Android: Handle backspace on InputFilter

android, android-edittext, android-input-filter, double

Solution

I solved my problem. Here is the solution in case someone else needs it:

public CharSequence filter(CharSequence source, int start, int end, Spanned dest, int dstart, int dend) {
    if (isValid(dest.toString() + source.toString())) {
        //input is valid
        return null;
    }else{
      //The input is not valid
       if (source.equals("") && dest.toString().length() != 1) {
            //backspace was clicked, do not accept that change, 
            //unless user is deleting the last char
            CharSequence deletedCharacter = dest.subSequence(dstart, dend);
            return deletedCharacter;
        }
        return "";
    }

}

Problem

I created an InputFilter for an EditText component that only allows doubles within a range (e.g. from 1.5 to 5.5). Everything worked fine until I deleted the decimal point: I typed 1.68 and then deleted the decimal point. The value in the text field became 168, which is obviously outside the range. Here is a simplified version of my filter ``` public CharSequence filter(CharSequence source, int start, int end, Spanned dest, int dstart, int dend) { if (isValid(dest.toString() + source.toString())) { //input is valid return null; }else{ //The input is not valid return ""; } } private boolean isValid(String input) { Double inputValue = Double.parseDouble(input); boolean isMinValid = (1.5 <= inputValue); boolean isMaxValid = (5.5 >= inputValue); return isMinValid && isMaxValid; } ```

Original source