我做了一个parentPanel，上面有一个CardLayout，在此我已经制作了4个JPanel容器。
在左侧我有4个按钮，当我按下"Forside"（按钮）我想切换到卡布局（Forside）上的面板，依此类推......
我尝试了不同的youtube教程，并试图在这里看到没有任何成功。我尝试的一切都以NullPointerException结束了
public class Main extends JFrame {
private JPanel contentPane;
int xx, xy;
/**
* Launch the application.
*/
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
Main frame = new Main();
frame.setUndecorated(true); // Hides the jframe top bar
frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
/**
* Create the frame.
*/
public Main() {
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setBounds(100, 100, 735, 506);
contentPane = new JPanel();
contentPane.setBackground(new Color(102, 102, 102));
contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
setContentPane(contentPane);
contentPane.setLayout(null);
JPanel panelLeft = new JPanel();
panelLeft.setBackground(new Color(51, 51, 51));
panelLeft.setForeground(Color.DARK_GRAY);
panelLeft.setBounds(0, 54, 150, 459);
contentPane.add(panelLeft);
panelLeft.setLayout(null);
JButton btnForside = new JButton("Forside");
btnForside.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
}
});
btnForside.setCursor(Cursor.getPredefinedCursor(Cursor.HAND_CURSOR));
btnForside.setForeground(Color.WHITE);
btnForside.setFont(new Font("Tahoma", Font.PLAIN, 17));
btnForside.setIcon(new ImageIcon(Main.class.getResource("/Images/icons8_Home_32px_1.png")));
btnForside.setContentAreaFilled(false);
btnForside.setBorderPainted(false);
btnForside.setBorder(null);
btnForside.setBounds(16, 60, 112, 30);
panelLeft.add(btnForside);
JButton btnDagbog = new JButton("Dagbog");
btnDagbog.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
}
});
btnDagbog.setCursor(Cursor.getPredefinedCursor(Cursor.HAND_CURSOR));
btnDagbog.setContentAreaFilled(false);
btnDagbog.setBorderPainted(false);
btnDagbog.setBorder(null);
btnDagbog.setFont(new Font("Tahoma", Font.PLAIN, 17));
btnDagbog.setForeground(Color.WHITE);
btnDagbog.setIcon(new ImageIcon(Main.class.getResource("/Images/icons8_Book_32px.png")));
btnDagbog.setBounds(16, 116, 112, 30);
panelLeft.add(btnDagbog);
JButton btnAftaler = new JButton("Aftaler");
btnAftaler.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
}
});
btnAftaler.setCursor(Cursor.getPredefinedCursor(Cursor.HAND_CURSOR));
btnAftaler.setContentAreaFilled(false);
btnAftaler.setBorderPainted(false);
btnAftaler.setBorder(null);
btnAftaler.setForeground(Color.WHITE);
btnAftaler.setFont(new Font("Tahoma", Font.PLAIN, 17));
btnAftaler.setIcon(new ImageIcon(Main.class.getResource("/Images/icons8_Planner_32px.png")));
btnAftaler.setBounds(16, 173, 112, 30);
panelLeft.add(btnAftaler);
JButton btnKontakt = new JButton("Kontakt");
btnKontakt.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
}
});
btnKontakt.setCursor(Cursor.getPredefinedCursor(Cursor.HAND_CURSOR));
btnKontakt.setContentAreaFilled(false);
btnKontakt.setBorder(null);
btnKontakt.setBorderPainted(false);
btnKontakt.setFont(new Font("Tahoma", Font.PLAIN, 17));
btnKontakt.setForeground(Color.WHITE);
btnKontakt.setIcon(new ImageIcon(Main.class.getResource("/Images/icons8_Phone_32px.png")));
btnKontakt.setBounds(16, 231, 112, 30);
panelLeft.add(btnKontakt);
JPanel panelTop = new JPanel();
panelTop.addMouseMotionListener(new MouseMotionAdapter() {
@Override
public void mouseDragged(MouseEvent arg0) {
int x = arg0.getXOnScreen(); // makes uggerhøj picture dragable
int y = arg0.getYOnScreen(); // makes uggerhøj picture dragable
Main.this.setLocation(x - xx, y - xy); // makes uggerhøj picture dragable
}
});
panelTop.addMouseListener(new MouseAdapter() {
@Override
public void mousePressed(MouseEvent e) {
xx = e.getX(); // makes uggerhøj picture dragable
