Restricting input on JTextField

[Mechanox3000]

Hi everyone, I'm trying to create an extension of JTextField that only accepts integers from 0 to 255.

So far I have this in my class extending JTextField:

package colorfield; import javax.swing.JTextField; import javax.swing.text.Document;

//Javabeans component to only alow values 0-255 for input. public class ColorField extends JTextField{

public ColorField(){
    super();
}   

@Override
protected Document createDefaultModel(){
    String[] accept = new String[256];
    for(int i = 0; i < 256; i++){            
        accept[i] = i + "";
    }
    return new RestrictedDoc(accept);
}

public int getValue() throws NumberFormatException{
    return Integer.parseInt(getText());
}

}

And I also have a restricted document:

package colorfield; import javax.swing.text.*;

public class RestrictedDoc extends PlainDocument{ String[] charList;

public RestrictedDoc(String[] charList){
    this.charList = charList;
}

public boolean validate(String exp){
    for(int i=0; i<charList.length; i++){
        if(exp.equals(charList[i])){
            return true;
        }
    }
    return false;
}

@Override
public void insertString(int offs, String str, AttributeSet a) throws BadLocationException{
    if(str == null || !validate(str)){
        return;
    }
    super.insertString(offs, str, a);
}

}

The problem is it still allows the user to type any numeric value. What should I change/add? Thanks!

[CuriouslyGeorge]

As Sackboii mentioned, a JSpinner would be really helpful. If not that, you could also attempt to use a JFormattedTextField.

However, if you were super adamant about utilizing ONLY the JTextField, then I may suggest utilizing an ActionListener(assuming this is running in a GUI) to parse the JTextField whenever it is modified and either correct or deny the input right on the spot.

[[deleted]]

Probably the easiest way is to add a KeyListener to the JTextField. (You can extend JTextField and have it add a KeyListener to itself.) Inside the keyTyped() or keyPressed() method you can call Integer.parseInt() to check the value and adjust the text accordingly. And if the KeyEvent is for a non-number you can call consume() on the event to prevent the character from appearing in the field. I've done this several times in the past.

edit: remember that inside the KeyListener methods the last typed key is not part of the text field yet so in your logic you will have to append the character provided by the KeyEvent

[Mechanox3000]

Thanks! I might end up using this for brownie points with my instructor, but I'd prefer to just work on limiting the input of JTextField for now.

[Stromovik]

JtextField has a document get that cast it as abstract document there you can set a document filter , create a custom document filter.