John Wesley on 1 Chronicles 29:22

The second time - The first time, was when he was made king during Adonijah's conspiracy. And Zadok - It must be remembered that the high - priest had his viceregent who might officiate in his stead. So that this action of theirs, the anointing Zadok, did not, actually constitute him high - priest, but only settled the reversion of it upon him and his line after Abiathar's death; even as David's making Solomon king, and their anointing Solomon to be the chief governor here, did not put him into actual possession of the kingdom, but only gave him a right to it after the present king's death: hence, notwithstanding this anointing, Abiathar continued to exercise his office 'till Solomon thrust him out, 1Kings 2:27.