Masked Input Using EditText Widget in Android

Try using an InputFilter rather than an OnKeyListener. This means you don't have worry about tracking individual key presses and it will also handle things like pasting into a field which would be painful to handle with an OnKeyListener.

You could have a look at the source of the InputFilter implementations that come with Android to give you a starting point for writing your own.

The easiest way I know to use a mask on EditText in your Android programs in Android Studio is to use MaskedEditText library (GitHub link). It's a kind of custom EditText with Watcher that allows you to set a hint with different color (if you want it will be available even when user already started to type), mask and it's very easy to use :-)

compile 'ru.egslava:MaskedEditText:1.0.5'

<br.com.sapereaude.maskedEditText.MaskedEditText
    android:id="@+id/phone_input"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:inputType="phone"
    android:typeface="monospace"
    mask:allowed_chars="1234567"
    mask:mask="###-##-##"
    app:keep_hint="true"
    />

And that is!