Example for reading contacts in Android

Contact

data class Contact(val id: String = "", val name: String = "", val photoUri: String = "", var phoneNumber: String = "", val typeStringRes: Int = 0)

Contact repository

class ContactRepository {

    companion object {
        private val CONTACTS_PROJECTION = arrayOf(Contacts._ID,
                Contacts.DISPLAY_NAME_PRIMARY,
                Contacts.PHOTO_THUMBNAIL_URI,
                Contacts.HAS_PHONE_NUMBER)

        private val DATA_PROJECTION = arrayOf(ContactsContract.Data.CONTACT_ID,
                ContactsContract.Data.DATA1,
                ContactsContract.Data.MIMETYPE,
                CommonDataKinds.Phone.TYPE)
    }

    fun getContacts(resolver: ContentResolver): Observable<Contact> {
        return Observable.fromEmitter<Contact>({ emitter ->
            val contactsCursor = getContactsCursor(resolver)
            val phonesCursor = getPhonesCursor(resolver)
            fetchContactsFromCursor(contactsCursor, phonesCursor, emitter)
            emitter.onCompleted()
        }, BackpressureMode.BUFFER)
    }

    private fun getContactsCursor(resolver: ContentResolver): Cursor? {
        return resolver.query(
                Contacts.CONTENT_URI,
                CONTACTS_PROJECTION,
                "${Contacts.HAS_PHONE_NUMBER} >0",
                null,
                "${Contacts._ID} ASC")
    }

    private fun getPhonesCursor(resolver: ContentResolver): Cursor? {
        val args = arrayOf(CommonDataKinds.Phone.CONTENT_ITEM_TYPE)

        val data = resolver.query(
                ContactsContract.Data.CONTENT_URI,
                DATA_PROJECTION,
                "${ContactsContract.Data.MIMETYPE}=?",
                args,
                "${ContactsContract.Data.CONTACT_ID} ASC")

        return data
    }

    fun getContactById(resolver: ContentResolver, id: String): Observable<Contact> {
        return Observable.fromEmitter({ emitter ->
            val contactCursor = getContactCursor(id, resolver)
            val phonesCursor = getContactPhonesCursor(id, resolver)
            fetchContactsFromCursor(contactCursor, phonesCursor, emitter)
            emitter.onCompleted()
        }, BackpressureMode.BUFFER)
    }


    private fun getContactCursor(id: String, resolver: ContentResolver): Cursor? {
        val args = arrayOf(id)
        return resolver.query(
                Contacts.CONTENT_URI,
                CONTACTS_PROJECTION,
                "${Contacts.HAS_PHONE_NUMBER} >0 AND ${Contacts._ID} =?",
                args,
                null)
    }

    private fun getContactPhonesCursor(id: String?, resolver: ContentResolver): Cursor? {
        val args = arrayOf(id, CommonDataKinds.Phone.CONTENT_ITEM_TYPE)

        val data = resolver.query(
                ContactsContract.Data.CONTENT_URI,
                DATA_PROJECTION,
                "${ContactsContract.Data.CONTACT_ID}=? AND ${ContactsContract.Data.MIMETYPE}=?",
                args,
                null)

        return data
    }


    private fun fetchContactsFromCursor(contactsCursor: Cursor?, phonesCursor: Cursor?, emitter: Emitter<Contact>) {
        try {
            if (contactsCursor != null && phonesCursor != null) {

                var id: String = ""
                var name: String = ""
                var photoUri: String = ""
                while (phonesCursor.moveToNext() && contactsCursor.isAfterLast.not()) {

                    val phoneNumber = phonesCursor.getStringByColumn(ContactsContract.Data.DATA1)
                    val type = phonesCursor.getIntByColumn(CommonDataKinds.Phone.TYPE)
                    val typeStringRes = CommonDataKinds.Phone.getTypeLabelResource(type)
                    val contactId = phonesCursor.getStringByColumn(ContactsContract.Data.CONTACT_ID)

                    if (id.equals(contactId).not()) {
                        contactsCursor.moveToNext()
                        id = contactsCursor.getStringByColumn(Contacts._ID) ?: ""
                        name = contactsCursor.getStringByColumn(Contacts.DISPLAY_NAME_PRIMARY) ?: ""
                        photoUri = contactsCursor.getStringByColumn(Contacts.PHOTO_THUMBNAIL_URI) ?: ""
                    }

                    if (phoneNumber.isNullOrEmpty().not()) {
                        val contact = Contact(id, name, photoUri, phoneNumber!!, typeStringRes)
                        emitter.onNext(contact)
                    }
                }
            }
        } finally {
            contactsCursor?.close()
            phonesCursor?.close()
        }
    }

    private fun Cursor.getStringByColumn(column: String): String? {
        try {
            return getString(getColumnIndex(column))
        } catch(e: Exception) {
            return null
        }
    }

    private fun Cursor.getIntByColumn(column: String): Int {
        try {

            return getInt(getColumnIndex(column))
        } catch(e: Exception) {
            return ResourcesUtil.ILLEGAL_RES
        }
    }
}