Question

I need a JTextField limiting to 3 decimal places. After a search, i discovered JFormattedTextField, which looks great. The code right now is:

try
{
    double aux = 25.4;
    MaskFormatter mascara = new MaskFormatter("####.###");
    final JFormattedTextField areaTextoXMin = new   JFormattedTextField(mascara);
    areaTextoXMin.setValue(aux);
}
    catch (Exception e)
{
    e.printStackTrace();
}

But if aux is not 4 integer digits and 3 decimal digits, it doesn’t works, and the JFormattedTextField appears empty. Code would work is aux were 1000.000 for example.

Other ideas?

Answer 1

import javax.swing.*;
import javax.swing.text.*;
import java.util.regex.*;
public class MyFilter extends DocumentFilter
{
    public void insertString(DocumentFilter.FilterBypass fb, int offset, String text, AttributeSet attr) throws BadLocationException
    {
        StringBuilder sb = new StringBuilder();
        sb.append(fb.getDocument().getText(0, fb.getDocument().getLength()));
        sb.insert(offset, text);
        if(!containsOnlyNumbers(sb.toString())) return;
        fb.insertString(offset, text, attr);
    }
    public void replace(DocumentFilter.FilterBypass fb, int offset, int length, String text, AttributeSet attr) throws BadLocationException
    {
        StringBuilder sb = new StringBuilder();
        sb.append(fb.getDocument().getText(0, fb.getDocument().getLength()));
        sb.replace(offset, offset + length, text);
        if(!containsOnlyNumbers(sb.toString())) return;
        fb.replace(offset, length, text, attr);
    }
    public boolean containsOnlyNumbers(String text)
    {
        Pattern pattern = Pattern.compile("\\d*(\\.\\d{0,3})?");
        Matcher matcher = pattern.matcher(text);
        boolean isMatch = matcher.matches();
        return isMatch;
    }
}

and then you can use it like:

JTextField txt = new TextField();
DocumentFilter onlyNumberFilter = new MyFilter();
((AbstractDocument)txt.getDocument()).setDocumentFilter(onlyNumberFilter);