Only numbers and one decimal point allow on jtextfield in java [duplicate]

问题

This question already has answers here:

Is there any way to accept only numeric values in a JTextField? (19 answers)

JFormattedTextField for Double still takes characters [duplicate] (2 answers)

Closed 6 years ago.

Have a jtextfield in my java form. I want to not allow to type alpha(Characters) and only allow to type numbers.
And can't type 2 decimal point and two numbers after the decimal point.(that jtextfield for price..)

Please tell me how to do this step by step.

回答1:

Use JFormattedTextField with NumberFormat (See for example). Alternatively you can add your own DocumentFilter to the document of your JTextField

回答2:

Please tell me how to do this step by step.

use JFormattedTextField with NumberFormatter
- restrict number of decimal places
- set various RoundingModes
- restrict range, set minimal and/or maximal value
another of ways is to use JSpinner with SPinnerNUmberModel, but required to use DocumentFilter

for example

import java.awt.*;
import java.awt.font.TextAttribute;
import java.math.*;
import java.text.*;
import java.util.Map;
import javax.swing.*;
import javax.swing.JFormattedTextField.*;
import javax.swing.event.*;
import javax.swing.text.InternationalFormatter;

public class DocumentListenerAdapter {

    public DocumentListenerAdapter() {
        JFrame frame = new JFrame("AbstractTextField Test");
        final JFormattedTextField textField1 = new JFormattedTextField(new Float(10.01));
        textField1.setFormatterFactory(new AbstractFormatterFactory() {
            @Override
            public AbstractFormatter getFormatter(JFormattedTextField tf) {
                NumberFormat format = DecimalFormat.getInstance();
                format.setMinimumFractionDigits(2);
                format.setMaximumFractionDigits(2);
                format.setRoundingMode(RoundingMode.HALF_UP);
                InternationalFormatter formatter = new InternationalFormatter(format);
                formatter.setAllowsInvalid(false);
                //formatter.setMinimum(0.0);
                //formatter.setMaximum(1000.00);
                return formatter;
            }
        });
        final Map attributes = (new Font("Serif", Font.BOLD, 16)).getAttributes();
        attributes.put(TextAttribute.STRIKETHROUGH, TextAttribute.STRIKETHROUGH_ON);
        final JFormattedTextField textField2 = new JFormattedTextField(new Float(10.01));
        textField2.setFormatterFactory(new AbstractFormatterFactory() {
            @Override
            public AbstractFormatter getFormatter(JFormattedTextField tf) {
                NumberFormat format = DecimalFormat.getInstance();
                format.setMinimumFractionDigits(2);
                format.setMaximumFractionDigits(2);
                format.setRoundingMode(RoundingMode.HALF_UP);
                InternationalFormatter formatter = new InternationalFormatter(format);
                formatter.setAllowsInvalid(false);
                //formatter.setMinimum(0.0);
                //formatter.setMaximum(1000.00);
                return formatter;
            }
        });
        textField2.getDocument().addDocumentListener(new DocumentListener() {
            @Override
            public void changedUpdate(DocumentEvent documentEvent) {
                printIt(documentEvent);
            }

            @Override
            public void insertUpdate(DocumentEvent documentEvent) {
                printIt(documentEvent);
            }

            @Override
            public void removeUpdate(DocumentEvent documentEvent) {
                printIt(documentEvent);
            }

            private void printIt(DocumentEvent documentEvent) {
                DocumentEvent.EventType type = documentEvent.getType();
                double t1a1 = (((Number) textField2.getValue()).doubleValue());
                if (t1a1 > 1000) {
                    Runnable doRun = new Runnable() {
                        @Override
                        public void run() {
                            textField2.setFont(new Font(attributes));
                            textField2.setForeground(Color.red);
                        }
                    };
                    SwingUtilities.invokeLater(doRun);
                } else {
                    Runnable doRun = new Runnable() {
                        @Override
                        public void run() {
                            textField2.setFont(new Font("Serif", Font.BOLD, 16));
                            textField2.setForeground(Color.black);
                        }
                    };
                    SwingUtilities.invokeLater(doRun);
                }
            }
        });
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.add(textField1, BorderLayout.NORTH);
        frame.add(textField2, BorderLayout.SOUTH);
        frame.setVisible(true);
        frame.pack();
    }

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

            @Override
            public void run() {
                DocumentListenerAdapter main = new DocumentListenerAdapter();
            }
        });
    }
}

回答3:

Try this code if you want only number to be inputed in you textfield

txtfield.addKeyListener(new java.awt.event.KeyAdapter() {
    public void keyTyped(KeyEvent e) {
        char c = e.getKeyChar();
        if (!((c >= 0) && (c <= 9) || (c == KeyEvent.VK_BACK_SPACE) || (c == KeyEvent.VK_DELETE))) {
            getToolkit().beep();
            e.consume();
        }
    }
});

paste the above code in your constructor after txtfield initialization

also take a look at this stuff JFormattedTextField for Double still takes characters

来源：https://stackoverflow.com/questions/18102740/only-numbers-and-one-decimal-point-allow-on-jtextfield-in-java

标签

java

swing

numbers

filtering

jtextfield