据this SO项，在ActionBar仅当可用宽度小于480dp分裂。据谷歌的戴安娜Hackborn这篇文章然而，Nexus 7保护的纵向宽度为600dp 。所以这就是原因没有分裂。

According to this SO item, the ActionBar is only splitted when the available width is less than 480dp. According to this article of Google's Dianne Hackborn however, the portrait width of the Nexus 7 is 600dp. So that's the reason there's no splitting.

我同意你的看法，即分裂应取决于可用空间和项目之间的关系表现出来，而不是单独的可用空间。

I agree with you, that the splitting should depend on the relation between available space and items to be shown, not on the available space alone.