How to read contacts in Android using Realm?

Create RealmObject, read the data from content provider, save data to RealmObject, save data in Realm:

// background thread
Realm realm = null;
try {
    realm = Realm.getDefaultInstance();
    realm.executeTransaction(new Realm.Transaction() {
        @Override
        public void execute(Realm realm) {
            RealmContact realmContact = new RealmContact();
            Cursor phones = getContentResolver().query(ContactsContract.CommonDataKinds.Phone.CONTENT_URI, null, null, null, null);
            while (phones.moveToNext()) {
               String name = phones.getString(phones.getColumnIndex(ContactsContract.CommonDataKinds.Phone.DISPLAY_NAME));
               String phoneNumber = phones.getString(phones.getColumnIndex(ContactsContract.CommonDataKinds.Phone.NUMBER));
               realmContact.setName(name);
               realmContact.setPhoneNumber(phoneNumber);
               realm.insertOrUpdate(realmContact);
            }
        }
    });
} finally {
    if(realm != null) {
        realm.close();
    }
}

EDIT: okay, here’s a trick to merging data and removing all data that’s not in the list you’ve saving

public class RealmContract extends RealmObject {
    @PrimaryKey
    private long id;

    @Index
    private String name;

    @Index
    private String phoneNumber;

    @Index
    private boolean isBeingSaved;

    //getters, setters
}

Then merge:

// background thread
Realm realm = null;
try {
    realm = Realm.getDefaultInstance();
    realm.executeTransaction(new Realm.Transaction() {
        @Override
        public void execute(Realm realm) {
            RealmContact realmContact = new RealmContact();
            Cursor phones = getContentResolver().query(ContactsContract.CommonDataKinds.Phone.CONTENT_URI, null, null, null, null);
            while (phones.moveToNext()) {
               String id = phones.getString(phones.getColumnIndex(ContactsContract.CommonDataKinds._ID));
               String name = phones.getString(phones.getColumnIndex(ContactsContract.CommonDataKinds.Phone.DISPLAY_NAME));
               String phoneNumber = phones.getString(phones.getColumnIndex(ContactsContract.CommonDataKinds.Phone.NUMBER));
               realmContact.setId(id);
               realmContact.setName(name);
               realmContact.setPhoneNumber(phoneNumber);
               realmContact.setIsBeingSaved(true);
               realm.insertOrUpdate(realmContact);
            }
            realm.where(RealmContact.class)
                 .equalTo(RealmContactFields.IS_BEING_SAVED, false) // compile 'dk.ilios:realmfieldnameshelper:1.0.0'
                 .findAll()
                 .deleteAllFromRealm(); // delete all non-saved data
            for(RealmContact realmContact : realm.where(RealmContact.class).findAll()) { // realm 0.89.0+
                realmContact.setIsBeingSaved(false); // reset all save state
            }
        }
    });
} finally {
    if(realm != null) {
        realm.close();
    }
}

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EDIT: Refer to OP’s other question for reading contact data reliably (because there’s something up with the Contact LOOKUP_ID and making sure the IDs are correct): Obtaining contacts from content provider without duplicates or invalid contacts, and save to Realm