java - 文本字段使用卡片布局丢弃先前输入的值

Question

我正在使用卡片布局并有 2 个与之关联的面板。一个面板有一个 J 文本字段。我希望在执行以下步骤后，之前在 Jpanel 中输入的值消失:

1. 在 JtextField 中输入内容
2. 转到其他面板
3. 然后返回第一个面板

此外，当我在文本面板上时，我不希望当我失去对文本字段的焦点时文本消失。我怎样才能完成这个行为？

这是一个简单的程序来显示我的问题。

import java.awt.BorderLayout;

public class CardLayoutDemo implements ItemListener
{
JPanel              cards;                                        //a panel that uses CardLayout
final static String BUTTONPANEL = "Card with JButtons";
final static String TEXTPANEL   = "Card with JTextField";

public void addComponentToPane(Container pane)
{
    //Put the JComboBox in a JPanel to get a nicer look.
    JPanel comboBoxPane = new JPanel(); //use FlowLayout
    String comboBoxItems[] = { BUTTONPANEL, TEXTPANEL };
    JComboBox cb = new JComboBox(comboBoxItems);

    cb.setEditable(false);
    cb.addItemListener(this);
    comboBoxPane.add(cb);

    //Create the "cards".
    JPanel card1 = new JPanel();
    card1.add(new JButton("Button 1"));
    card1.add(new JButton("Button 2"));
    card1.add(new JButton("Button 3"));

//my TEst panel----------------------------------------------------------------
    JPanel card2 = new JPanel();
    card2.setLayout(null);
    JLabel lblNewLabel = new JLabel("ncurrency");
    lblNewLabel.setBounds(77, 136, 92, 27);
    card2.add(lblNewLabel);

    //NCurrencyTextField currencyTextField = new NCurrencyTextField();
    JTextField currencyTextField = new JTextField();
    currencyTextField.setBounds(179, 139, 113, 27);
    card2.add(currencyTextField);

    JLabel lblNewLabel_1 = new JLabel("NText field label");
    lblNewLabel_1.setBounds(77, 212, 79, 14);
    card2.add(lblNewLabel_1);

    JTextField textField = new JTextField();
    textField.setBounds(179, 209, 113, 20);
    card2.add(textField);
    textField.setColumns(10);
    //END of my test panel----------------------------------------------------

    //Create the panel that contains the "cards".
    cards = new JPanel(new CardLayout());
    cards.add(card1, BUTTONPANEL);
    cards.add(card2, TEXTPANEL);
    ((CardLayout) cards.getLayout()).show(cards, TEXTPANEL);

    pane.add(comboBoxPane, BorderLayout.PAGE_START);
    pane.add(cards, BorderLayout.CENTER);
}

@Override
public void itemStateChanged(ItemEvent evt)
{
    CardLayout cl = (CardLayout) (cards.getLayout());
    cl.show(cards, (String) evt.getItem());
}

/**
 * Create the GUI and show it. For thread safety, this method should be invoked from the event dispatch thread.
 */
private static void createAndShowGUI()
{
    //Create and set up the window.
    JFrame frame = new JFrame("CardLayoutDemo");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    //Create and set up the content pane.
    CardLayoutDemo demo = new CardLayoutDemo();
    demo.addComponentToPane(frame.getContentPane());

    //Display the window.
    frame.pack();
    frame.setVisible(true);
}

public static void main(String[] args)
{
    /* Use an appropriate Look and Feel */
    try
    {
        //UIManager.setLookAndFeel("com.sun.java.swing.plaf.windows.WindowsLookAndFeel");
        UIManager.setLookAndFeel("javax.swing.plaf.metal.MetalLookAndFeel");
    }
    catch (UnsupportedLookAndFeelException ex)
    {
        ex.printStackTrace();
    }
    catch (IllegalAccessException ex)
    {
        ex.printStackTrace();
    }
    catch (InstantiationException ex)
    {
        ex.printStackTrace();
    }
    catch (ClassNotFoundException ex)
    {
        ex.printStackTrace();
    }
    /* Turn off metal's use of bold fonts */
    UIManager.put("swing.boldMetal", Boolean.FALSE);

    //Schedule a job for the event dispatch thread:
    //creating and showing this application's GUI.
    javax.swing.SwingUtilities.invokeLater(new Runnable()
    {
        @Override
        public void run()
        {
            createAndShowGUI();
        }
    });
}
}

Answer 1

I want the value I previously entered into Jpanel to disappear.

向面板添加一个 ComponentListener 并监听 componentShow(...) 事件以重置文本字段。

while I am on the Text Panel, I don't want the text to disappear when I lost focus to the text field

我没有看到这种行为。一旦我在两个文本字段中的任何一个中输入文本，文本就会保留在那里。

作为一般注释，不要使用空布局。 Swing 被设计为与布局管理器一起使用。