Validation date in EditText for android while user is clicking

EditTextDateValidation.java

//SOURCE: http://stackoverflow.com/questions/16889502/how-to-mask-an-edittext-to-show-the-dd-mm-yyyy-date-format




EditText date;
date = (EditText)findViewById(R.id.whichdate);
date.addTextChangedListener(tw);
TextWatcher tw = new TextWatcher() {
    private String current = "";
    private String ddmmyyyy = "DDMMYYYY";
    private Calendar cal = Calendar.getInstance();
When user changes text of the EditText

    @Override
    public void onTextChanged(CharSequence s, int start, int before, int count) {
        if (!s.toString().equals(current)) {
            String clean = s.toString().replaceAll("[^\\d.]", "");
            String cleanC = current.replaceAll("[^\\d.]", "");

            int cl = clean.length();
            int sel = cl;
            for (int i = 2; i <= cl && i < 6; i += 2) {
                sel++;
            }
            //Fix for pressing delete next to a forward slash
            if (clean.equals(cleanC)) sel--;

            if (clean.length() < 8){
               clean = clean + ddmmyyyy.substring(clean.length());
            }else{
               //This part makes sure that when we finish entering numbers
               //the date is correct, fixing it otherwise
               int day  = Integer.parseInt(clean.substring(0,2));
               int mon  = Integer.parseInt(clean.substring(2,4));
               int year = Integer.parseInt(clean.substring(4,8));

               if(mon > 12) mon = 12;
               cal.set(Calendar.MONTH, mon-1);
               year = (year<1900)?1900:(year>2100)?2100:year;
               cal.set(Calendar.YEAR, year); 
               // ^ first set year for the line below to work correctly
               //with leap years - otherwise, date e.g. 29/02/2012
               //would be automatically corrected to 28/02/2012 

               day = (day > cal.getActualMaximum(Calendar.DATE))? cal.getActualMaximum(Calendar.DATE):day;
               clean = String.format("%02d%02d%02d",day, mon, year);
            }

            clean = String.format("%s/%s/%s", clean.substring(0, 2),
                clean.substring(2, 4),
                clean.substring(4, 8));

            sel = sel < 0 ? 0 : sel;
            current = clean;
            date.setText(current);
            date.setSelection(sel < current.length() ? sel : current.length());
        }
    }
We also implement the other two functions because we have to

    @Override
    public void beforeTextChanged(CharSequence s, int start, int count, int after) {}

    @Override
    public void afterTextChanged(Editable s) {}
};

TDD Academy is building a SSN TextWatcher which uses the same approach, but they are doing it by adding unit tests. @premspal @hemapanjakshram we'll defiantly fix that bug.
https://www.twitch.tv/tddacademy
https://m.youtube.com/channel/UCU1U6oPscxzKd_IWAIOm60w

The repo is at: https://github.com/lancerkind/Android-TDD-SSNTextBox/tree/usingOnTextChanged

Regardless of the bug, the above code is pretty close. Thanks for sharing!