title

author

UIActivityCategoryAction

UIActivityTypePrint
UIActivityTypeCopyToPasteboard
UIActivityTypeAssignToContact
UIActivityTypeSaveToCameraRoll
UIActivityTypeAddToReadingList
UIActivityTypeAirDrop

UIActivityCategoryShare

UIActivityTypeMessage
UIActivityTypeMail
UIActivityTypePostToFacebook
UIActivityTypePostToTwitter
UIActivityTypePostToFlickr
UIActivityTypePostToVimeo
UIActivityTypePostToTencentWeibo
UIActivityTypePostToWeibo

Each activity type supports a number of different data types. For example, a Tweet might be composed of an NSString, along with an attached image and/or URL.

Supported Data Types by Activity Type

Activity Type	String	Attributed String	URL	Data	Image	Asset	Other
Post To Facebook	✓	✓	✓		✓
Post To Twitter	✓	✓	✓		✓
Post To Weibo	✓	✓	✓		✓	✓
Message	✓	✓	✓*	✓*		✓*	`sms://` `NSURL`
Mail	✓+	✓+	✓+
Print				✓+	✓+		`UIPrintPageRenderer`, `UIPrintFormatter`, & `UIPrintInfo`
Copy To Pasteboard	✓		✓		✓		`UIColor`, `NSDictionary`
Assign To Contact					✓
Save To Camera Roll			✓		✓
Add To Reading List			✓
Post To Flickr			✓	✓	✓	✓
Post To Vimeo			✓	✓		✓
Post To Tencent Weibo	✓	✓	✓		✓	✓
AirDrop	✓	✓	✓		✓	✓

`<UIActivityItemSource>` & `UIActivityItemProvider`

Similar to how a pasteboard item can be used to provide data only when necessary, in order to avoid excessive memory allocation or processing time, activity items can be of a custom type.

Any object conforming to <UIActivityItemSource>, including the built-in UIActivityItemProvider class, can be used to dynamically provide different kinds of data depending on the activity type.

`<UIActivityItemSource>`

Getting the Data Items

activityViewControllerPlaceholderItem:
activityViewController:itemForActivityType:

Providing Information About the Data Items

activityViewController:subjectForActivityType:
activityViewController:dataTypeIdentifierForActivityType:
activityViewController:thumbnailImageForActivityType:suggestedSize:

One example of how this could be used is to customize a message, depending on whether it's to be shared on Facebook or Twitter.

func activityViewController(activityViewController: UIActivityViewController, itemForActivityType activityType: String) -> AnyObject? {
    if activityType == UIActivityTypePostToFacebook {
        return NSLocalizedString("Like this!", comment: "comment")
    } else if activityType == UIActivityTypePostToTwitter {
        return NSLocalizedString("Retweet this!", comment: "comment")
    } else {
        return nil
    }
}

- (id)activityViewController:(UIActivityViewController *)activityViewController
         itemForActivityType:(NSString *)activityType
{
    if ([activityType isEqualToString:UIActivityTypePostToFacebook]) {
        return NSLocalizedString(@"Like this!");
    } else if ([activityType isEqualToString:UIActivityTypePostToTwitter]) {
        return NSLocalizedString(@"Retweet this!");
    } else {
        return nil;
    }
}

Creating a Custom UIActivity

In addition to the aforementioned system-provided activities, its possible to create your own activity.

As an example, let's create a custom activity type that takes an image URL and applies a mustache to it using mustache.me.


