Java 1 2 3 4 5 6 7 8 9 10 11 12 // The Javascript interface object in Kotlin class WebkitJsInterface (context: Context) { private val mContext = context // ContactJsInterface.getContacts() maps to this method @JavascriptInterface fun getContacts () { mContext.contentResolver.query( ContactsContract.Contacts.CONTENT_URI, null , null , null , null ) } } For severe unexpected errors, it might not be bad to let the app crash, as you would, while writing the Java code.