如何签约卡片布局

Question

我有一个带有 VerticalLayout (org.jdesktop.swingx.VerticalLayout) 的 ma​​inPanel。主面板有几个子面板。其中之一是根据用户选择动态变化的面板。因此，我将其布局设置为 CardLayout，我认为这是实现这一目标的最简单（也许是最好的？）方式。

我将该面板称为 elasticPanel。顾名思义，它应该是有弹性的。这意味着，它应该能够扩展和收缩。假设它的行为是这样的。如果用户选择1，elasticPanel 应该显示一个，比如JComboBox。如果用户选择2 那么，两个JComboBoxs...

好的，到目前为止它运行良好。现在，当elasticPanel 显示两个JComboBoxs 时，用户再次选择1。我现在需要做的是elasticPanel 应该显示一个JComboBox，它的大小是正常的。但是由于elasticPanel 已经展开，所以会发生什么是它显示JComboBox 被拉伸以适应它的大小。所以它给人一种奇怪的感觉。

---

以下屏幕截图显示了我的界面遇到的问题。

在选择之前。 NONE 被选中。

一个元素被选中

NONE 再次被选中

我需要最后一个屏幕截图中的elasticPanel（故障位置）与第一个屏幕截图中的一样。这只是一个简单的案例。想象一下在显示大约 5、6 个子组件后返回 NONE 时的样子。

我已经尝试过setSize() 方法。它没有做任何事情..那么如何解决这个问题？

感谢任何帮助。谢谢！

Answer 1

很难说你指的是CardLayout 是什么东西。由于CardLayout 以不同的方式工作。你可以做的是简单地放置一个JPanel 说 basePanel 有GridLayout(0, 1) 并将这个JPanel 放在另一个JPanel 上面说 contentPanel，然后现在设置这作为 JFrame 的内容窗格，并在您从视图中添加或删除元素时调用 pack()。这是一个向您展示我的意思的示例。

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

public class ElasticPanel
{
    private JFrame frame;
    private JPanel contentPane;
    private JPanel basePanel;
    /*
     * Array to hold the JComboBox
     * elements.
     */
    private JComboBox[] prodCombo;  
    private JComboBox[] temp;
    /* 
     * Counter to keep track
     * of the number of JComboBox 
     * present.
     */
    private int counter;  
    /*
     * Data for each JComboBox
     */
    private String[] data = {
                                "None",
                                "Sub Category"
                            };

    private ActionListener comboAction =
            new ActionListener()
    {
        @Override
        public void actionPerformed(ActionEvent ae)
        {
            JComboBox cbox = (JComboBox) ae.getSource();
            String command = (String) ae.getActionCommand();
            int index = Integer.parseInt(command);
            String selection = (String) cbox.getSelectedItem();

            if (selection.equals("None"))
            {
                /*
                 * i = index + 1, because, we want to
                 * remove all JComboBox after this one.
                 */
                for (int i = (index + 1); i < prodCombo.length; i++)
                {
                    temp = new JComboBox[prodCombo.length];
                    for (int j = 0; j < prodCombo.length; j++)
                        temp[j] = prodCombo[j];
                    basePanel.remove(prodCombo[i]); 
                }
                prodCombo = new JComboBox[index + 1];
                for (int i = 0; i <= index; i++)
                {                   
                    prodCombo[i] = temp[i];
                }
                counter = prodCombo.length;
                System.out.println("Item Removed\nCounter : " + counter);
            }
            else if (selection.equals("Sub Category"))
            {
                counter++;
                temp = new JComboBox[counter];
                for (int i = 0; i < prodCombo.length; i++)
                {
                    temp[i] = prodCombo[i];
                }
                temp[counter - 1] = new JComboBox(data);
                temp[counter - 1].setActionCommand("" + (counter - 1));
                temp[counter - 1].addActionListener(this);
                prodCombo = new JComboBox[counter];
                for (int i = 0; i < counter; i++)
                    prodCombo[i] = temp[i];
                basePanel.add(prodCombo[counter - 1]);  
                System.out.println("Item Added\nCounter : " + counter);
            }

            //basePanel.revalidate();
            //basePanel.repaint();
            frame.pack();
        }
    };

    public ElasticPanel()
    {
        prodCombo = new JComboBox[1];
        counter = 1;
    }

    private void displayGUI()
    {
        frame = new JFrame("Elastic Panel Example");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        contentPane = new JPanel();

        basePanel = new JPanel(new GridLayout(0, 1, 5, 5));

        prodCombo[counter - 1] = new JComboBox(data);
        prodCombo[counter - 1].setActionCommand("" + (counter - 1));
        prodCombo[counter - 1].addActionListener(comboAction);

        basePanel.add(prodCombo[counter - 1]);
        contentPane.add(basePanel);

        frame.setContentPane(contentPane);
        frame.pack();
        frame.setLocationByPlatform(true);
        frame.setVisible(true);
    }

    public static void main(String... args)
    {
        SwingUtilities.invokeLater(new Runnable()
        {
            @Override
            public void run()
            {
                new ElasticPanel().displayGUI();
            }
        });
    }
}

*最新更新：*

通过添加更多组件并将弹性面板放置在其他位置而不是内容窗格顶部来获得更多洞察力。

import java.awt.*;
import java.awt.event.*;
import java.net.MalformedURLException;
import java.net.URL;
import javax.swing.*;

public class VirtualViewGUI extends JFrame
{
    private JPanel rightPanel;
    private ElasticPanel elasticPanel;

    public VirtualViewGUI()
    {
        super("Virtual View");

