GridBagLayout小问题

import java.awt.*;

import javax.swing.JPanel;



public class GridBagEx22 extends JPanel {



	protected void makebutton(String name,GridBagLayout gridbag,GridBagConstraints c) {

        Button button = new Button(name);

        gridbag.setConstraints(button, c);

        add(button);

    }



    public void init() {

        GridBagLayout gridbag = new GridBagLayout();

        GridBagConstraints c = new GridBagConstraints();

        setLayout(gridbag);



        c.fill = GridBagConstraints.BOTH;

        c.weightx = 1.0;

        c.gridwidth = GridBagConstraints.REMAINDER; //end row

        makebutton("Button1", gridbag, c);

        makebutton("Button2", gridbag, c);

        makebutton("Button3", gridbag, c);



        setSize(500, 300);

    }



    public static void main(String args[]) {

          Frame f = new Frame("GridBag Layout Example");

          GridBagEx22 ex1 = new GridBagEx22();



          ex1.init();



          f.add("Center", ex1);

          f.setSize(500,400);

          f.setVisible(true);

    }

}