Allow only selected charcters based on regex in an EditText

Question

I want to allow users only to type certain characters based on the a regex in my android applications. How do I achieve it?

Answer 1

Used a TextWatcher as @Matt Ball suggested.

@Override
public void afterTextChanged(Editable s) {
      String text = s.toString();
      int length = text.length();

      if(length > 0 && !Pattern.matches(PATTERN, text)) {
           s.delete(length - 1, length);
      }
}

Edit Although the TextWatcher works, it would be cleaner to use an InputFilter. Check this example.

Answer 2

Try this: If the character to type matches /[a-zA-Z0-9{insert valid characters here}]/ then allow it, otherwise don't.

Answer 3

You could use android:digits on the xml EditText instead of using a regex.

For your allowed chars of the regex (numbers, comma and plus symbol): android:digits="0123456789,+"

And you could use a string resource as the digits value in case you want to reuse it.