Question

I’m working on developing an app for Android and need to store contact ID’s in order to keep track of a subset of contacts for use in the app. I’m currently storing the ID’s in a table that’s used locally, but this table becomes inconsistent if a contact is merged with other contacts (the ID used to represent the merged contact often changes). What is the best way to maintain consistency?

My ideas:

• If there were some sort of intent or system event that is broadcasted then I could listen for that.

• If the mapping between old ID’s and new ID’s is kept somewhere (ContactsContract.RawContacts?) then I could refresh the field whenever I detect that an ID is no longer valid.

• Run a background process with a content observer and watch for changes. I’d like to avoid this if possible.

This question seems to tackle a similar problem, but for adding instead of merging contacts: Reacting to new contacts in Android Contacts application.

Any and all ideas welcome!

Answer 1

Store the contact lookup URI (as a string). This URI is created from the _id along with the contact lookup_key. These two can build a lookup URI by calling ContactsContract.getLookupUri(). You can lookup the contact by calling ContactsContract.lookupContact() and querying CONTENT_URI or by querying CONTENT_LOOKUP_URI with the lookup URI directly. The Android docs say this about the 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.