Question

我试图通过点击JButton向现有的JPanel（cardLayout）添加一张新卡，然后转到那张新卡，但由于新卡没有注册，我得到Null异常。

我试过搜索谷歌，但无法找到和示例，我试图使用

'保存'布局

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

但没有任何作用，这可能是动态的吗？如果有的话，有谁知道任何一个例子？

下面的代码，jPanelSliding1.nextSlidPanel只是移动到CardLayout中选定的JPanel。此处创建的新面板在找不到面板时导致空错误。感谢：）

/*
* 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

如果您只是在某些事件上处理更改窗口的卡片，以下情况可能有所帮助。

Oracle Tutorial example

Answer 2

我不确定这是否可行但是：

我看到的是您正在尝试“刷新/重新/验证” jPanelSliding 值。相反，您应修改的是您尝试点击的面板。可以更新jPanelSliding，但是面板（在main上声明）没有被实现。

那么，为什么不尝试对主要声明的面板进行“验证”调用？

你可以尝试并告诉我们它是否有效吗？

Answer 3

找到我的问题的答案，由于某种原因，我必须在创建后命名面板，否则永远找不到它。谢谢您的帮助。

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

Answer 4

我也在处理同样的问题。
经过一些测试，重新测试和很多失败的我的伪算法是这样的：

parentPanel：包含我们要删除的面板
childPanel：我们要切换的面板
parentPanelLayout：parentPanel的布局
editParentLayout（）：每次使用不同的childPanel和NEW parentPanelLayout构建parentPanel

parentPanel.remove(childPanel); 
editParentLayout();
parentPanel.revalidate();
parentPanel.repaint();

Java：在运行时之后将面板添加到现有面板

4 个答案: