在 JFrame 中实现 CardLayout 并根据特定按钮按下切换卡片 [英] Implementing CardLayout within a JFrame and switching cards based on specific button presses

问题描述

我在下面发布了我的代码.我有创建可导航 GUI 的简单任务.在过去的几个小时里，我一直在研究如何做到这一点，这就是我整理的代码.

I've posted my code below. I have the simple task of creating a navigable GUI. I've spent the past few hours doing research on how to accomplish this, and this is the code that I've put together.

最初我想在没有任何布局或任何东西的情况下执行导航.我需要在用户单击欢迎面板上的登录"按钮后显示主页面板.

Originally I wanted to perform the navigation without any layouts or anything. I need the home panel to display after the user clicks on the "login" button on the welcome panel.

它很好地显示了欢迎卡，但是当我使用 validateLogin 方法(按下登录按钮时激活，成功登录后它应该在卡中显示主面板)它只是停留在欢迎面板上即使我已经验证我的程序通过 system.out.Println() 到达循环以更换卡片

It displays the welcome card just fine, but when I get to the validateLogin method(which is activated when the login button is press, and upon successful login it should show the home panel within cards) it simply stays on the welcome panel even though I have validated that my program reaches the loop to change cards via the system.out.Println()

请帮忙.我整个周六都在尝试通过试验和研究来解决这个问题，但没有成功.这对我来说是最后的手段，所以如果有人能向我展示我的缺陷，那么我会很高兴地去修复它.然后将该修复程序应用于我的程序所需的许多其他卡.

Please help. I spent my entire Saturday trying to solve this one problem through trials and research, but with no success. This is a last resort for me so if anyone can show me my flaws then I'll happily be on my way and fix it. Then apply that fix to the many other cards that are required for my program.

    enter code here
    public class mainGUI implements ActionListener{
JFrame main;
JPanel cards = new JPanel(new CardLayout());
CardLayout cl = (CardLayout)(cards.getLayout());

//Items for the welcome panel
JPanel welcome = welcomePanel();
JButton login;
JButton register;
JTextField username;
JTextField password;

//home panel
JPanel home = homePanel();


//WelcomePanel welcome = new WelcomePanel();

ArrayList<Student> students = new ArrayList<Student>();
Student workingStudent;


/**
 * calls load() at start and save() on exit
 * 
 */
public mainGUI(){
    load();

    main = new JFrame();
    main.setSize(900, 600);
    main.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    main.setTitle("MyCourses 2k16");
    main.setContentPane(welcomePanel());

    //fill out the cards
    cards.add(welcome, "Welcome");
    cards.add(home, "Home");
            //display welcome card
    cl.show(cards, "welcome");

    main.setVisible(true);

    saveState();
}

private JPanel welcomePanel() {
    JPanel welcome = new JPanel();
    welcome.setLayout(null);
    welcome.setBackground(Color.DARK_GRAY);

    JLabel hi = new JLabel("Welcome to MyCourses 2K16");
    hi.setSize(800, 100);
    hi.setLocation(50,50);
    hi.setFont(new Font("Serif", Font.BOLD, 48));
    hi.setForeground(Color.WHITE);

    JLabel select = new JLabel("Fill in the information, then click login or register to proceed, no special characters allowed");
    select.setSize(700,100);
    select.setLocation(75,100);
    select.setFont(new Font("Serif", Font.PLAIN, 18));
    select.setForeground(Color.WHITE);

    login = new JButton( "login");
    login.setSize(100, 50);
    login.setLocation(50, 200);
    login.addActionListener(this);

    register = new JButton( "register");
    register.setSize(100,50);
    register.setLocation(200, 200);
    register.addActionListener(this);

    JLabel un = new JLabel("username");
    un.setSize(100, 30);
    un.setLocation(50, 270);
    un.setForeground(Color.WHITE);

    username = new JTextField();
    username.setSize(200, 30);
    username.setLocation(50,300);