xy = e.getY(); // makes uggerhøj picture dragable
}
});
panelTop.setBackground(new Color(51, 51, 51));
panelTop.setBounds(0, 0, 737, 60);
contentPane.add(panelTop);
panelTop.setLayout(null);
JButton btnX = new JButton("X");
btnX.setCursor(Cursor.getPredefinedCursor(Cursor.HAND_CURSOR));
btnX.setRolloverIcon(null);
btnX.setFont(new Font("Tahoma", Font.BOLD, 18));
btnX.setFocusTraversalKeysEnabled(false);
btnX.setFocusPainted(false);
btnX.setBorderPainted(false);
btnX.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
System.exit(0);
}
});
btnX.setContentAreaFilled(false);
btnX.setForeground(SystemColor.activeCaption);
btnX.setBorder(null);
btnX.setBounds(615, 13, 97, 25);
panelTop.add(btnX);
JPanel parentPanel = new JPanel();
parentPanel.setBackground(Color.GRAY);
parentPanel.setBounds(148, 54, 569, 405);
contentPane.add(parentPanel);
parentPanel.setLayout(new CardLayout(0, 0));
JPanel Forside = new JPanel();
parentPanel.add(Forside, "name_1472174211097300");
Forside.setFocusable(false);
JButton btnTest = new JButton("test");
Forside.add(btnTest);
JPanel Dagbog = new JPanel();
parentPanel.add(Dagbog, "name_1472176236196000");
JLabel lblTest = new JLabel("dagbog");
Dagbog.add(lblTest);
JPanel Aftaler = new JPanel();
parentPanel.add(Aftaler, "name_1472177885026100");
JPanel Kontakt = new JPanel();
parentPanel.add(Kontakt, "name_1472179607862700");
}
}
我只是想要它，所以正确的按钮会导致正确的卡片。
首先请下一次@AndrewThompson建议你制作代码的MCVE，并且@camickr在进入实际代码之前，在几步之内就测试和调试提出建议（这是专家编程101）。
CardLayout对象通过该方法在容器的内容之间切换
CardLayout.show(Container parent, String name);
在你的挥杆代码中进行导航时要记住DO-not在一个方法中制作你的Components字段而不是使它成为局部变量（至少在你的情况下是parentPanel和CardLayout）
所以为了让你的parentPanel在你的4个面板之间切换（抱歉我不熟悉你的语言），我做了一个相当重构的代码版本。
import java.awt.CardLayout;
import java.awt.Color;
import java.awt.Cursor;
import java.awt.EventQueue;
import java.awt.Font;
import java.awt.GridLayout;
import java.awt.SystemColor;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionAdapter;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.border.EmptyBorder;
import javax.swing.border.TitledBorder;
public class Main extends JFrame {
private JPanel contentPane;
int xx, xy;
/**
* Launch the application.
*/
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
Main frame = new Main();
frame.setUndecorated(true); // Hides the jframe top bar
frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
/**
* Create the frame.
*/
public Main() {
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setBounds(100, 100, 735, 506);
contentPane = new JPanel();
contentPane.setBackground(new Color(102, 102, 102));
contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
setContentPane(contentPane);
contentPane.setLayout(null);
JPanel Forside = new JPanel();
JPanel Dagbog = new JPanel();
JPanel Aftaler = new JPanel();
JPanel Kontakt = new JPanel();
JPanel panelLeft = new JPanel();
panelLeft.setBackground(new Color(51, 51, 51));
panelLeft.setForeground(Color.DARK_GRAY);
panelLeft.setBounds(0, 54, 150, 459);
contentPane.add(panelLeft);
panelLeft.setLayout(null);
JButton btnForside = new JButton("Forside");
btnForside.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
setCardLayoutView("name_1472174211097300");
}
});
btnForside.setCursor(Cursor.getPredefinedCursor(Cursor.HAND_CURSOR));
btnForside.setForeground(Color.WHITE);
btnForside.setFont(new Font("Tahoma", Font.PLAIN, 17));
btnForside.setIcon(new ImageIcon(Main.class.getResource("/Images/icons8_Home_32px_1.png")));
btnForside.setContentAreaFilled(false);
btnForside.setBorderPainted(false);
btnForside.setBorder(null);
btnForside.setBounds(16, 60, 112, 30);
panelLeft.add(btnForside);
JButton btnDagbog = new JButton("Dagbog");
