卡片布局 - java GUI

Question

Java 中的 CardLayout() 是如何工作的？我使用了互联网，但似乎无法让 CardLayout 工作。这是我到目前为止的代码，但它不起作用：

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
public class GameManager
{
    JFrame frame;
    JPanel cards,title;
    public GameManager()
    {
        cards = new JPanel(new CardLayout());
        title = new JPanel();
        cards.add(title,"title");
        CardLayout cl = (CardLayout)(cards.getLayout());
        cl.show(cards, "title");
    }
    public static void main(String [] args)
    {
        GameManager gm = new GameManager();
        gm.run();
    }
    public void run()
    {
        frame = new JFrame("Greek Olympics");
        frame.setSize(1000,1000);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().add(cards);
        frame.setVisible(true);
        CardLayout cl = (CardLayout)(cards.getLayout());
        cl.show(cards, "title");
    }
    public class title extends JPanel
    {
        public void paintComponent(Graphics g)
        {
            super.paintComponent(g);
            g.fillRect(100,100,100,100);
        }
    }
}

我应该怎么做才能让面板标题显示我绘制的矩形，因为它没有显示我到目前为止的代码。

Answer 1

初始化局部变量 title 时，您正在创建 JPanel 的实例，而不是您定义的 title 类。

为了清楚起见并遵守 Java 命名约定，您应该将类​​名大写 (Title)。然后您需要将title 变量的类型更改为Title。

这是更新后的代码，我突出显示的地方发生了变化。

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
public class GameManager {
    JFrame frame;
    JPanel cards; // <-----
    Title title; // <-----

    public GameManager(){
        cards = new JPanel(new CardLayout());
        title = new Title(); // <-----
        cards.add(title,"title");
        CardLayout cl = (CardLayout)(cards.getLayout());
        cl.show(cards, "title");
    }

    public static void main(String [] args){
        GameManager gm = new GameManager();
        gm.run();
    }

    public void run(){
        frame = new JFrame("Greek Olympics");
        frame.setSize(1000,1000);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().add(cards);
        frame.setVisible(true);
        CardLayout cl = (CardLayout)(cards.getLayout());
        cl.show(cards, "title");
    }

    public class Title extends JPanel { // <-----
        public void paintComponent(Graphics g){
            super.paintComponent(g);
            g.fillRect(100,100,100,100);
        }
    }
}