另一个可滚动的JPanel内的完整JPanel高度

Question

我使用swingx和miglayout扩展，但我遇到了问题。我有以下代码：

public class App {

public static void main(String[] args) {
    SwingUtilities.invokeLater(new Runnable() {

        @Override
        public void run() {
            JFrame frame = new JFrame();

            frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            frame.setLayout(new MigLayout());

            JXPanel keysPanel = new JXPanel();
            JXPanel keysPanelContainer = new JXPanel();
            JScrollPane scrollPane = new JScrollPane(keysPanelContainer,

                    ScrollPaneConstants.VERTICAL_SCROLLBAR_AS_NEEDED,
                    ScrollPaneConstants.HORIZONTAL_SCROLLBAR_AS_NEEDED);

            JButton nextButton = new JButton("Next");

            keysPanel.setLayout(new MigLayout());
            keysPanelContainer.setLayout(new MigLayout());
            scrollPane.setBorder(BorderFactory.createEmptyBorder());
            keysPanelContainer.setScrollableHeightHint(ScrollableSizeHint.PREFERRED_STRETCH);

            keysPanelContainer.add(keysPanel, "w 100%, h 100%");
            frame.add(scrollPane, "w 100%, h 100%");
            frame.add(nextButton, "newLine, right");

            frame.setSize(600, 320);
            frame.setLocationRelativeTo(null);

            frame.setVisible(true);
        }
    });

 }
}

当我运行此代码时，如果我的keysPanel增加到无穷大，则为高度。我的代码有什么问题？我需要keysPanel高度100％。