将JScrollpane添加到包含多个JPanel的JPanel中

Question

I have one JFrame (black) that contains one main JPanel (grey), this JPanel contains three other JPanels : North and South (red) and the Center one (blue). The blue JPanel in the center will have lots of JPanels (green) added dynamically to it during the course of the program. When the Center JPanel is full I would like a JScrollbar to appear automatically to scroll down the Center Panel and see all the child (green) panels it contains. Can somebody help me? The problem is that the scrollbar isn't appearing at all, if i add 15 green JPanels to my blue JPanel container, i only see 10 and i can't scroll down.

This is the type of code i have tried so far...

    JPanel panelNorth = new JPanel(new GridBagLayout());
    panelNorth.setPreferredSize(new Dimension(1000,100);
    //add some labels and buttons

    JPanel panelCenter = new JPanel();
    panelCenter.setLayout(new BoxLayout(panelCenter, BoxLayout.Y_AXIS));
    panelCenter.setPreferredSize(new Dimension(1000,500)
    JPanel panel1 = new JPanel(new GridLayout(1, 10));
    panel1.setPreferredSize(new Dimension(1000,50));
    panelCenter.add(panel1);
    //...etc dynamically


    JPanel panelSouth = new JPanel(new GridBagLayout());
    panelSouth.setPreferredSize(new Dimension(1000,100);
    //add some labels and buttons

    JScrollPane scrollPaneCenter = new JScrollPane(panelCenter,JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED,JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
    //panelCenter must be scrollable when too many panels are added to panelCenter

    //add everything to the main panel container
    JPanel panelContainer = new JPanel(new BorderLayout(3,3));
    panelContainer.setBorder(new EmptyBorder(5,5,5,5));
    panelContainer.add(panelNorth,BorderLayout.NORTH);
    panelContainer.add(scrollPaneCenter,BorderLayout.CENTER);
    panelContainer.add(panelSouth,BorderLayout.SOUTH);

    //add everything to frame   
    JFrame frame = new JFrame();
    frame.add(panelContainer);

Thank you.

EDIT: I changed

 JScrollPane scrollPaneCenter = new    JScrollPane(panelCenter,JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED,JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);

to this :

 JScrollPane scrollPane = new JScrollPane(panelCentre,JScrollPane.VERTICAL_SCROLLBAR_ALWAYS,JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS);

And this is what i get:

I can see it now, it's in the right place, i just can't scroll down to see my other components.

Answer 1

Fixed it by switching

panelCenter.setPreferredSize(new Dimension(1000,500);

with

scrollPane.setPreferredSize(new Dimension(1000,500));