One of the features that will land as part of iOS 9 is a new way to display web content within an app by way of a new view controller called
SFSafariViewController, which is nicely covered by Federico Viticci in this article on MacStories. I’ve always been of the (apparently minority) opinion that iOS apps ought to open links in the default browser (which currently is necessarily Mobile Safari), but the Safari view controller might change my mind, because it pretty much removes any drawback the in-app UI/WKWebView-based browsers had: with the Safari view controller I will get a familiar and consistent interface (minus the editable address bar, of course), the same cookies as when I usually browse, my visits will be registered in the history, plus added security (and performance, though WKWebView already had that), etc. Come November, maybe I will stop long-tapping any and all links in my Twitter feed (in Twiterrific, of course) in order to bring the share sheet and open these links in Safari.
Part of my reluctance to use the in-app browsers was that I considered myself grown up enough to switch apps, then switch back to Twitter/Tumblr/whatever when I was done with reading the page: I have never considered app switching to be an inconvenience in the post-iOS 4 world, especially with the iOS 7+ multitasking interface. But I understand the motivation behind wanting to make sure the user goes back to whatever he was doing in the app once he is done reading the web content; and no, it is not about the app developers making sure the user does not stray far from the app (okay, it is not just about that): the user himself may fail to remember that he actually was engaged in a non-web-browsing activity and thus is better served, in my opinion, by a Safari experience contained in-app than he is by having to switch to Safari. For instance, if he is reading a book he would appreciate resuming reading the book as soon as he is done reading the web page given as reference, rather than risk forgetting he was reading a book in the first place and realize it the following day as he reopens the book app (after all, there is no reason why only John Siracusa ebooks should have web links).
And most interestingly, in order to deliver on all these features, the Safari view controller will run in its own process (even if, for app switching purposes for instance, it will still belong to the host app); this is a completely bespoke tech, to the best of my knowledge there is no framework on iOS for executing part of an app in a specific process as part of a different host app (notwithstanding app extensions, which provide a specific service to the host app, rather than the ability to run a part of the containing app). And this reminded me of Android activities.
For those of you not familiar with the Android app architecture, Android applications are organized around activities, each activity representing a level of full-screen interaction, e.g. the screen displaying the scrollable list of tweets complete with navigation bars at the top and/or bottom, with the activity changing when drilling down/back up the app interface, e.g. when tapping a tweet the timeline activity slides out and the tweet details activity slides in its place, with activities organized in a hierarchy. Android activities are roughly equivalent to view controllers on iOS, with a fundamental difference: installed apps can “vend” activities, that other apps can use as part of their activity hierarchy. For instance, a video player app can start with an activity listing the files found in its dedicated folder, then once such a file is tapped it starts the activity to play a single video, all the while also allowing any app, such as an email client or the file browser, that wants to play a video the ability to directly invoke the video-playing activity from within the host app.
I’ve always had reservations with this system: I thought it introduced user confusion as to which app the user “really” is in, which matters for app switching and app state management purposes, for instance. And I still do think so to an extent, but it is clear the approach has a lot of merit when it comes to the browser, given how pervasive visiting web links is even as part of otherwise very app-centric interactions. And maybe it could be worth generalizing and creating on iOS an activity-like system; sure, the web browser is pretty much the killer feature for such a system (I am more guarded about the merits when applying it to file viewing/editing, as in my video player example), but other reasonable applications could be considered.
So I’m asking you, would you like, as a user, to have activity-like features on iOS? Would you like, as a developer, to be able to provide some of your app’s view controllers to other apps, and/or to be able to invoke view controllers from other apps as part of your app?