Force JTextField to string value while DocumentFilter only allows digits

问题

I'm working on a Java application and ran into a problem that I cannot seem to solve on my own.

I've set a DocumentFilter on JTextField to only allow digit entries, however, the default values are text. I have a button that resets JTextFields back to default, and it is not working presumingly because of the DocumentFilter.

How can I overcome this problem?

Thanks

回答1:

A field that the user can only enter numeric data into, but also needs to display non-numeric values is contradictive.

Text is supplied to field via the Document, there is no distinction over how that content is generated, either by the user or programmatically.

If you're trying to display a "prompt" in the field, you can could take a look at PromptSupport in SwingLabs SwingX Library

For Example

When the fields have focus, the "prompt" will be hidden, but you can control this, making it shown until the user types something or highlight when focus is gained.

import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import org.jdesktop.swingx.prompt.BuddySupport;
import org.jdesktop.swingx.prompt.PromptSupport;

public class PromptSupportTest {

    public static void main(String[] args) {
        new PromptSupportTest();
    }

    public PromptSupportTest() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                    ex.printStackTrace();
                }

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        public TestPane() {
            JTextField firstName = new JTextField(10);
            PromptSupport.setPrompt("First Name", firstName);
            PromptSupport.setFocusBehavior(PromptSupport.FocusBehavior.HIDE_PROMPT, firstName);

            JTextField lastName = new JTextField(10);
            PromptSupport.setPrompt("Last Name", lastName);
            PromptSupport.setFocusBehavior(PromptSupport.FocusBehavior.HIDE_PROMPT, lastName);

            JTextField picture = new JTextField(10);
            PromptSupport.setPrompt("Picture", picture);
            PromptSupport.setFocusBehavior(PromptSupport.FocusBehavior.HIDE_PROMPT, picture);

            JButton browse = new JButton("...");
            browse.setMargin(new Insets(0, 0, 0, 0));
            browse.setContentAreaFilled(false);
            browse.setFocusPainted(false);
            browse.setFocusable(false);
            browse.setOpaque(false);
            // Add action listener to brose button to show JFileChooser...

            BuddySupport.addRight(browse, picture);

            setLayout(new GridBagLayout());
            GridBagConstraints gbc = new GridBagConstraints();
            gbc.gridwidth = GridBagConstraints.REMAINDER;
            gbc.weightx = 1;

            add(firstName, gbc);
            add(lastName, gbc);
            add(picture, gbc);

            gbc.anchor = GridBagConstraints.CENTER;
            add(new JButton("Ok"), gbc);
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(200, 200);
        }

    }

}

I've also added an example of BuddySupport which is part of the same API, which allows you to "buddy" another component with a text component. Here I've done the classic "file browser" combination, but I do "search" style fields like this all the time...

回答2:

Do one thing:

store the default document some where

final JTextField textField = new JTextField();
final Document defaultDocument=textField.getDocument();

On button click first set the document back to default to disable the validation on textfield and then set the default text

 btn.addActionListener(new ActionListener() {

    @Override
    public void actionPerformed(ActionEvent e) {
        textField.setDocument(defaultDocument);
        textField.setText("hi");
    }
});

Add you document filter back again on focus in the textfield to validate the user inputs.

Please have a look at How to implement in Java ( JTextField class ) to allow entering only digits?.

-- EDIT --

You can do it by adding focus listener on text field.

If the value in text field is empty then set the default value back as a hint. There is no need to do it on button click.

Here is code:

    final JTextField textField = new JTextField("First Name");

    final Document defaultDocument = textField.getDocument();

    final PlainDocument doc = new PlainDocument();
    doc.setDocumentFilter(new DocumentFilter() {
        @Override
        public void insertString(FilterBypass fb, int off, String str, AttributeSet attr)
                throws BadLocationException {
            fb.insertString(off, str.replaceAll("\\D++", ""), attr); // remove
                                                                     // non-digits
        }

        @Override
        public void replace(FilterBypass fb, int off, int len, String str,
                AttributeSet attr) throws BadLocationException {
            fb.replace(off, len, str.replaceAll("\\D++", ""), attr); // remove
                                                                     // non-digits
        }
    });

    textField.addFocusListener(new FocusListener() {

        @Override
        public void focusLost(FocusEvent e) {
            System.out.println("focus lost");
            if(textField.getText() == null || textField.getText().trim().length()==0){
                textField.setDocument(defaultDocument);
                textField.setText("First Name");
            }
        }

        @Override
        public void focusGained(FocusEvent e) {
            System.out.println("focus gained");
            textField.setDocument(doc);
        }
    });