文本字段使用卡布局放棄先前輸入的值

Question

我正在使用卡片布局，並且有2個面板與其關聯。 一個面板具有J文本字段。 在執行以下步驟之后，我希望以前輸入到Jpanel中的值消失：

1. 在JtextField中輸入內容
2. 轉到另一個面板
3. 然后回到第一個面板

另外，當我在“文本面板”上時，當我失去對文本字段的關注時，我也不希望文本消失。 我怎樣才能做到這一點？

這是一個顯示我的問題的簡單程序。

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

我希望以前輸入Jpanel的值消失。

將ComponentListener添加到面板中，並偵聽componentShow(...)事件以重置文本字段。

當我在“文本面板”上時，當我失去對文本字段的關注時，我不希望文本消失

我沒有看到這種行為。 在兩個文本字段之一中輸入文本后，文本將保留在那里。

作為一般性評論，請勿使用空布局。 Swing旨在與布局管理器一起使用。

Answer 2

您可以舍棄這樣的值：

panel.remove();
revalidate();
repaint();

因此，在mouseClick上或您認為合適的任何方法上，都可以嘗試上述方法。

Answer 3

如下更改您的itemStateChanged(ItemEvent evt)

public void itemStateChanged(ItemEvent evt)
{
    CardLayout cl = (CardLayout) (cards.getLayout());
    cl.show(cards, (String) evt.getItem());
    currencyTextField.setText("");
    textField.setText("");
}

同樣不要忘記將JTextField聲明為全局

完整代碼：

import java.awt.*;
import java.awt.event.*;

import javax.swing.*;

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";
    JTextField currencyTextField;
    JTextField textField;

    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();
        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);

        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);
    }

    public void itemStateChanged(ItemEvent evt) {
        CardLayout cl = (CardLayout) (cards.getLayout());
        cl.show(cards, (String) evt.getItem());
        currencyTextField.setText("");
        textField.setText("");
    }

    /**
     * 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() {
            public void run() {
                createAndShowGUI();
            }
        });
    }
}