This is the first chapter of a section explaining why Saul wants to kill David. Saul's son, Jonathan, loves David. David is successful in battling the Philistines, and Saul is happy until the women give David more attention than they give him. He fears that David will replace him as king. This is potentially confusing because the author has already established that David will be the next king. It is probably that Saul feared David would kill him in order to be the next king sooner, or that he did not really believe David would be the next king.
"Jonathan felt a strong affection towards David" or "Jonathan committed himself to David". Some scholars believe Jonathan loved David as a man loves his wife. There is no reason to translate this as if Jonathan were a homosexual. Instead, treat this as a brotherly type of love.