Limiting the Number of Characters in a Jtextfield

How To limit the number of characters in JTextField?

http://www.rgagnon.com/javadetails/java-0198.html

import javax.swing.text.PlainDocument;
import javax.swing.text.AttributeSet;
import javax.swing.text.BadLocationException;

public class JTextFieldLimit extends PlainDocument {
  private int limit;

  JTextFieldLimit(int limit) {
   super();
   this.limit = limit;
   }

  public void insertString( int offset, String  str, AttributeSet attr ) throws BadLocationException {
    if (str == null) return;

    if ((getLength() + str.length()) <= limit) {
      super.insertString(offset, str, attr);
    }
  }
}

Then

import java.awt.*;
import javax.swing.*;

 public class DemoJTextFieldWithLimit extends JApplet{
   JTextField textfield1;
   JLabel label1;

   public void init() {
     getContentPane().setLayout(new FlowLayout());
     //
     label1 = new JLabel("max 10 chars");
     textfield1 = new JTextField(15);
     getContentPane().add(label1);
     getContentPane().add(textfield1);
     textfield1.setDocument
        (new JTextFieldLimit(10));
     }
}

(first result from google)

Limit number of characters in JTextField

JFormattedTextField leads to evil UIs.

The class you want is javax.swing.text.DocumentFilter. This allows you modify mutations in a chain-of-command style.

JTextField: How to limit the number of characters?

simply change your current remove method:

 @Override  
 public void remove(DocumentFilter.FilterBypass fb, int offset, int length) throws BadLocationException 
 {  

     fb.insertString(offset, "", null);
 } 

for this one:

 @Override  
 public void remove(DocumentFilter.FilterBypass fb, int offset, int length) throws BadLocationException 
 {  
     fb.remove(offset, length);
 }

it should now work.

How to restrict the JTextField to a x number of characters

You should use a DocumentFilter as per this tutorial. For example:

import javax.swing.*;
import javax.swing.text.*;

public class JTextFieldLimit2 extends JPanel{
   JTextField textfield = new JTextField(5);

   public JTextFieldLimit2() {
      PlainDocument doc = (PlainDocument) textfield.getDocument();
      doc.setDocumentFilter(new TextLengthDocFilter(3));

      add(textfield);
   }

   private class TextLengthDocFilter extends DocumentFilter {
      private int maxTextLength;

      public TextLengthDocFilter(int maxTextLength) {
         this.maxTextLength = maxTextLength;
      }

      private boolean verifyText(String text) {
         return text.length() <= maxTextLength;
      }

      @Override
      public void insertString(FilterBypass fb, int offset, String string,
               AttributeSet attr) throws BadLocationException {

         Document doc = fb.getDocument();
         String oldText = doc.getText(0, doc.getLength());
         StringBuilder sb = new StringBuilder(oldText);
         sb.insert(offset, string);

         if (verifyText(sb.toString())) {
            super.insertString(fb, offset, string, attr);
         }

      }

      @Override
      public void replace(FilterBypass fb, int offset, int length, String text, AttributeSet attrs)
               throws BadLocationException {
         Document doc = fb.getDocument();
         String oldText = doc.getText(0, doc.getLength());
         StringBuilder sb = new StringBuilder(oldText);

         sb.replace(offset, offset + length, text);
         if (verifyText(sb.toString())) {
            super.replace(fb, offset, length, text, attrs);
         }
      }

      @Override
      public void remove(FilterBypass fb, int offset, int length) throws BadLocationException {
         Document doc = fb.getDocument();
         String oldText = doc.getText(0, doc.getLength());
         StringBuilder sb = new StringBuilder(oldText);

         sb.replace(offset, offset + length, "");

         if (verifyText(sb.toString())) {
            super.remove(fb, offset, length);            
         }
      }
   }

   private static void createAndShowUI() {
      JFrame frame = new JFrame("JTextFieldLimit2");
      frame.getContentPane().add(new JTextFieldLimit2());
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.pack();
      frame.setLocationRelativeTo(null);
      frame.setVisible(true);
   }

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

Limit character input in jtextfield or area

I would use javax.swing.text.Document

You can initiate it like:

 public static Document createTextDocument(int maxLength){
        return new TextDocument(maxLength);
    }

...

Document document = createTextDocument(5); // limit to 5 chars
textField1.setDocument(document);

document = createTextDocument(10); // limit to 10 chars
textField2.setDocument(document);

Here is custom TextDocument class:

public class TextDocument extends PlainDocument{

    private static final long serialVersionUID = 1L;
    private int maxLength = Integer.MAX_VALUE;

    TextDocument(){}
    TextDocument(int maxlength){this.maxLength=maxlength;}

     public void setMaxLength(int maxLength) {
            if (maxLength < 0)
                throw new IllegalArgumentException("maxLength<0");
            this.maxLength = maxLength;
        }

     public void insertString(int offset, String str, AttributeSet attr)
     throws BadLocationException {
         if (validateLength(offset, str) == false)
                return;

            super.insertString(offset, str, attr);
     }

     private boolean validateLength(int offset, String toAdd) {
            String str_temp;
            //String str_text = "";
            String str1 = "";
            String str2 = "";
            try {
                str1 = getText(0, offset);
                str2 = getText(offset, getLength() - offset);
            } catch (Exception e) {
                e.printStackTrace();
            }

            str_temp = str1 + toAdd + str2;
            if (maxLength < str_temp.length()) {
                beep();
                return false;
            } else
                return true;

        }

        private void beep() {
            java.awt.Toolkit.getDefaultToolkit().beep();
        }
}

Hope it will help

---

Related Topics