPanel scrollPanel = new JPanel();
scrollPanel.setLayout(new BoxLayout(scrollPanel, BoxLayout.PAGE_AXIS));
JScrollPane scroll = new JScrollPane(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS,
                                    JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS);
for (int i = 0; i < 20; i++) scrollPanel.add(new JButton("Button " + i));
add(scrollPanel);
validate();

Answer 1

1. You never all the panel to the scroll pane
2. You never add the scroll pane to the applet

The basic code should be:

JScrollPane scrollPane = new JScrollPane(...);
scrollPane.setViewportView( scrollPanel );
add( scrollPane );