Xamarin android format string onkey pressed

Question

I have this EditText in which I want the user to type a credit card number, so I want to format the string while the user is typing it, I specifically want the string to have a space every 4 numbers, like this:

xxxx xxxx xxxx xxxx

I found that I could use TextWatcher and onKeyUp but I couldn't understand how use it in a EditText, if some one could explain me I would really appreciate it, thanks.

Answer 1

Create a class that implements the ITextWatcher interface. Then add an instance of that class as a text changed listener...

public class CreditCardFormatter : Java.Lang.Object, ITextWatcher
{
    private EditText _editText;
    public CreditCardFormatter(EditText editText)
    {
     _editText = editText;
    }

    public void AfterTextChanged(IEditable s)
    {
    }

    public void BeforeTextChanged(ICharSequence s, int start, int count, int after)
    {
    }

    public void OnTextChanged(ICharSequence s, int start, int before, int count)
    {
    }
}

In your activity.. (or OnCreateView in a fragment)

public override void OnCreate()
{
    // other code..
    myEditText.AddTextChangedListener(new CreditCardFormatter(myEditText));
}

Then use the override methods to reformat the text to show what you need.