在JFrame中实现CardLayout并根据特定的按钮按下来切换卡
我已经在下面发布了我的代码。我有创建可导航GUI的简单任务。我花了过去的几个小时研究如何实现此目标，这是我编写的代码。
本来我想在没有任何布局或任何内容的情况下执行导航。用户单击欢迎面板上的“登录”按钮后，我需要显示主页面板。
它可以很好地显示欢迎卡，但是当我进入validateLogin方法（按下登录按钮时将被激活，并且成功登录后，它应显示卡中的主面板），即使我仍然停留在欢迎面板上已经验证我的程序已到达循环以通过system.out.Println（）更换卡
请帮忙。我花了整个星期六试图通过试验和研究解决这一问题，但没有成功。这对我来说是不得已的办法，因此，如果有人可以向我展示我的缺点，那么我会很乐意继续前进并进行修复。然后将该修复程序应用于我的程序所需的许多其他卡。
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");
}
}
}
回答：
您创建了一个使用CardLayout和卡片的JPanel，但是没有添加任何内容，因此它当然不会显示自身，也不会显示卡片。解决方案：将此JPanel添加到您的GUI。
所以代替：
main.setContentPane(welcomePanel());做：
main.setContentPane(cards);问题编号2：
将字符串用作键的类型时，请使用字符串常量。请注意，您因此将一个JPanel添加到卡JPanel中：
cards.add(home, "Home");但是，然后尝试像这样显示它：
cl.show(cards, "home");但是“家”与“家”不同。
而是声明一个常量HOME：
public static final String HOME = "home";并使用相同的常量添加并显示JPanel。
举一个简单的例子：
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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