Java：运行后将面板添加到现有面板

Question

我试图通过点击JButton将一张新卡添加到现有的JPanel（cardLayout）中，然后转到该新卡，但由于新卡未注册，我得到了空异常。

我试着在谷歌上搜索，但找不到和示例，我试着用

.validate();
.refresh();
.repaint();

但什么都不管用，这是可能的吗？如果是的话，有人知道任何例子吗？

代码如下，jPanelSliding1。NextSlidePanel只需移动到CardLayout中选定的JPanel。此处创建的新面板由于找不到面板而导致空错误。谢谢：）

/*
* To change this template, choose Tools | Templates
* and open the template in the editor.
*/
package partnerships;

import components.ColorScheme;
import components.Utilities;
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.GridLayout;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import java.beans.PropertyChangeSupport;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;

public class JSlidingPanel extends javax.swing.JPanel implements PropertyChangeListener {

    public PropertyChangeSupport pcs = new PropertyChangeSupport(this);
    private ColorScheme scheme;

    public JSlidingPanel() {
        initComponents();
        pcs.addPropertyChangeListener(this);
        scheme = new ColorScheme();
        Object[][] object = {
            {pcs, "Offered", "BT details", scheme.green()},
            {pcs, "Sold", "BT details", scheme.pink()},
            {pcs, "Other", "BT details", scheme.purple()}
        };

        jPanelSliding1.add(makePanels(object));
    }

    private void setupGUI() {
    }

    private JPanel makePanels(Object[][] objects) {
        JPanel panel = new JPanel();
        panel.setLayout(new GridLayout(0, objects.length));
        for (Object[] properties : objects) {
            panel.add(new ObjectPanel((PropertyChangeSupport) properties[0], properties[1].toString(), properties[2].toString(), (Color) properties[3]));
        }
        return panel;
    }

    private void newPanel(String str) {
        JPanel panel = new JPanel();
        panel.setLayout(new BorderLayout());
        panel.add(new JButton());
        jPanelSliding1.add(panel);

        jPanelSliding1.refresh();
        jPanelSliding1.validate();
        jPanelSliding1.repaint();

        validate();
        repaint();
        Utilities.getTopFrame().pack();
        jPanelSliding1.NextSlidPanel(10, panel);
        jPanelSliding1.refresh();
    }

    @Override
    public void propertyChange(PropertyChangeEvent evt) {
        if (this.isVisible() == true) {
//            makePanels();
            newPanel(evt.getPropertyName());
        }
    }

    public static void main(String args[]) {
        java.awt.EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                JFrame frame = new JFrame();
                JPanel panel = new JPanel();
                JSlidingPanel app = new JSlidingPanel();

                panel.add(app);
                frame.add(panel);
                frame.setDefaultCloseOperation(javax.swing.WindowConstants.DISPOSE_ON_CLOSE);
                frame.setVisible(true);
                frame.pack();
            }
        });
    }

    /**
     * This method is called from within the constructor to initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is always
     * regenerated by the Form Editor.
     */
    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">                         
    private void initComponents() {

        jPanelSliding1 = new apps.JPanelSliding();

        setPreferredSize(new java.awt.Dimension(900, 600));
        setLayout(new java.awt.BorderLayout());

        jPanelSliding1.setLayout(new java.awt.CardLayout());
        add(jPanelSliding1, java.awt.BorderLayout.CENTER);
    }// </editor-fold>                       
    // Variables declaration - do not modify                    
    private apps.JPanelSliding jPanelSliding1;
    // End of variables declaration                  
}

Answer 1

找到了我的问题的答案，出于某种原因，我必须在创建面板后命名，否则就永远找不到它。谢谢你的帮助。

     JPanel panel = new JPanel();
**panel.setName("abc");**
        panel.setLayout(new BorderLayout());

Answer 2

我不确定这是否可行，但：

我看到的是，您正在尝试“刷新/重新绘制/验证”jPanelSliding值。相反，你应该修改的是你试图点击的面板。正在执行，但主面板上可能没有执行。

那么，为什么不尝试对主目录中声明的面板进行“验证”调用呢？

你能试试看它是否管用吗？

Answer 3

如果你只是在处理一些事件中更改窗口的卡片，以下内容可能会有所帮助。

Oracle教程示例