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I have an app that gets the ContactsContract.Contacts.LOOKUP_KEY of a contact on the device and saves it on the app Db.

After reading this page I thought I could use the LOOKUP_KEY to uniquely identify a contact, even when a contact is edited (for example after editing the name of the contact).

Actually I saw that after editing a contact, its LOOKUP_KEY changes, so I cannot use anymore the LOOKUP_KEY I saved on my app DB.

My question is: is there a way to uniquely identify a contact on ContactsContract.Contacts from when it is created for the first time on the device until it is deleted from the device?

Thank you

MDP
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2 Answers2

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A LOOKUP_KEY is not meant to be used as a key on its own, instead it should be used together with a contact's _ID to form a full lookupUri.

The lookupUri can then be used to find a contact in CONTENT_LOOKUP_URI tables. The CONTENT_LOOKUP_URI basically first looks for the contact by _ID, if it fails to find it, or the _ID seems like the wrong contact, it uses hints from the LOOKUP_KEY part to try and track down the correct contact for you.

From CONTENT_LOOKUP_URI

A content:// style URI for this table that should be used to create shortcuts or otherwise create long-term links to contacts. This URI should always be followed by a "/" and the contact's LOOKUP_KEY. It can optionally also have a "/" and last known contact ID appended after that. This "complete" format is an important optimization and is highly recommended.

As long as the contact's row ID remains the same, this URI is equivalent to CONTENT_URI. If the contact's row ID changes as a result of a sync or aggregation, this URI will look up the contact using indirect information (sync IDs or constituent raw contacts).

Lookup key should be appended unencoded - it is stored in the encoded form, ready for use in a URI.

From getLookupUri(long contactId, String lookupKey)

Build a CONTENT_LOOKUP_URI lookup Uri using the given _ID and LOOKUP_KEY.

From LOOKUP_KEY

An opaque value that contains hints on how to find the contact if its row id changed as a result of a sync or aggregation.

marmor
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  • So the best way to identify a contact is by what you get from `getLookupUri`? and not "lookupKey" that is passed to it, right, as the question says? Supposed I wish to have a DB that has extra information about each contact, should I have the "lookupUri", or actually the "lookupKey"&"contactId" (that together I can make the "lookupUri" from them ? And how does it know when "the _ID seems like the wrong contact" ? – android developer Aug 04 '19 at 13:57
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The row id (primary key) for each contact called _ID.

Yossi Segev
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