Before	After

First, we define a reverse-DNS identifier for the activity type:

let HIPMustachifyActivityType = "com.nshipster.activity.Mustachify"

static NSString * const HIPMustachifyActivityType = @"com.nshipster.activity.Mustachify";

Then specify the category as UIActivityCategoryAction and provide a localized title & iOS version appropriate image:

// MARK: - UIActivity

override class func activityCategory() -> UIActivityCategory {
    return .Action
}

override func activityType() -> String? {
    return HIPMustachifyActivityType
}

override func activityTitle() -> String? {
    return NSLocalizedString("Mustachify", comment: "comment")
}

override func activityImage() -> UIImage? {
    if #available(iOS 7.0, *) {
        return UIImage(named: "MustachifyUIActivity7")
    } else {
        return UIImage(named: "MustachifyUIActivity")
    }
}

#pragma mark - UIActivity

+ (UIActivityCategory)activityCategory {
    return UIActivityCategoryAction;
}

- (NSString *)activityType {
    return HIPMustachifyActivityType;
}

- (NSString *)activityTitle {
    return NSLocalizedString(@"Mustachify", nil);
}

- (UIImage *)activityImage {
    if (NSFoundationVersionNumber > NSFoundationVersionNumber_iOS_6_1) {
        return [UIImage imageNamed:@"MustachifyUIActivity7"];
    } else {
        return [UIImage imageNamed:@"MustachifyUIActivity"];
    }
}

Next, we create a helper function, HIPMatchingURLsInActivityItems, which returns an array of any image URLs of the supported type.

func HIPMatchingURLsInActivityItems(activityItems: [AnyObject]) -> [AnyObject] {
    return activityItems.filter {
        if let url = $0 as? NSURL where !url.fileURL {
            return url.pathExtension?.caseInsensitiveCompare("jpg") == .OrderedSame
                || url.pathExtension?.caseInsensitiveCompare("png") == .OrderedSame
        }

        return false
    }
}

static NSArray * HIPMatchingURLsInActivityItems(NSArray *activityItems) {
    return [activityItems filteredArrayUsingPredicate:[NSPredicate predicateWithBlock:
    ^BOOL(id item, __unused NSDictionary *bindings) {
        if ([item isKindOfClass:[NSURL class]] &&
            ![(NSURL *)item isFileURL]) {
            return [[(NSURL *)item pathExtension] caseInsensitiveCompare:@"jpg"] == NSOrderedSame ||
            [[(NSURL *)item pathExtension] caseInsensitiveCompare:@"png"] == NSOrderedSame;
        }

        return NO;
    }]];
}

This function is then used in -canPerformWithActivityItems: and prepareWithActivityItems: to get the mustachio'd image URL of the first PNG or JPEG, if any.

override func canPerformWithActivityItems(activityItems: [AnyObject]) -> Bool {
    return HIPMatchingURLsInActivityItems(activityItems).count > 0
}

override func prepareWithActivityItems(activityItems: [AnyObject]) {
    let HIPMustachifyMeURLFormatString = "http://mustachify.me/%d?src=%@"

    if let firstMatch = HIPMatchingURLsInActivityItems(activityItems).first, mustacheType = self.mustacheType {
        imageURL = NSURL(string: String(format: HIPMustachifyMeURLFormatString, [mustacheType, firstMatch]))
    }

    // ...
}

- (BOOL)canPerformWithActivityItems:(NSArray *)activityItems {
    return [HIPMatchingURLsInActivityItems(activityItems) count] > 0;
}

- (void)prepareWithActivityItems:(NSArray *)activityItems {
    static NSString * const HIPMustachifyMeURLFormatString = @"http://mustachify.me/%d?src=%@";

    self.imageURL = [NSURL URLWithString:[NSString stringWithFormat:HIPMustachifyMeURLFormatString, self.mustacheType, [HIPMatchingURLsInActivityItems(activityItems) firstObject]]];
}

Our webservice provides a variety of mustache options, which are defined in an enumeration:

enum HIPMustacheType: Int {
    case English, Horseshoe, Imperial, Chevron, Natural, Handlebar
}

typedef NS_ENUM(NSInteger, HIPMustacheType) {
    HIPMustacheTypeEnglish,
    HIPMustacheTypeHorseshoe,
    HIPMustacheTypeImperial,
    HIPMustacheTypeChevron,
    HIPMustacheTypeNatural,
    HIPMustacheTypeHandlebar,
};

Finally, we provide a UIViewController to display the image. For this example, a simple UIWebView controller suffices.

