android - 向上操作后的返回键行为

Question

这里http://developer.android.com/design/patterns/navigation.html是一些关于后退和向上导航的提示。很清楚up在这个例子中做了什么，它关闭了这些活动。

但是这里发生了什么？我去市场，打开书，然后另一本书，然后打开电影，然后我决定按下去电影类别。
图书活动发生了什么？
我能以某种方式去找他们吗？
当我点击返回按钮时，我去哪里市场？

Answer 1

UP 按钮将在 App 内导航。UP 按钮确保用户留在 App 内。应用程序的最顶部屏幕不应显示 UP 按钮。

但是，系统 BACK 按钮可以将用户返回到主屏幕，甚至返回到不同的应用程序，这与 UP 按钮不同。当先前查看的屏幕也是当前屏幕的分层父级时，按 Back 按钮与按 Up 按钮的结果相同

Answer 2

I don't think there is book activities, I think it is fragments. But about your question. If you read the navigation details it states:

The system Back button is used to navigate, in reverse chronological order, through the history of screens the user has recently worked with. It is generally based on the temporal relationships between screens, rather than the app's hierarchy.

In other words you should go back to selected movie, from there the selected book and etc. This however needs to be implemented by the developer and often it isn't. Which is why back button might just bring you back to market/play store from the movies top category.

Edit: So above was my first thought. Based on experimenting with google apps and looking into the example I change my advice to following:

When you go up to the new root (movie) then the app should close. The reason for this is simply that the user has navigated to a new top hierachy and would probarbly be anoyed by having to go through whole the last navigation. This also means that when the user clicks up in movies whole the back track stack is lost.