Looking for a clear answer on how to reliably maintain a list of contacts in my application

I've been reading for a couple hours now, trying to figure out how to maintain a reliable list of contacts in an Android application, but still cannot find one clear successful case.

My situation is this: I let users create Groups in my application, and in each Group, the user can select, from their contact list on the phone, which users they'd like to add to that group. I then need to be able to have a reliable way to compare a call from an incoming contact with my contacts database in my application, to see if they are in specific groups.

The easy parts are to add specific contacts to my database, and also to look up a contact based on their phone number. Thanks to this forum they are easy anyway! :) I'm storing the contacts in my database by Contact Name, Lookup Key, and Contact Id. The hard part for me, and this is what I cannot find a clear answer on, is how do I know that a month down the road, Contact X is going to have the same Lookup Key or Contact Id as when they were added? Couldn't they all change by then? Obviously the name can easily change, but can't the lookup_key and Contact ID also change? I've read about the lookup_key changing 开发者_JAVA百科if contacts are manually aggregated. In other words, I am looking for the identifiable information for a contact that CANNOT change once they are entered?

I have read about using a ContentObserver to register for changes to the Contacts database, but I don't see that this helps me at all, since if I have Contact X with Lookup Key Y and Contact ID of Z, even if I get updated that the Contacts have changed, I still need to match Contact X in my application with Contact X in the Contacts database to update my info, which I still cannot do if the identifying information has been changed.

For example, I have a contact with Name, Lookup_Key, ContactID of Ted, 230ff392, 3209482. A month later, could it happen that what used to be Ted is now T-bone, 458ee247, 5502981? If this were the case, I cannot use these 3 identifiers as a means to look up the contact.

Thanks so much for the help on this! Paul

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I don't know where you read that the lookup key might change, but the documentation states that they are permanent in contrary to contact ids.

Contacts Provider / Contacts:

The ContactsContract.Contacts table also has the column LOOKUP_KEY that is a "permanent" link to the contact row. Because the Contacts Provider maintains contacts automatically, it may change a contact row's _ID value in response to an aggregation or sync. Even If this happens, the content URI CONTENT_LOOKUP_URI combined with contact's LOOKUP_KEY will still point to the contact row, so you can use LOOKUP_KEY to maintain links to "favorite" contacts, and so forth. This column has its own format that is unrelated to the format of the _ID column.