class HIPMustachifyWebViewController: UIViewController, UIWebViewDelegate {
    var webView: UIWebView { get }
}

@interface HIPMustachifyWebViewController : UIViewController <UIWebViewDelegate>
@property (readonly, nonatomic, strong) UIWebView *webView;
@end

func activityViewController() -> UIViewController {
    let webViewController = HIPMustachifyWebViewController()

    let request = NSURLRequest(URL: imageURL)
    webViewController.webView.loadRequest(request)

    return webViewController
}

- (UIViewController *)activityViewController {
    HIPMustachifyWebViewController *webViewController = [[HIPMustachifyWebViewController alloc] init];

    NSURLRequest *request = [NSURLRequest requestWithURL:self.imageURL];
    [webViewController.webView loadRequest:request];

    return webViewController;
}

To use our brand new mustache activity, we simply pass it in the UIActivityViewController initializer:

let mustacheActivity = HIPMustachifyActivity()
let activityViewController = UIActivityViewController(activityItems: [imageURL], applicationActivities: [mustacheActivity])

HIPMustachifyActivity *mustacheActivity = [[HIPMustachifyActivity alloc] init];
UIActivityViewController *activityViewController =
  [[UIActivityViewController alloc] initWithActivityItems:@[imageURL]
                                    applicationActivities:@[mustacheActivity]];

Invoking Actions Manually

Now is a good time to be reminded that while UIActivityViewController allows users to perform actions of their choosing, sharing can still be invoked manually, when the occasion arises.

So for completeness, here's how one might go about performing some of these actions manually:

Open URL

if let URL = NSURL(string: "http://nshipster.com") {
    UIApplication.sharedApplication().openURL(URL)
}

NSURL *URL = [NSURL URLWithString:@"http://nshipster.com"];
[[UIApplication sharedApplication] openURL:URL];

System-supported URL schemes include: mailto:, tel:, sms:, and maps:.

Add to Safari Reading List

import SafariServices

if let URL = NSURL(string: "http://nshipster.com/uiactivityviewcontroller") {
    let _ = try? SSReadingList.defaultReadingList()?.addReadingListItemWithURL(URL,
        title: "NSHipster",
        previewText: "..."
    )
}

@import SafariServices;

NSURL *URL = [NSURL URLWithString:@"http://nshipster.com/uiactivityviewcontroller"];
[[SSReadingList defaultReadingList] addReadingListItemWithURL:URL
                                                        title:@"NSHipster"
                                                  previewText:@"..."
                                                        error:nil];

Add to Saved Photos

let image: UIImage = ...
let completionTarget: AnyObject = self
let completionSelector: Selector = "didWriteToSavedPhotosAlbum"
let contextInfo: UnsafeMutablePointer<Void> = nil

UIImageWriteToSavedPhotosAlbum(image, completionTarget, completionSelector, contextInfo)

UIImage *image = ...;
id completionTarget = self;
SEL completionSelector = @selector(didWriteToSavedPhotosAlbum);
void *contextInfo = NULL;
UIImageWriteToSavedPhotosAlbum(image, completionTarget, completionSelector, contextInfo);

Send SMS

import MessageUI

let messageComposeViewController = MFMessageComposeViewController()
messageComposeViewController.messageComposeDelegate = self
messageComposeViewController.recipients = ["mattt@nshipster•com"]
messageComposeViewController.body = "Lorem ipsum dolor sit amet"
navigationController?.presentViewController(messageComposeViewController, animated: true) {
    // ...
}

@import MessageUI;

MFMessageComposeViewController *messageComposeViewController = [[MFMessageComposeViewController alloc] init];
messageComposeViewController.messageComposeDelegate = self;
messageComposeViewController.recipients = @[@"mattt@nshipster•com"];
messageComposeViewController.body = @"Lorem ipsum dolor sit amet";
[navigationController presentViewController:messageComposeViewController animated:YES completion:^{
    // ...
}];

