How do I use InputFilter to limit characters in an EditText in Android?

I found this on another forum. Works like a champ.

InputFilter filter = new InputFilter() {
    public CharSequence filter(CharSequence source, int start, int end,
            Spanned dest, int dstart, int dend) {
        for (int i = start; i < end; i++) {
            if (!Character.isLetterOrDigit(source.charAt(i))) {
                return "";
            }
        }
        return null;
    }
};
edit.setFilters(new InputFilter[] { filter });

much easier:

<EditText
    android:inputType="text"
    android:digits="0,1,2,3,4,5,6,7,8,9,*,qwertzuiopasdfghjklyxcvbnm" />

InputFilters are a little complicated in Android versions that display dictionary suggestions. You sometimes get a SpannableStringBuilder, sometimes a plain String in the source parameter.

The following InputFilter should work. Feel free to improve this code!

new InputFilter() {
    @Override
    public CharSequence filter(CharSequence source, int start, int end,
            Spanned dest, int dstart, int dend) {

        if (source instanceof SpannableStringBuilder) {
            SpannableStringBuilder sourceAsSpannableBuilder = (SpannableStringBuilder)source;
            for (int i = end - 1; i >= start; i--) { 
                char currentChar = source.charAt(i);
                 if (!Character.isLetterOrDigit(currentChar) && !Character.isSpaceChar(currentChar)) {    
                     sourceAsSpannableBuilder.delete(i, i+1);
                 }     
            }
            return source;
        } else {
            StringBuilder filteredStringBuilder = new StringBuilder();
            for (int i = start; i < end; i++) { 
                char currentChar = source.charAt(i);
                if (Character.isLetterOrDigit(currentChar) || Character.isSpaceChar(currentChar)) {    
                    filteredStringBuilder.append(currentChar);
                }     
            }
            return filteredStringBuilder.toString();
        }
    }
}