Reaml迁移

Question

public class Migration implements RealmMigration {

    @Override
    public void migrate(final DynamicRealm realm, long oldVersion, long newVersion) {
        RealmSchema schema = realm.getSchema();
        // Migrate from version 0 to version 1
        if (oldVersion == 0) {
            // Create a new class
            schema.create("DisabledGroup")
                    .addField("groupId", String.class, FieldAttribute.REQUIRED)
                    .addField("isMsgBlocked", Boolean.class, FieldAttribute.REQUIRED);
            oldVersion++;
        }
    }
}

io.realm.exceptions.RealmMigrationNeededException: Primary key not defined for field 'groupId' in existing Realm file. Add @PrimaryKey.