如何在按下按钮时添加来自不同 class 的面板

Question

我想在 "menuPan" class 中按下 "drop" 按钮时从 "newWork" class 添加面板。我无法添加面板。简单说明如何在按下按钮时从不同的 class 添加面板。这是三个不同的 classes 。主要Class :-

public class userFrame  extends JFrame{

 public void Frame() 
    {
    setTitle("TEST CASE");
    setSize(900,670);

    add(new MenuPan(),BorderLayout.NORTH);
    add(new WorkPan(),BorderLayout.CENTER);


    setLocationRelativeTo(this);
    setVisible(true);
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

}
public static void main(String [] args){
    userFrame u =new userFrame();
    u.Frame();
}
}

菜单面板

public class MenuPan  extends JPanel implements ActionListener{
WorkPan work=new WorkPan();
JButton view;
public menuPan() {
    setBackground(Color.white);
    setBorder(BorderFactory.createLineBorder(Color.LIGHT_GRAY));
    setLayout(new FlowLayout(1, 15, 10));
    view=new JButton(" Registered Courses ");
    view.addActionListener(this);
    add(view);
}
@Override
public void actionPerformed(ActionEvent e) {
    work.TaskPannel();
}
}

工作PAN class :-

 class WorkPan extends JPanel{
   JPanel work=new JPanel();
   public WorkPan() {
     setBackground(Color.LIGHT_GRAY);
     setLayout(new BorderLayout(40, 50));

   }

   void TaskPannel() {
      System.out.println("here");
      add(new NewWork(),BorderLayout.CENTER);// adds NewWork panel 
   }
}

新作品Class

  class NewWork extends JPanel{

  public NewWork(){

     setBackground(Color.red);       

  }
  }

Answer 1

一个问题 -- 您创建了一个 workPan（应重命名为 WorkPan），在 ActionListener 中更改其状态，但从未将其添加到 GUI 中。因此，您似乎正在更改未显示的 GUI 组件的状态，因此 GUI 中不会显示任何内容是有道理的。

建议：

确保只创建一个 WorkPan 引用，
确保在 GUI 中显示此单个引用
确保您的 ActionListener 在 相同的引用.

侧面推荐：

学习并遵循 Java 命名约定，以便其他人可以更轻松地理解和遵循您的代码。
要在 GUI 中交换 JPanel，我强烈建议您使用 CardLayout，而不是像您目前所做的那样手动添加和删除组件。请查看 CardLayout Tutorial.

我的解决方案确实有效，但您还必须调用 revalidate 和 repaint 以使 GUI 布局新组件并重新绘制它。注意 \ !! 评论

标记的添加和更改

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class FooWork {
    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> {
            userFrame.main(args);
        });
    }
}

class NewWork extends JPanel {
    public NewWork() {
        setBackground(Color.red);
    }
}

class WorkPan extends JPanel {
    JPanel work = new JPanel();

    public WorkPan() {
        setBackground(Color.LIGHT_GRAY);
        setLayout(new BorderLayout(40, 50));
    }

    void TaskPannel() {
        System.out.println("here");
        add(new NewWork(), BorderLayout.CENTER);// adds NewWork panel

        // !!
        revalidate();
        repaint();
        // !!
    }
}

class MenuPan extends JPanel implements ActionListener {
    // !! WorkPan work = new WorkPan();
    WorkPan work; // !!
    JButton view; // !!

    // !!
    public MenuPan(WorkPan workPan) { // references are key

        // !!
        this.work = workPan; // set the reference!
        // !!

        setBackground(Color.white);
        setBorder(BorderFactory.createLineBorder(Color.LIGHT_GRAY));
        setLayout(new FlowLayout(1, 15, 10));
        view = new JButton(" Registered Courses ");
        view.addActionListener(this);
        add(view);
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        work.TaskPannel();
    }
}

class userFrame extends JFrame {
    public void Frame() {
        setTitle("TEST CASE");
        setSize(900, 670);

        // !!
        WorkPan workPan = new WorkPan();
        MenuPan menuPan = new MenuPan(workPan);
        // !!

        // !!
        // add(new MenuPan(), BorderLayout.NORTH);
        // add(new WorkPan(), BorderLayout.CENTER);
        add(menuPan, BorderLayout.NORTH);
        add(workPan, BorderLayout.CENTER);
        // !!

        setLocationRelativeTo(this);
        setVisible(true);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }

    public static void main(String[] args) {
        userFrame u = new userFrame();
        u.Frame();
    }
}

但是，更清洁的方法是使用 CardLayout 来帮助进行交换：

import java.awt.BorderLayout;
import java.awt.CardLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.event.ActionEvent;
import java.awt.event.KeyEvent;

import javax.swing.*;

public class SwapStuff {
    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> createAndShowGui());
    }

    private static void createAndShowGui() {
        SwapMainPanel mainPanel = new SwapMainPanel();
        JFrame frame = new JFrame("SwapStuff");
        frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
        frame.add(mainPanel);
        frame.pack();
        frame.setLocationByPlatform(true);
        frame.setVisible(true);
    }
}

class SwapMainPanel extends JPanel {
    private CardLayout cardLayout = new CardLayout();
    private JPanel cardPanel = new JPanel(cardLayout);
    private ButtonPanel buttonPanel = new ButtonPanel(this); // pass the reference
    private WorkPanel workPanel = new WorkPanel();
    private ViewPanel viewPanel = new ViewPanel();

    public SwapMainPanel() {
        cardPanel.add(workPanel, workPanel.getClass().getName());
        cardPanel.add(viewPanel, viewPanel.getClass().getName());

        setLayout(new BorderLayout());
        add(buttonPanel, BorderLayout.PAGE_START);
        add(cardPanel, BorderLayout.CENTER);
    }

    // one possible way to swap "cards"
    public void nextCard() {
        cardLayout.next(cardPanel);
    }
}

class ButtonPanel extends JPanel {
    private SwapMainPanel mainPanel;

    public ButtonPanel(SwapMainPanel mainPanel) {
        this.mainPanel = mainPanel;  // set the reference!
        add(new JButton(new SwapAction("Swap Panels", KeyEvent.VK_S)));
    }

    private class SwapAction extends AbstractAction {
        public SwapAction(String name, int mnemonic) {
            super(name);
            putValue(MNEMONIC_KEY, mnemonic);
        }

        @Override
        public void actionPerformed(ActionEvent e) {
            mainPanel.nextCard();
        }
    }
}

class WorkPanel extends JPanel {
    public WorkPanel() {
        setBorder(BorderFactory.createTitledBorder("Work Panel"));
    }

    @Override
    public Dimension getPreferredSize() {
        return new Dimension(500, 400);
    }
}

class ViewPanel extends JPanel {
    public ViewPanel() {
        setBorder(BorderFactory.createTitledBorder("View Panel"));
        setBackground(Color.RED);
    }

    @Override
    public Dimension getPreferredSize() {
        return new Dimension(500, 400);
    }
}

如何在按下按钮时添加来自不同 class 的面板

how to add Panel from different class on pressing button

java

swing

jpanel