Mask an EditText with Phone Number Format NaN like in PhoneNumberUtils

Above answer is right but it works with country specific. if anyone want such formatted phone number(###-###-####). Then use this:

etPhoneNumber.addTextChangedListener(new TextWatcher() {
                @Override
                public void beforeTextChanged(CharSequence s, int start, int count, int after) {
                    int digits = etPhoneNumber.getText().toString().length();
                    if (digits > 1)
                        lastChar = etPhoneNumber.getText().toString().substring(digits-1);
                }

                @Override
                public void onTextChanged(CharSequence s, int start, int before, int count) {
                    int digits = etPhoneNumber.getText().toString().length();
                    Log.d("LENGTH",""+digits);
                    if (!lastChar.equals("-")) {
                        if (digits == 3 || digits == 7) {
                            etPhoneNumber.append("-");
                        }
                    }
                }

                @Override
                public void afterTextChanged(Editable s) {

                }
            });

Declare String lastChar = " " in your activity.

Now add this line in xml of your edittext

android:inputType="phone"

That's all.

Edited: If you want your edittext lenght to limit 10 digits add line below also:

android:maxLength="12"

(It is 12 because "-" will take space two times)

Easiest way to do this is to use the built in Android PhoneNumberFormattingTextWatcher.

So basically you get your EditText in code and set your text watcher like this...

EditText inputField = (EditText) findViewById(R.id.inputfield);
inputField.addTextChangedListener(new PhoneNumberFormattingTextWatcher());

Nice thing about using PhoneNumberFormattingTextWatcher is that it will format your number entry correctly based on your locale.

Just add the following to EditText for Phone Number to get a formatted phone number(###-###-####)

Phone.addTextChangedListener(new TextWatcher() {

        int length_before = 0;

        @Override
        public void beforeTextChanged(CharSequence s, int start, int count, int after) {
            length_before = s.length();
        }

        @Override
        public void onTextChanged(CharSequence s, int start, int before, int count) {

        }

        @Override
        public void afterTextChanged(Editable s) {
            if (length_before < s.length()) {
                if (s.length() == 3 || s.length() == 7)
                    s.append("-");
                if (s.length() > 3) {
                    if (Character.isDigit(s.charAt(3)))
                        s.insert(3, "-");
                }
                if (s.length() > 7) {
                    if (Character.isDigit(s.charAt(7)))
                        s.insert(7, "-");
                }
            }
        }
    });