与JFrame组件交互

Question

我正在尝试使用Swing构建一个非常简单的连接4游戏 主游戏按预期工作，但当我将其用作更大GUI中的组件时，我无法再与其进行交互。

这是主要的GUI代码：

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.GridLayout;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;

public class MainLayout extends JFrame {

    public MainLayout(){

        // TOP PANEL, series of button using FlowLayout
        JPanel topPanel = new JPanel(new FlowLayout(FlowLayout.CENTER, 30, 10));
        topPanel.setBackground(Color.BLUE);

        JButton newGameBtn = new JButton("New Game");
        topPanel.add(newGameBtn);

        this.setDefaultCloseOperation(EXIT_ON_CLOSE);
        this.setLayout(new BorderLayout(5,5));
        this.getContentPane().setBackground(Color.cyan);
        this.setTitle("Connect 4");

        JPanel grid = new JPanel(new GridLayout(6,7,3,3));
        grid.setBackground(Color.blue);

        board comp = new board(new Dimension(7,6), new Dimension(60, 60));
        comp.setFocusable(true);
        comp.setEnabled(true);
        this.getContentPane().add(topPanel, BorderLayout.NORTH);
        this.getContentPane().add(comp, BorderLayout.CENTER);
        this.setSize(420,430);
    }

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        MainLayout mainWindow = new MainLayout();
        mainWindow.setVisible(true);
    }
}

电路板组件使用键盘输入来移动方块。