如何实现documentlistener

我创建了一些文本字段，我想从中使用用户输入。 我已经读过我应该使用documentlistener，但是我认为在正确的位置实现它有一些困难。

在代码中我试图将其实现到文本字段tf1。 输入im应该被解析为double，所以我可以对它进行一些数学计算。

这是我的代码，我试图实现它。

import java.awt.ComponentOrientation; import java.awt.Container; import java.awt.Dimension; import java.awt.GridBagConstraints; import java.awt.GridBagLayout; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import javax.swing.JButton; import javax.swing.JCheckBox; import javax.swing.JFrame; import javax.swing.JLabel; import javax.swing.JScrollPane; import javax.swing.JTable; import javax.swing.JTextField; import javax.swing.event.DocumentEvent; import javax.swing.event.DocumentListener; public class Display { final static boolean shouldFill = true; final static boolean shouldWeightX = true; final static boolean RIGHT_TO_LEFT = false; public static void addComponentsToPane(Container pane) { if (RIGHT_TO_LEFT) { pane.setComponentOrientation(ComponentOrientation.RIGHT_TO_LEFT); } JButton button; JLabel label; pane.setLayout(new GridBagLayout()); GridBagConstraints c = new GridBagConstraints(); if (shouldFill) { //natural height, maximum width c.fill = GridBagConstraints.HORIZONTAL; } if (shouldWeightX) { c.weightx = 0.5; } ... button = new JButton("Value Bet"); c.fill = GridBagConstraints.HORIZONTAL; c.ipady = 0; c.gridx = 0; c.gridy = 1; pane.add(button, c); button.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { //Execute when button is pressed JFrame frame = new JFrame("Value Bet"); frame.setVisible(true); frame.setSize(500,300); GridBagLayout layout = new GridBagLayout(); frame.setLayout(layout); GridBagConstraints c = new GridBagConstraints(); JLabel label; JTextField tf; if (shouldFill) { //natural height, maximum width c.fill = GridBagConstraints.HORIZONTAL; } if (shouldWeightX) { c.weightx = 0.5; } ... final JTextField tf1 = new JTextField(); c.fill = GridBagConstraints.HORIZONTAL; c.gridx = 1; c.gridy = 2; frame.add(tf1, c); tf1.getDocument().addDocumentListener(new DocHandler(){ public class DocHandler implements DocumentListener{ @Override public void changedUpdate(DocumentEvent arg0) { tfHasChanged(); } @Override public void insertUpdate(DocumentEvent arg0) { tfHasChanged(); } @Override public void removeUpdate(DocumentEvent arg0) { tfHasChanged(); } } public void tfHasChanged(){ double chance1 = Double.parseDouble(tf1.getText()); } }); ... div components } private static void createAndShowGUI() { //Create and set up the window. JFrame frame = new JFrame("Betting Application"); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); //Set up the content pane. addComponentsToPane(frame.getContentPane()); //Display the window. frame.pack(); frame.setVisible(true); } public static void main(String[] args) { //Schedule a job for the event-dispatching thread: //creating and showing this application's GUI. javax.swing.SwingUtilities.invokeLater(new Runnable() { public void run() { createAndShowGUI(); } }); } } 

Answer 1

对于Numbers，您必须实现DocumentFilter或直接将JFormattedTextField与Number formatter一起使用

然后可能的方式（块执行）代码行

 formatter.setMinimum(0.0); formatter.setMaximum(1000.00); 

并为textField1添加一些公式，例如textField1等于textField1值，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 static void main(String args[]) { 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(); } private DocumentListenerAdapter() { } } 

Answer 2

如果tf1是一个文本字段，那么Doc​​ument Listener实现了3个方法，如changedUpdate，insertUpdate，removeUpdate

 tf1.getDocument().addDocumentListener(new DocumentListener() { @Override public void changedUpdate(DocumentEvent e){ //do some math tf1.getText(); } @Override public void insertUpdate(DocumentEvent e) { /do some math tf1.getText(); } @Override public void removeUpdate(DocumentEvent e) { // TODO Auto-generated method stub } });