java仿win7计算器布局

代码：

package calculator;
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class cal extends JFrame{
    private JTextField tf =new JTextField("0");

    public void addButton(String name,GridBagLayout g ,GridBagConstraints c){
        JButton btn = new JButton(name);
        g.setConstraints(btn, c);
        add(btn);
    }

    public void lauch(){
        //文本是不可以编辑的
        tf.setEditable(false);
        GridBagLayout gb = new GridBagLayout();
        setLayout(gb);
        GridBagConstraints c  = new GridBagConstraints();
        //文本是放在最上面的，占用那一行所有的空间
        c.weightx=0.3;
        c.weighty=0.3;
        c.gridy  = 0 ;
    //    c.anchor = GridBagConstraints.EAST;
        c.gridwidth = 4 ;
        c.fill = GridBagConstraints.BOTH;
        add(tf,c);

        //需要另起一行添加按钮
        c.gridy =1;

        c.gridwidth =1 ;
        addButton("MC", gb, c);
        addButton("M+", gb, c);
        addButton("M-", gb, c);
        addButton("MR", gb, c);
        c.gridy = 2;

        addButton("c", gb, c);
        addButton("+", gb, c);
        addButton("/", gb, c);
        addButton("*", gb, c);
        c.gridy = 3;

        addButton("7", gb, c);
        addButton("8", gb, c);
        addButton("9", gb, c);
        addButton("-", gb, c);
        c.gridy = 4;

        addButton("4", gb, c);
        addButton("5", gb, c);
        addButton("6", gb, c);
        addButton("+", gb, c);

        c.gridy = 5 ;
        addButton("1", gb, c);
        addButton("2", gb, c);
        addButton("3", gb, c);
        c.gridx = GridBagConstraints.RELATIVE;
        c.gridheight= GridBagConstraints.REMAINDER ;
        c.fill = GridBagConstraints.BOTH;
        //c.anchor  = GridBagConstraints.SOUTH;
        addButton("=", gb, c);
        c.gridy = 6 ;
        c.gridx= 0 ;
        c.gridheight = 1 ;
        c.gridwidth  =2 ;
        addButton("0",gb,c);
        c.gridx  = GridBagConstraints.RELATIVE;
        c.gridwidth  =1 ;
        addButton(".",gb,c);
    setBounds(100,100,300,500);
        //this.pack();
        setVisible(true);
    }

    public static void main(String[] args) {
            cal c = new cal();
            c.lauch();

    }

}