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I have a problem with switching activities & fragments on certain device sizes, when an orientation change happens. In my case it's large screens, but it could happen with other screen sizes depending on the app. I've looked around for answers, but nothing seems to properly address this.

I have two activities, MainActivity and SubordinateActivity. MainActivity is the only entry point to the app; MainActivity launches SubordinateActivity. Each activity has its own fragment, MainFragment and SubordinateFragment. When running on normal devices, there is only enough space on the screen for one fragment at a time, regardless of the orientation. In that case, each activity will manage its own fragment. On xlarge devices, there is enough space for two fragments, regardless of the orientation. In this case, there are different layout files which allow for two fragments on the screen. Both MainFragment and SubordinateFragment are managed by MainActivity (SubordinateActivity is never used).

The trouble arises with large screens. Using landscape orientation, there's enough space for two fragments, but in portrait orientation there is not. I have the proper layout files for each. In landscape mode, MainActivity manages both fragments (as with xlarge devices) and in portrait mode, each activity manages its own fragment (as with normal devices). This produces problems in two scenarios:

  1. SubordinateActivity is loaded in portrait mode, and the orientation changes to landscape mode. What I want: SubordinateActivity should be discarded and MainActivity should load, with the content previously displayed by SubordinateActivity, displayed in its own SubordinateFragment. Problem: SubordinateActivity stays loaded by itself in landscape mode.
  2. MainActivity is loaded with MainFragment and SubordinateFragment in landscape mode, and the orientation switches to portrait. What I want: The content previously displayed in SubordinateFragment should now be displayed alone by SubordinateActivity. Problem: MainActivity is shown with only the content from MainFragment.

A good example of this problem is the GMail app. Here are some screen shots from that app in case it's not clear what I'm talking about. I realize the UI of the GMail app is actually more complicated than mine, but the problem is the same.

GMail message list GMail message display

GMail in landscape orientation on large device

I'm sure that this is a problem others have encountered because the GMail developers encountered it too. I can't figure out what a good solution is, because every possibility seems to involve either violating the Android UI best practices, or creating some ungodly tangle between Activity code and XML layouts.

Here are some ideas I have, none of which seems really correct:

  • Detect the orientation change in both activities, and launch the other activity (eg, by using FLAG_ACTIVITY_CLEAR_TOP) to go back down the stack and load a previously loaded activity, with a new intent. This is a problem because the orientation change code should only be executed on large devices, which means mingling code that checks which layouts are available with the activity code.
  • Drop SubordinateActivity altogether. It seems a bit superfluous and MainActivity can manage the fragments itself, even on normal size devices where it can just swap MainFragment and SubordinateFragment as necessary. In the end I don't think this solves the problem since MainActivity still relies on the layout files to tell it which and how many fragments to display. This also would violate the principle that an Activity represents a discrete thing that the user does.

Here are some resources I've been looking at to try to solve this problem. As I said, this seems to be a common problem, but there seems to be no canonical Android solution. This is a bit of a shortcoming since the documentation recommends using Fragments, and every developer who does, is going to run into this problem.

Summary: I have the multi-pane mode working for xlarge devices. The problem I'm trying to solve is switching between single pane (portrait) and multi-pane (landscape) mode on large devices that can only handle multiple panes in landscape orientation.

Community
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Paul Holden
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    OH! I'm on tears. One of the VERY FEW questions properly researched and properly written before being asked I've seen since a while. Good luck finding your solution! Unfortunately i cannot contribute except with a +1 and a star – STT LCU Aug 30 '13 at 14:55

1 Answers1

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Kill SubordinateActivity and have the only entry point in your application be MainActivity which then decides to either fill the entire viewport with MainFragment or SubordinateFragment. You can find an example on how to do this by looking at the developer docs for the design guide you linked to.

After you do this, you can create a resource folder specific for large and landscape, res/layout/large-land as stated here and set up your layout file for MainActivity to include two fragments similar to lesson #2 in the link from the previous paragraph.

Creating that, alongside your normal XML layouts changing to what's described in that doc should automatically handle everything you're describing since an orientation change is technically an activity re-creation.

Kasra Rahjerdi
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  • By "kill SubordinateActivity" do you mean remove it from the code, using only a single activity, as in my second option listed above, or something different? Also, to clarify, MainActivity is the only entry point. – Paul Holden Aug 31 '13 at 16:51
  • I mean only use a single activity. What you're doing is pretty close to a master-detail view which works best with one activity. – Kasra Rahjerdi Sep 01 '13 at 15:30