#uiactivityviewcontroller

UIActivityViewController 기초설명

Last week I was working on a feature for a new app which involves sharing some data between two devices (encoded in a URL to link into the app on the receiver’s device) — with the catch being that the transfer has to happen over AirDrop (trust me, there’s a good reason for it). I eventually got an AirDrop-only share sheet working, but I thought it’d be fun (and hopefully interesting) to dig into the process I went through in figuring it out.

Now since Apple doesn’t provide a way to access AirDrop directly, I had to go through UIActivityViewController. My first thought was to use its excludedActivityTypes property and just load up an array with every activity type listed in UIActivity.h (other than AirDrop). That works great… except when you come to iOS 8’s third-party app extensions.

My next idea was to just put together a list of some of the more popular share extension identifiers and add those to the excludedActivityTypes array. This wouldn’t have been a great solution, as there would always be extensions slipping through (and it wouldn’t have worked at all, as it turns out). Though this line of thought did lead me to what I thought was a very clever idea…

I suspected (and a quick trip to the debugger verified that I was right) that UIActivityViewController was just checking each extension identifier against the excludedActivityTypes array — so what if I passed its setter a trick NSArray subclass which would have a containsObject: method that returned NO to any object other than UIActivityTypeAirDrop? This worked like a charm for hiding all of the system-provided sharing options, but despite the fact that the array was checked for each third-party share extension’s identifier, the results of that check were ignored. I was disappointed that I’d have to scrap what I thought was a clever and elegant solution.

Okay, so it was time to go deeper. I took a look at some iOS 8 runtime headers, subclassed UIActivityViewController, and started to play around with some private instance variables in the debugger… and _activityGroupListViewController proved to be the winner.

Its two arrays, _activityGroupViewControllers and _visibleActivityGroupViewControllers, when run on an AirDrop-capable device, contained an object of an interesting sounding class: SFAirDropActivityViewController. By removing any other view controllers from those arrays (and hiding their views) I was left with an AirDrop-exclusive share sheet. All that was left to do was alter that UIActivityGroupListViewController’s preferredContentSize and disable scrolling on its collection view and — ✨ta-da! ✨— a pretty straightforward way to AirDrop something.

This article will guide you about how to add a sharing option to your application.

For example the code below will share an integer value which is included in an NSString.  Furthermore it´s important that you can share multiple objects through the array. 

Sample Code:

Given the ever-burgeoning iOS app ecosystem, it makes sense to provide some sort of data interactivity with other applications in your own app, for the users' benefit.