如何只允许在jTextField中引入数字？

我试图使用此处显示的示例，但java显示错误消息

“AttributeSet无法解析为类型”

这就是为什么我试图使用另一种只允许数字的方法：

txtUsername.addKeyListener(new MyKeyListener()); public class MyKeyListener extends KeyAdapter{ public void keyPressed(KeyEvent ke){ System.out.println("Key pressed code = "+ke.getKeyCode()); if (ke.getKeyCode()>=48 && ke.getKeyCode()<=57) return true; else return false; } } 

但是当然它没有用，因为keyPressed方法是void 。 那么，为了在textfield中只打印数字怎么办？

Answer 1

在这里检查这段代码片段，这就是你如何通过使用DocumentFilter只允许JTextField中的数字作为最有效的方式：

 import java.awt.*; import javax.swing.*; import javax.swing.text.AbstractDocument; import javax.swing.text.AttributeSet; import javax.swing.text.BadLocationException; import javax.swing.text.DocumentFilter; import javax.swing.text.DocumentFilter.FilterBypass; public class InputInteger { private JTextField tField; private MyDocumentFilter documentFilter; private void displayGUI() { JFrame frame = new JFrame("Input Integer Example"); frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE); JPanel contentPane = new JPanel(); contentPane.setBorder( BorderFactory.createEmptyBorder(5, 5, 5, 5)); tField = new JTextField(10); ((AbstractDocument)tField.getDocument()).setDocumentFilter( new MyDocumentFilter()); contentPane.add(tField); frame.setContentPane(contentPane); frame.pack(); frame.setLocationByPlatform(true); frame.setVisible(true); } public static void main(String[] args) { Runnable runnable = new Runnable() { @Override public void run() { new InputInteger().displayGUI(); } }; EventQueue.invokeLater(runnable); } } class MyDocumentFilter extends DocumentFilter { @Override public void insertString(DocumentFilter.FilterBypass fp , int offset, String string, AttributeSet aset) throws BadLocationException { int len = string.length(); boolean isValidInteger = true; for (int i = 0; i < len; i++) { if (!Character.isDigit(string.charAt(i))) { isValidInteger = false; break; } } if (isValidInteger) super.insertString(fp, offset, string, aset); else Toolkit.getDefaultToolkit().beep(); } @Override public void replace(DocumentFilter.FilterBypass fp, int offset , int length, String string, AttributeSet aset) throws BadLocationException { int len = string.length(); boolean isValidInteger = true; for (int i = 0; i < len; i++) { if (!Character.isDigit(string.charAt(i))) { isValidInteger = false; break; } } if (isValidInteger) super.replace(fp, offset, length, string, aset); else Toolkit.getDefaultToolkit().beep(); } } 

或者可以简单地使用这种方法，如@Carlos Heuberger所给出的

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

Answer 2

我建议使用JFormattedTextField ，方法如下： 如何使用格式化文本字段

Answer 3

尝试这个：

 public void replace(DocumentFilter.FilterBypass fb, int offset, int length, String text, AttributeSet attrs)throws BadLocationException { if(fb.getDocument().getLength() + text.length() > 10) { return; } fb.insertString(offset, text, attrs); } 

代替：

 public void replace(DocumentFilter.FilterBypass fp, int offset , int length, String string, AttributeSet aset) throws BadLocationException { int len = string.length(); boolean isValidInteger = true; for (int i = 0; i < len; i++) { if (!Character.isDigit(string.charAt(i))) { isValidInteger = false; break; } } if (isValidInteger) super.replace(fp, offset, length, string, aset); else Toolkit.getDefaultToolkit().beep(); } 

Answer 4

这就是我用来消耗非数字的方法

 textField.addKeyListener(new KeyAdapter() { public void keyTyped(KeyEvent e) { char c = e.getKeyChar(); if (((c < '0') || (c > '9')) && (c != KeyEvent.VK_BACK_SPACE)) { e.consume(); // consume non-numbers } } });