如何使用基于它的阵列刷新GridLayout中放置的组件？

Question

我正在GridLayout中创建基于JTextFields的excel电子表格。我希望能够在单元格中键入内容，按Enter键，并根据输入字符串将单元格设置为适当的子类。

Cell I唯一正在工作的子类是DateCell。我可以成功地将子类设置在2d Cell数组中的正确位置;但是，这不会显示在GUI中，并且我当前的刷新方法不起作用。我希望它更新JFrame以在JTextFields中显示新文本。

任何关于为什么刷新方法不起作用的建议，刷新方法如何工作，或者在没有刷新方法的情况下执行程序的方法都将深表赞赏。谢谢！

这是GUI类：

package spreadsheet;

import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JFrame;
import javax.swing.JTextField;
import cell.*;

public class GUI extends JFrame {

    public  static final int ASCII_SHIFT = 64;

    private JTextField[][] grid;
    private Cell[][] sheet;

    public GUI(int height, char letter) {

        //sets the title to "TextExcel"
        super("TextExcel");

        //creates multidimensional Cell array
        sheet = new Cell[height][letter - ASCII_SHIFT + 1];

        //creates an array of text fields
        grid = new JTextField[sheet.length + 1][sheet[0].length];

        //creates a grid layout
        setLayout(new GridLayout(grid.length, grid[0].length));

        //create event handler
        Handler handler = new Handler();

        //makes the corner box blank
        grid[0][0] = new JTextField();
        grid[0][0].setEditable(false);

        //numbers the rows
        for (int i = 1; i < grid.length; i++) {
            grid[i][0] = new JTextField(Integer.toString(i));
            grid[i][0].setEditable(false);
        }

        //letters the columns
        for (int j = 1; j < grid[0].length; j++) {
            byte[] character = {(byte) (j + ASCII_SHIFT)};
            grid[0][j] = new JTextField(new String(character));
            grid[0][j].setEditable(false);
        }

        //initializes the cells
        for (int row = 1; row < grid.length; row++) {
            for (int col = 1; col < grid[0].length; col++) {
                if (sheet[row-1][col-1] == null) {
                    grid[row][col] = new JTextField();
                } else {
                grid[row][col] = new JTextField(sheet[row-1][col-1].toString());
                }
                grid[row][col].addActionListener(handler);
            }
        }

        //adds the boxes to the GUI
        for (int i = 0; i < grid.length; i++) {
            for (int j = 0; j < grid[0].length; j++) {
                grid[i][j].setHorizontalAlignment(JTextField.CENTER);
                add(grid[i][j]);
            }
        }           
    }

    public GUI() {
        this(10, 'G');
    }

    //will eventually return proper subclass
    public Cell parse(String s) {
        Cell output = new DateCell(s);
        return output;
    }

    public void refresh() {
        for (int row = 1; row < grid.length; row++) {
            for (int col = 1; col < grid[0].length; col++) {
                if (sheet[row - 1][col - 1] != null && !grid[row][col].getText().equals(sheet[row - 1][col - 1].toString())) {
                    grid[row][col] = new JTextField(sheet[row - 1][col - 1].toString());
                    System.out.println(sheet[row - 1][col - 1].toString());
                }
            }
        }
    }

    private class Handler implements ActionListener {

        public void actionPerformed(ActionEvent e) {
            for (int row = 1; row < grid.length; row++) {
                for (int col = 1; col < grid[0].length; col++) {
                    if (grid[row][col] == e.getSource()) {
                        sheet[row - 1][col - 1] = parse(e.getActionCommand());
                        refresh();
                    }
                }
            }
        }

    }

}

以下是客户端代码：

package client;

import javax.swing.JFrame;
import spreadsheet.GUI;

public class Program {
    public static void main(String[] args) {
        GUI gui = new GUI();
        gui.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        gui.setSize(1000, 618);
        gui.setVisible(true);
    }

}

Cell类就是这样：

package cell;

abstract public class Cell {

}

和DateCell类：

package cell;

public class DateCell extends Cell{

    private int month, day, year;
    public static final String[] MONTH = {"January", "February", "March", "April", "May",
            "June", "July", "August", "September", "October", "November", "December"};

    public DateCell(int month, int day, int year) {
        this.month = month;
        this.day = day;
        this.year = year;
    }

    public DateCell(String s) {
        int firstSlash = s.indexOf('/');
        int secondSlash = s.lastIndexOf('/');
        month = Integer.parseInt(s.substring(0, firstSlash));
        day = Integer.parseInt(s.substring(firstSlash + 1, secondSlash));
        if (s.substring(secondSlash + 1).length() < 4) {
            year = Integer.parseInt(s.substring(secondSlash + 1)) + 2000;
        } else {
            year = Integer.parseInt(s.substring(secondSlash + 1));
        }
    }

    public String toString() {
        return MONTH[month-1] + " " + day + ", " + year;
    }
}