EditText for typing a license

Question

On my android app, first time when app runs, user must type a license. The license's format is ###-XXX-###-### where # is a number, X is a character. I put the format as hint but it is not sufficient. How can I make like this and user does not enter -, it just appear after 3 characters ?

UPDATE :

That's my code and it works :

licenseEditText.addTextChangedListener(new TextWatcher() {

            public void afterTextChanged(Editable s) {
                System.out.println("afterTextChanged");
                if (s.length() == 3) {
                    s.append("-");
                }
                if (s.length() == 7) {
                    s.append("-");
                }
                if (s.length() == 11) {
                    s.append("-");
                }
                if (s.length() == 15)
                    ok.performClick();
            }

            public void beforeTextChanged(CharSequence s, int start, int count,
                    int after) {
                System.out.println("beforeTextChanged");
            }

            public void onTextChanged(CharSequence s, int start, int before,
                    int count) {
                System.out.println("onTextChanges");

            }
        });

Answer 1

set a TextWatcher , inside it compare intered text with a regularExpression . and put other code like after first 3 charachets append "-" to intered characterSet .