JSplitPane + MiGLayout: how to enable autoresizing

I'm doing something wrong here: I want to have two JButtons in a JSplitPane in a JPanel in a a JFrame, where the buttons fill the JSplitPane.

Here's what I get when I resize the JFrame:

The buttons stay their normal size, and the JSplitPane doesn't allow adjusting.something

How do I fix this?

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JSplitPane;
import net.miginfocom.swing.MigLayout;

public class SplitPaneQuestion {
    public static void main(String[] args) {
        JFrame frame = new JFrame("SplitPaneQuestion");
        JPanel panel = new JPanel();
        frame.setContentPane(panel);
        panel.setLayout(new MigLayout("","[]","[grow]"));
        JSplitPane splitpane = new JSplitPan开发者_C百科e(JSplitPane.VERTICAL_SPLIT);
        panel.add(splitpane, "");

        splitpane.setTopComponent(new JButton("top"));
        splitpane.setBottomComponent(new JButton("bottom"));

        frame.pack();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }
}

Add the "push" and "grow" contraints to your split pane, like this:

panel.add(splitpane, "push, grow");