By the time的用法书上打by the time we get there,it will be closed.

By the time的用法
书上打by the time we get there,it will be closed.
我想问为什麼不是by the time we get there,it will have been closed.
但他另一个例子by the time we get to the cinema,the film will already have started.就用了将来完成式?这是怎麼回事?
还是by the time 後面跟两种时式都可以吗?还是说怎麼分?