javaswingjformattedtextfielddocumentfilter

How to set a Maximum and Minimum value that can be entered in a Jformattedtextfield , using DocumentFilter?


I am newbie to Java programming. I have a document filter that only allow numeric values and decimals with "." in a JFormattedTextField. Now I want to implement a method within that filter, to only allow a maximum and minimum value , like I want whatever the value of number entered, it must be between [0-1], otherwise it should not accept whatever is typed.

Now I don't want to use JSpinner, because from 0 to 1 there is millions of Decimals eg: 0.0001, 0.0012 ...

This is my documentFilter code:

package javagui.views;
import java.text.NumberFormat;
import java.text.ParseException;
import java.util.Locale;

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

public class SeulementNumerique extends PlainDocument  {
    public static final String FLOAT = "0123456789.";
      protected String acceptedChars = null;
      protected boolean negativeAccepted = false;
      public SeulementNumerique() {
        this(FLOAT);
      }
      public SeulementNumerique(String acceptedchars) {  
        acceptedChars = acceptedchars;
      }

      public void setNegativeAccepted(boolean negativeaccepted) {
        if (acceptedChars.equals(FLOAT)) {
          negativeAccepted = negativeaccepted;
          acceptedChars += "-";
        }
      }

      public void insertString(int offset, String str, AttributeSet attr) throws BadLocationException {

        if (str == null)
          return;
        for (int i = 0; i < str.length(); i++) {
          if (acceptedChars.indexOf(str.valueOf(str.charAt(i))) == -1)
            return;
        }
        if (acceptedChars.equals(FLOAT) || (acceptedChars.equals(FLOAT + "-") && negativeAccepted)) {
          if (str.indexOf(".") != -1) {
            if (getText(0, getLength()).indexOf(".") != -1) {
              return;
            }
          }
        }
        if (negativeAccepted && str.indexOf("-") != -1) {
          if (str.indexOf("-") != 0 || offset != 0) {
            return;
          }
        }
        super.insertString(offset, str, attr); 
      }
    }

Now to call for that Filter in my main code I use:

formattedTextField_5 = new JFormattedTextField();
formattedTextField_5.setDocument(new SeulementNumerique());

Is there any simple way to set Maximum and Minimum value that can be entered in a JFormattedTextField?


Solution

  • A JTextField can be used with a custom DocumentFilter that checks values are numeric and within the specified range. Below is a sample DocumentFilter that accomplishes just that:

    public class RestrictedNumberDocumentFilter extends DocumentFilter{
    
        private double min;
        private double max;
    
        public RestrictedNumberDocumentFilter(double min, double max){
            if ( max < min ){
                double temp = max;
                max = min;
                min = temp;
            }
            this.min = min;
            this.max = max;
        }
    
        @Override
        public void insertString(FilterBypass fb, int off, String str, AttributeSet attr) throws BadLocationException {
            StringBuilder sb = new StringBuilder(fb.getDocument().getText(0, fb.getDocument().getLength()));
            if ( test(sb.toString()) ){
                fb.insertString(off, str, attr);
            }else{
                //warn
            }
    
        } 
        @Override
        public void replace(FilterBypass fb, int off, int len, String str, AttributeSet attr)throws BadLocationException{
            StringBuilder sb = new StringBuilder(fb.getDocument().getText(0, fb.getDocument().getLength()));
            sb.replace(off, off+len, str);
            if ( test(sb.toString()) ){
                fb.replace(off, len, str, attr); 
            }else{
                //warn
            }
    
        }
        /**
         * Sanitized the input
         * @param val
         * @return
         */
        private boolean test(String val){
            try{
                double d = Double.parseDouble(val);
                if ( d >= min && d <= max ){
                    return true;
                }
                return false;
            }catch(NumberFormatException e){
                return false;
            }
        }
    }
    

    To use this class, set the DocumentFilter for the Document of the JTextField

    JTextField field = new JTextField();
    AbstractDocument doc =  (AbstractDocument )field.getDocument();
    doc.setDocumentFilter(new RestrictedNumberDocumentFilter (min, max));
    

    You might need to customize this class further for whatever input you anticipate.

    You can do a similar thing with a JFormattedTextField, but it may have its own issues with using a custom DocumentFilter as described here