java中的jtextfield只允许数字和一个小数点

Only numbers and one decimal point allow on jtextfield in java

提问by Gayan Weerakkodi

1. Have a jtextfieldin my java form. I want to not allow to type alpha(Characters) and only allow to type numbers.

2. And can't type 2 decimal point and two numbers after the decimal point.(that jtextfieldfor price..)

1. jtextfield在我的 java 表单中有一个。我不想允许输入 alpha(Characters) 而只允许输入数字。

2. 并且不能输入2个小数点和小数点后的两个数字。（jtextfield价格..）

Please tell me how to do this step by step.

请告诉我如何一步一步地做到这一点。

回答by Nidhish Krishnan

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

如果您只想输入数字，请尝试使用此代码 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 txtfieldinitialization

txtfield初始化后将上述代码粘贴到您的构造函数中

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

也看看这个东西JFormattedTextField for Double 仍然需要字符

回答by StanislavL

Use JFormattedTextFieldwith NumberFormat (See for example). Alternatively you can add your own DocumentFilterto the document of your JTextField

JFormattedTextField与 NumberFormat 一起使用（参见示例）。或者，您可以将自己的添加到您DocumentFilter的文档中JTextField

回答by mKorbel

Please tell me how to do this step by step.

请告诉我如何一步一步地做到这一点。

1. use JFormattedTextField with NumberFormatter

   • restrict number of decimal places

   • set various RoundingModes

   • restrict range, set minimal and/or maximal value

2. another of ways is to use JSpinner with SPinnerNUmberModel, but required to use DocumentFilter

1. 将 JFormattedTextField 与 NumberFormatter 一起使用

   • 限制小数位数

   • 设置各种 RoundingModes

   • 限制范围，设置最小值和/或最大值

2. 另一种方法是将 JSpinner 与 SPinnerNUMberModel 一起使用，但需要使用 DocumentFilter

for example

例如

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();
            }
        });
    }
}