btnDagbog.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
setCardLayoutView("name_1472176236196000");
}
});
btnDagbog.setCursor(Cursor.getPredefinedCursor(Cursor.HAND_CURSOR));
btnDagbog.setContentAreaFilled(false);
btnDagbog.setBorderPainted(false);
btnDagbog.setBorder(null);
btnDagbog.setFont(new Font("Tahoma", Font.PLAIN, 17));
btnDagbog.setForeground(Color.WHITE);
btnDagbog.setIcon(new ImageIcon(Main.class.getResource("/Images/icons8_Book_32px.png")));
btnDagbog.setBounds(16, 116, 112, 30);
panelLeft.add(btnDagbog);
JButton btnAftaler = new JButton("Aftaler");
btnAftaler.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
setCardLayoutView("name_1472177885026100");
}
});
btnAftaler.setCursor(Cursor.getPredefinedCursor(Cursor.HAND_CURSOR));
btnAftaler.setContentAreaFilled(false);
btnAftaler.setBorderPainted(false);
btnAftaler.setBorder(null);
btnAftaler.setForeground(Color.WHITE);
btnAftaler.setFont(new Font("Tahoma", Font.PLAIN, 17));
btnAftaler.setIcon(new ImageIcon(Main.class.getResource("/Images/icons8_Planner_32px.png")));
btnAftaler.setBounds(16, 173, 112, 30);
panelLeft.add(btnAftaler);
JButton btnKontakt = new JButton("Kontakt");
btnKontakt.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
setCardLayoutView("name_1472179607862700");
}
});
btnKontakt.setCursor(Cursor.getPredefinedCursor(Cursor.HAND_CURSOR));
btnKontakt.setContentAreaFilled(false);
btnKontakt.setBorder(null);
btnKontakt.setBorderPainted(false);
btnKontakt.setFont(new Font("Tahoma", Font.PLAIN, 17));
btnKontakt.setForeground(Color.WHITE);
btnKontakt.setIcon(new ImageIcon(Main.class.getResource("/Images/icons8_Phone_32px.png")));
btnKontakt.setBounds(16, 231, 112, 30);
panelLeft.add(btnKontakt);
JPanel panelTop = new JPanel();
panelTop.addMouseMotionListener(new MouseMotionAdapter() {
@Override
public void mouseDragged(MouseEvent arg0) {
int x = arg0.getXOnScreen(); // makes uggerhøj picture dragable
int y = arg0.getYOnScreen(); // makes uggerhøj picture dragable
Main.this.setLocation(x - xx, y - xy); // makes uggerhøj picture dragable
}
});
panelTop.addMouseListener(new MouseAdapter() {
@Override
public void mousePressed(MouseEvent e) {
xx = e.getX(); // makes uggerhøj picture dragable
xy = e.getY(); // makes uggerhøj picture dragable
}
});
panelTop.setBackground(new Color(51, 51, 51));
panelTop.setBounds(0, 0, 737, 60);
contentPane.add(panelTop);
panelTop.setLayout(null);
JButton btnX = new JButton("X");
btnX.setCursor(Cursor.getPredefinedCursor(Cursor.HAND_CURSOR));
btnX.setRolloverIcon(null);
btnX.setFont(new Font("Tahoma", Font.BOLD, 18));
btnX.setFocusTraversalKeysEnabled(false);
btnX.setFocusPainted(false);
btnX.setBorderPainted(false);
btnX.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
System.exit(0);
}
});
btnX.setContentAreaFilled(false);
btnX.setForeground(SystemColor.activeCaption);
btnX.setBorder(null);
btnX.setBounds(615, 13, 97, 25);
panelTop.add(btnX);
parentPanel = new JPanel();
parentPanel.setBackground(Color.GRAY);
parentPanel.setBounds(148, 54, 569, 405);
contentPane.add(parentPanel);
cardLayoutObject = new CardLayout(0, 0);
parentPanel.setLayout(cardLayoutObject);
parentPanel.add(Forside, "name_1472174211097300");
Forside.setFocusable(false);
JButton btnTest = new JButton("test");
Forside.add(btnTest);
parentPanel.add(Dagbog, "name_1472176236196000");
JLabel lblTest = new JLabel("dagbog");
Dagbog.add(lblTest);
parentPanel.add(Aftaler, "name_1472177885026100");
parentPanel.add(Kontakt, "name_1472179607862700");
}
private CardLayout cardLayoutObject;
private JPanel parentPanel;
private void setCardLayoutView(String viewName) {
cardLayoutObject.show(parentPanel, viewName);
}
}
和快乐的编码^ - ^。