I saw that he was flying a kite in the park just now.改为同义句

I saw him flying a kite in the park just now.
我看到他刚刚正在公园里放风筝
see sb. do sth. 和see sb. doing sth.
前者用于非持续性动词和持续性动词均可,表示看到某人做1件事情的全过程.
如 I saw you enter the door. （enter是非持续性动词,即1瞬间完成的动作）
I saw you play the game. (play是持续性动词,这里表示我看到你玩这个游戏的全过程)
后者只用语持续性动词,表示看到某人正在干着某事.
如 I saw you playing the game. (我看到你当时正在玩游戏.“玩游戏”显然是个可持续的过程.)
而不能说I saw you entering the door. (走进那个门是即时完成的,无法持续,无非是1脚跨进1脚跟上这么1瞬间.所以该句错)