无法在UIScrollView中点击UIButton

Question

我创建了一个具有以下结构的视图：

UIView (super view, freeform- width: 320, height: 1800)

.UIScrollView ( constraint: top, bottom, leading, trailing =0 )

..ContentView ( constraint: top, bottom, leading, trailing with UIScollView = 0, constraint height, width are equal to UIVIew's height, width )

...UIButton ( some red button near top of ContentView, some blue near bottom of it )

结果：我可以点按红色按钮，但不能点按蓝色按钮。 我猜蓝色按钮不在内容视图中。

你知道我的问题和任何解决方案吗？