Send Email

import MessageUI

let mailComposeViewController = MFMailComposeViewController()
mailComposeViewController.mailComposeDelegate = self
mailComposeViewController.setToRecipients(["mattt@nshipster•com"])
mailComposeViewController.setSubject("Hello")
mailComposeViewController.setMessageBody("Lorem ipsum dolor sit amet", isHTML: false)
navigationController?.presentViewController(mailComposeViewController, animated: true) {
    // ...
}

@import MessageUI;

MFMailComposeViewController *mailComposeViewController = [[MFMailComposeViewController alloc] init];
mailComposeViewController.mailComposeDelegate = self;
[mailComposeViewController setToRecipients:@[@"mattt@nshipster•com"]];
[mailComposeViewController setSubject:@"Hello"];
[mailComposeViewController setMessageBody:@"Lorem ipsum dolor sit amet"
                                   isHTML:NO];
[navigationController presentViewController:mailComposeViewController animated:YES completion:^{
    // ...
}];

Post Tweet

import Social

let tweetComposeViewController = SLComposeViewController(forServiceType: SLServiceTypeTwitter)
tweetComposeViewController.setInitialText("Lorem ipsum dolor sit amet.")
navigationController?.presentViewController(tweetComposeViewController, animated: true) {
    // ...
}

@import Social;

SLComposeViewController *tweetComposeViewController = [SLComposeViewController composeViewControllerForServiceType:SLServiceTypeTwitter];
[tweetComposeViewController setInitialText:@"Lorem ipsum dolor sit amet."];
[self.navigationController presentViewController:tweetComposeViewController
                                        animated:YES
                                      completion:^{
                                          // ...
                                      }];

IntentKit

While all of this is impressive and useful, there is a particular lacking in the activities paradigm in iOS, when compared to the rich Intents Model found on Android.

On Android, apps can register for different intents, to indicate that they can be used for Maps, or as a Browser, and be selected as the default app for related activities, like getting directions, or bookmarking a URL.

While iOS lacks the extensible infrastructure to support this, a 3rd-party library called IntentKit, by @lazerwalker (of f*ingblocksyntax.com fame), is an interesting example of how we might narrow the gap ourselves.

Normally, a developer would have to do a lot of work to first, determine whether a particular app is installed, and how to construct a URL to support a particular activity.

IntentKit consolidates the logic of connecting to the most popular Web, Maps, Mail, Twitter, Facebook, and Google+ clients, in a UI similar to UIActivityViewController.

Anyone looking to take their sharing experience to the next level should definitely give this a look.

There is a strong argument to be made that the longterm viability of iOS as a platform depends on sharing mechanisms like UIActivityViewController. As the saying goes, "Information wants to be free". And anything that stands in the way of federation will ultimately lose to something that does not.

The future prospects of public remote view controller APIs gives me hope for the future of sharing on iOS. For now, though, we could certainly do much worse than UIActivityViewController.

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2014-04-21-uiactivityviewcontroller.md

2014-04-21-uiactivityviewcontroller.md

UIActivityCategoryAction

UIActivityCategoryShare

Supported Data Types by Activity Type

`<UIActivityItemSource>` & `UIActivityItemProvider`

`<UIActivityItemSource>`

Getting the Data Items

Providing Information About the Data Items

Creating a Custom UIActivity

Invoking Actions Manually

Open URL

Add to Safari Reading List

Add to Saved Photos

Send SMS

Send Email

Post Tweet

IntentKit

Files

2014-04-21-uiactivityviewcontroller.md

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2014-04-21-uiactivityviewcontroller.md

File metadata and controls

UIActivityCategoryAction

UIActivityCategoryShare

Supported Data Types by Activity Type

<UIActivityItemSource> & UIActivityItemProvider

<UIActivityItemSource>

Getting the Data Items

Providing Information About the Data Items

Creating a Custom UIActivity

Invoking Actions Manually

Open URL

Add to Safari Reading List

Add to Saved Photos

Send SMS

Send Email

Post Tweet

IntentKit

`<UIActivityItemSource>` & `UIActivityItemProvider`

`<UIActivityItemSource>`