Better way to get contact details via content provider in Android

Generally, to get the mobile numbers, name and email address, you need to make a different query to a content resolver in Android. You get data from different queries; merge all those together to put the data in a single collection and show it on UI.

Multiple queries are performance hit as DB query involves connect, query and disconnect so fewer the queries, better the performance.

Old Approach :

1. Get the list of contacts to contactCursor from Contacts.CONTENT_URI
2. Get all phone numbers to phoneCursor from Phone.CONTENT_ITEM_TYPE
3. Get all emails to emailCursor from Email.CONTENT_ITEM_TYPE
4. Link: https://gist.github.com/srayhunter/47ab2816b01f0b00b79150150feb2eb2

New, Better and Optimized Approach :

I used the Rx Java approach to fetch the contact details on the separate observable.

Declare variables and constants

private const val DISPLAY_NAME = ContactsContract.Contacts.DISPLAY_NAME_PRIMARY
private val PROJECTION = arrayOf(
    ContactsContract.Data.CONTACT_ID,
    ContactsContract.Contacts.HAS_PHONE_NUMBER,
    ContactsContract.Data.DISPLAY_NAME,
    ContactsContract.Data.DATA1,
    ContactsContract.Data.MIMETYPE
)
private const val ORDER = DISPLAY_NAME
private const val selection = ContactsContract.Data.MIMETYPE + " = ?" +
        " OR " + ContactsContract.Data.MIMETYPE + " = ?" + " OR " + ContactsContract.Data.MIMETYPE + " = ?"
private val selectionArgs = arrayOf(
    "%" + "@" + "%",
    ContactsContract.CommonDataKinds.Email.CONTENT_ITEM_TYPE,
    ContactsContract.CommonDataKinds.Phone.CONTENT_ITEM_TYPE
)

and call the below code on separate observable or on a separate thread

val userContactDetailLinkedHashMap: LinkedHashMap<Int, UserContactDetail?> = LinkedHashMap()
try {
    val cr: ContentResolver = context.getContentResolver()
    val cur: Cursor = cr.query(
        ContactsContract.Data.CONTENT_URI,
        PROJECTION,
        selection,
        selectionArgs,
        ORDER
    )
    if (cur != null && cur.getCount()>0 && cur.moveToFirst()) {
        do {
            val hasPhone: Int =
                cur.getInt(cur.getColumnIndex(ContactsContract.Contacts.HAS_PHONE_NUMBER))
            val contactId: Int =
                cur.getInt(cur.getColumnIndex(ContactsContract.Data.CONTACT_ID))
            val name: String =
                cur.getString(cur.getColumnIndex(ContactsContract.Data.DISPLAY_NAME_PRIMARY))
            val emailOrMobile: String? =
                cur.getString(cur.getColumnIndex(ContactsContract.Data.DATA1))
            if (hasPhone > 0 && emailOrMobile != null) {
                var contactDetail: UserContactDetail?
                if (!userContactDetailLinkedHashMap.containsKey(contactId)) {
                    contactDetail = UserContactDetail()
                    if (!CommonUtil.isEmailValid(emailOrMobile)) {
                        contactDetail.setPhoneNumber(Collections.singletonList(emailOrMobile))
                    } else {
                        contactDetail.setEmailId(Collections.singletonList(emailOrMobile))
                    }
                    contactDetail.setName(name)
                    userContactDetailLinkedHashMap[contactId] = contactDetail
                } else {
                    contactDetail = userContactDetailLinkedHashMap[contactId]
                    if (contactDetail == null) continue
                    if (!CommonUtil.isEmailValid(emailOrMobile)) {
                        contactDetail.setPhoneNumber(Collections.singletonList(emailOrMobile))
                    } else {
                        contactDetail.setEmailId(Collections.singletonList(emailOrMobile))
                    }
                    contactDetail.setName(name)
                    userContactDetailLinkedHashMap[contactId] = contactDetail
                }
            }
        } while (cur.moveToNext())
    }
    if (cur != null) {
        cur.close()
    }
} catch (e: Exception) {
    Crashlytics.getInstance().core.logException(e)
}

Here the UserContactDetail have

class UserContactDetail {
    var name: String? = null
    var emailId: List<String> = ArrayList()
    var phoneNumber: List<String> = ArrayList()
}

That's it. LinkedHashMap userContactDetailLinkedHashMap will have the final user details along with name, emails and mobile numbers.