        JMenuBar jmenuBar = new JMenuBar();
        JMenu fileMenu = new JMenu("File");
        JMenu helpMenu = new JMenu("Help");
        JMenu feel = new JMenu("Look & Feel");

        JMenu layOutMenu = new JMenu("ConfigureCells");
        JMenuItem add_files = new JMenuItem("Select Directory.."); 
        JMenuItem minCellSize = new JMenuItem("height 260 X  width 260"); 
        JMenuItem moderateCellSize = new JMenuItem("height 320 X  width 320"); 
        JMenuItem maxCellSize = new JMenuItem("height 360 X  width 360"); 
        JMenuItem exit = new JMenuItem("Exit");
        JMenuItem help = new JMenuItem("Help Content");

        fileMenu.add(add_files);
        fileMenu.add(exit);
        layOutMenu.add(minCellSize);
        layOutMenu.add(moderateCellSize);
        layOutMenu.add(maxCellSize);
        helpMenu.add(help);

        jmenuBar.add(fileMenu);
        jmenuBar.add(layOutMenu);
        jmenuBar.add(helpMenu);

        ImageIcon myImage = null;
        try
        {
            myImage = new ImageIcon(
                new URL("http://gagandeepbali.uk.to/" + 
                        "gaganisonline/images/swing/" + 
                        "stackoverflow/cow-cartoon.jpg"));
        }
        catch(MalformedURLException mue)    
        {
            mue.printStackTrace();
        }

        JLabel icon = new JLabel(myImage);
        icon.setIcon(myImage);
        setJMenuBar(jmenuBar); 

        rightPanel = new JPanel();
        elasticPanel = new ElasticPanel(this);
        rightPanel.add(elasticPanel);

        JPanel contentPane = new JPanel();
        contentPane.setLayout(new BorderLayout(5, 5));
        contentPane.add(icon, BorderLayout.CENTER);
        contentPane.add(rightPanel, BorderLayout.LINE_END);

        setContentPane(contentPane);
        pack();
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setLocationByPlatform(true);    
        setVisible(true);
        System.out.println("File Separator is : " + System.getProperty("file.separator"));
    }

    public static void main(String... args)
    {
        SwingUtilities.invokeLater(new Runnable()
        {
            @Override
            public void run()
            {
                new VirtualViewGUI();
            }
        });
    }
}

class ElasticPanel extends JPanel
{
    private JFrame frame;
    private JPanel contentPane;
    /*
     * Array to hold the JComboBox
     * elements.
     */
    private JComboBox[] prodCombo;  
    private JComboBox[] temp;
    /* 
     * Counter to keep track
     * of the number of JComboBox 
     * present.
     */
    private int counter;  
    /*
     * Data for each JComboBox
     */
    private String[] data = {
                                "None",
                                "Sub Category"
                            };

    private ActionListener comboAction =
            new ActionListener()
    {
        @Override
        public void actionPerformed(ActionEvent ae)
        {
            JComboBox cbox = (JComboBox) ae.getSource();
            String command = (String) ae.getActionCommand();
            int index = Integer.parseInt(command);
            String selection = (String) cbox.getSelectedItem();

            if (selection.equals("None"))
            {
                /*
                 * i = index + 1, because, we want to
                 * remove all JComboBox after this one.
                 */
                for (int i = (index + 1); i < prodCombo.length; i++)
                {
                    temp = new JComboBox[prodCombo.length];
                    for (int j = 0; j < prodCombo.length; j++)
                        temp[j] = prodCombo[j];
                    remove(prodCombo[i]);   
                }
                prodCombo = new JComboBox[index + 1];
                for (int i = 0; i <= index; i++)
                {                   
                    prodCombo[i] = temp[i];
                }
                counter = prodCombo.length;
                System.out.println("Item Removed\nCounter : " + counter);
            }
            else if (selection.equals("Sub Category"))
            {
                counter++;
                temp = new JComboBox[counter];
                for (int i = 0; i < prodCombo.length; i++)
                {
                    temp[i] = prodCombo[i];
                }
                temp[counter - 1] = new JComboBox(data);
                temp[counter - 1].setActionCommand("" + (counter - 1));
                temp[counter - 1].addActionListener(this);
                prodCombo = new JComboBox[counter];
                for (int i = 0; i < counter; i++)
                    prodCombo[i] = temp[i];
                add(prodCombo[counter - 1]);    
                System.out.println("Item Added\nCounter : " + counter);
            }

            //revalidate();
            //repaint();
            frame.pack();
        }
    };

    public ElasticPanel(JFrame frame)
    {
        this.frame = frame;
        prodCombo = new JComboBox[1];
        counter = 1;

        setLayout(new GridLayout(0, 1, 5, 5));

        prodCombo[counter - 1] = new JComboBox(data);
        prodCombo[counter - 1].setActionCommand("" + (counter - 1));
        prodCombo[counter - 1].addActionListener(comboAction);

        add(prodCombo[counter - 1]);        
    }
}

Answer 2

如果我理解正确，您有 2 个不同的面板，您可以使用 CardLayout 在这两个面板之间切换。 CardLayout 的问题在于它占用了最大面板的大小。

因此，使用CardLayout，您将无法缩小容器的大小，但您可以通过使用BorderLayout 将面板包裹在另一个面板内并将面板放入BorderLayout.NORTH