Java TextField getText() returns previous string value

问题

I have a problem with Java Textfield that is when I cover all text in the JTextField and input new text immediately(do not pass backspace) into the JTextField, then I use function getText() I get the previous string not current string. Please help for some solutions. Thanks in advance.

回答1:

I just tested the problem you described by adding a keyListener to a JTextField and printing the getText() method's return value to the console.

What I found out is that it is always one character behind if you want to use the getText() method right in the keyTyped or keyPressed event (I didn't know this because I usually just use a button to confirm I'm done entering the text and bind a KeyEvent to the Return key to trigger the button if a user wants to confirm by hitting enter)

I think this is due to the textField updating its text value AFTER the event is shot.

I assume this is what you did since you didn't provide sample code, so I'll delete this answer if it's not.

The work around to this is to implement what you want to do in the keyReleased method instead.

public void keyReleased(Event e)
{
  System.out.println(myTextField.getText());
}

回答2:

Don't use a KeyListener. The character has NOT been added to the Document when the keyPressed() event is fired.

Add an ActionListener to a JButton. This way the user clicks on the button when text is finised being entered.

Also, in the future post a SSCCE with you question so we can better understand what you are trying to do.

回答3:

for example :

import java.awt.GridLayout;
import javax.swing.*;
import javax.swing.event.DocumentEvent;
import javax.swing.event.DocumentListener;

public class TextLabelMirror {

    private JPanel mainPanel = new JPanel();
    private JTextField field = new JTextField(20);
    private JTextField field1 = new JTextField(20);

    public TextLabelMirror() {
        field.getDocument().addDocumentListener(new DocumentListener() {

            @Override
            public void changedUpdate(DocumentEvent e) {
                updateLabel(e);
            }

            @Override
            public void insertUpdate(DocumentEvent e) {
                updateLabel(e);
            }

            @Override
            public void removeUpdate(DocumentEvent e) {
                updateLabel(e);
            }

            private void updateLabel(DocumentEvent e) {
                java.awt.EventQueue.invokeLater(new Runnable() {

                    @Override
                    public void run() {
                        field1.setText(field.getText());
                    }
                });
            }
        });

        mainPanel.setLayout(new GridLayout(1, 0, 10, 0));
        mainPanel.add(field);
        mainPanel.add(field1);
    }

    public JComponent getComponent() {
        return mainPanel;
    }

    private static void createAndShowUI() {
        JFrame frame = new JFrame("TextLabelMirror");
        frame.getContentPane().add(new TextLabelMirror().getComponent());
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        java.awt.EventQueue.invokeLater(new Runnable() {

            @Override
            public void run() {
                createAndShowUI();
            }
        });
    }
}

来源：https://stackoverflow.com/questions/6591141/java-textfield-gettext-returns-previous-string-value

标签

java

swing

textfield