如何将JPasswordField限制为4位数？(How to limit JPasswordField to 4 digits? [duplicate])

如何将JPasswordField限制为4位数？(How to limit JPasswordField to 4 digits? [duplicate])

这个问题在这里已有答案：

如何限制Java中JPasswordField的位数？ 3个答案

我刚看到一些问题，但没有一个能解决我的问题。 我有一个JPasswordField ，我需要用户不能在EscPin JPasswordField输入超过4位数字

private void EscPinActionPerformed(java.awt.event.ActionEvent evt) { // TODO add your handling code here: } private javax.swing.JButton Entrar; private javax.swing.JTextField EscNConta; private javax.swing.JPasswordField EscPin; private javax.swing.JLabel Logo; private javax.swing.JLabel NConta; private javax.swing.JLabel Pin; private javax.swing.JButton Sair;

This question already has an answer here:

How to limit the number of digits in a JPasswordField in Java? 3 answers

I just saw some questions here, but none of them resolve the problem for me. I have got a JPasswordField and I need that the user cannot input more than 4 digits in the EscPin JPasswordField

private void EscPinActionPerformed(java.awt.event.ActionEvent evt) { // TODO add your handling code here: } private javax.swing.JButton Entrar; private javax.swing.JTextField EscNConta; private javax.swing.JPasswordField EscPin; private javax.swing.JLabel Logo; private javax.swing.JLabel NConta; private javax.swing.JLabel Pin; private javax.swing.JButton Sair;

最满意答案

您必须获取JPasswordField的内部文档 。 试试这个会起作用。

PlainDocument d=(PlainDocument) jPasswordField1.getDocument(); d.setDocumentFilter(new DocumentFilter(){ @Override public void replace(DocumentFilter.FilterBypass fb, int offset, int length, String text, AttributeSet attrs) throws BadLocationException { String string =fb.getDocument().getText(0, fb.getDocument().getLength())+text; if(string.length() <= 4) super.replace(fb, offset, length, text, attrs); //To change body of generated methods, choose Tools | Templates. } });

You have to get the internal Document of JPasswordField. try this it will work.

PlainDocument d=(PlainDocument) jPasswordField1.getDocument(); d.setDocumentFilter(new DocumentFilter(){ @Override public void replace(DocumentFilter.FilterBypass fb, int offset, int length, String text, AttributeSet attrs) throws BadLocationException { String string =fb.getDocument().getText(0, fb.getDocument().getLength())+text; if(string.length() <= 4) super.replace(fb, offset, length, text, attrs); //To change body of generated methods, choose Tools | Templates. } });