    JLabel pw = new JLabel("password");
    pw.setSize(100, 30);
    pw.setLocation(50, 350);
    pw.setForeground(Color.WHITE);

    password = new JTextField();
    password.setSize(200, 30);
    password.setLocation(50,380);

    welcome.add(hi);
    welcome.add(select);
    welcome.add(login);
    welcome.add(register);
    welcome.add(un);
    welcome.add(username);
    welcome.add(pw);
    welcome.add(password);

    return welcome;
}

private JPanel homePanel() {
    JPanel home = new JPanel();
    home.setLayout(null);
    home.setBackground(Color.DARK_GRAY);

    JLabel hi = new JLabel("HOME");
    hi.setSize(800, 100);
    hi.setLocation(50,50);
    hi.setFont(new Font("Serif", Font.BOLD, 48));
    hi.setForeground(Color.WHITE);

    return home;

}

public void load(){

}

private void saveState(){
    Iterator<Student> it = students.iterator();
    while(it.hasNext()){
        it.next().saveStudent();
    }
}



public static void main(String[] args) {

    new mainGUI();

}


@Override
public void actionPerformed(ActionEvent e) {
    if (e.getSource()==login){
        System.out.println("Logging in...");
        validateLogin(students);
    }
    else if (e.getSource()==register){

    }
}

private void validateLogin(ArrayList<Student> students){
    boolean valid = false;

    for(int i = 0; i < students.size(); i++){

        if(username.getText().equals(students.get(i).getUsername())
                && password.getText().equals(students.get(i).getPassword()))
        {   
            valid = true;
            workingStudent=(students.get(i));
            System.out.println("Successful Login!");
            cl.show(cards, "home");
        }
    }
    if(valid == false){
        System.out.println("Invalid Login, try again");
    }

}

}

推荐答案

您创建了一个使用 CardLayout 的 JPanel，卡片，但是您将它添加到任何内容中，所以它当然不会显示自己，也不会显示它的卡片.解决方案:将此 JPanel 添加到您的 GUI.

You create a JPanel that uses CardLayout, cards, but you add it to nothing, so it will of course not display itself, nor its cards. Solution: add this JPanel to your GUI.

所以而不是:

main.setContentPane(welcomePanel());

做:

main.setContentPane(cards);

<小时>

问题编号 2:

---

Issue number 2:

使用字符串作为键类型时使用字符串常量.请注意，您将一个 JPanel 添加到卡片 JPanel 中:

Use String constants when using Strings as a type of key. Note that you add one JPanel to the cards JPanel thusly:

cards.add(home, "Home");

然后尝试像这样显示它:

But then try to display it like so:

cl.show(cards, "home");

但家不等于家.

改为声明一个常量 HOME:

Instead declare a constant, HOME:

public static final String HOME = "home";

并使用相同的常量来添加 JPanel 并显示它.

and use the same constant to add the JPanel and to display it.

举个简单的例子:

import java.awt.CardLayout;
import java.awt.event.ActionEvent;

import javax.swing.*;

public class MainGui2 extends JPanel {
    private CardLayout cardLayout = new CardLayout();
    private WelcomePanel welcomePanel = new WelcomePanel(this);
    private HomePanel homePanel = new HomePanel();

    public MainGui2() {
        setLayout(cardLayout);
        add(welcomePanel, WelcomePanel.NAME);
        add(homePanel, HomePanel.NAME);
    }

    public void showCard(String name) {
        cardLayout.show(this, name);
    }

    private static void createAndShowGui() {
        MainGui2 mainPanel = new MainGui2();

        JFrame frame = new JFrame("MainGui2");
        frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
        frame.getContentPane().add(mainPanel);
        frame.pack();
        frame.setLocationByPlatform(true);
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                createAndShowGui();
            }
        });
    }

}

class WelcomePanel extends JPanel {
    public static final String NAME = "welcome panel";
    private MainGui2 mainGui2;

    public WelcomePanel(final MainGui2 mainGui2) {
        this.mainGui2 = mainGui2;
        add(new JLabel(NAME));
        add(new JButton(new AbstractAction("Logon") {

            @Override
            public void actionPerformed(ActionEvent e) {
                mainGui2.showCard(HomePanel.NAME);
            }
        }));
    }
}

class HomePanel extends JPanel {
    public static final String NAME = "home panel";

    public HomePanel() {
        add(new JLabel(NAME));
    }
}

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