Understanding the Limits of UIActivityViewController

When it comes to sharing content from an app, UIActivityViewController is a popular choice for creating a seamless and intuitive user experience. However, there are some limitations and gotchas associated with this class that can lead to unexpected behavior if not handled correctly.

In this article, we’ll delve into the world of UIActivityViewController, exploring its capabilities, limitations, and potential pitfalls. Specifically, we’ll focus on the issue of service names not appearing in the service picker when using UIActivityViewController to share an image from an app.

What is UIActivityViewController?

For those unfamiliar with UIActivityViewController, let’s take a brief look at what this class provides. UIActivityViewController is a view controller that allows users to select one or more activities (such as sending an email, posting on Facebook, or saving an image) from a list of available options. This class was introduced in iOS 4.1 and has since become a staple in many app development projects.

When you create an instance of UIActivityViewController, you provide it with an array of activity items to share, such as images, URLs, or text. The view controller then displays a service picker that allows the user to select the desired activity. Once selected, the chosen activity is executed, passing the provided data along.

Creating a UIActivityViewController Instance

To create an instance of UIActivityViewController, you need to initialize it with an array of activity items and any additional application activities (if required). In our example, we’re only sharing an image, so we provide a single item:

UIImage *sourceImage = [[UIImage alloc] initWithContentsOfFile:[[self currentMedia] path]];
NSArray *activityItems = @[sourceImage];
UIActivityViewController *avc = [[UIActivityViewController alloc] initWithActivityItems:activityItems applicationActivities:nil];

Note that the applicationActivities parameter is optional and can be used to provide additional activities, such as email or social media options.

Setting Excluded Activity Types

One of the common use cases for UIActivityViewController is to exclude certain activity types from being displayed in the service picker. For example, you might want to prevent users from printing or copying content that’s not relevant to your app. To achieve this, you can set the excludedActivityTypes property:

avc.excludedActivityTypes = [NSArray arrayWithObjects:UIActivityTypePrint, UIActivityTypeCopyToPasteboard, UIActivityTypeAssignToContact, UIActivityTypeSaveToCameraRoll, nil];

This ensures that these activities are not displayed in the service picker, giving your app more control over the sharing experience.

Presenting the View Controller

Once you’ve created and configured your UIActivityViewController instance, you can present it using a standard presentViewController:animated:completion: call:

[self presentViewController:avc animated:YES completion:nil];

Note that we don’t need to worry about releasing the view controller or individual activity items since we’re using ARC (Automatic Reference Counting).

The Issue with Service Names

Now, let’s get back to the original question. The user is experiencing an issue where service names like Email, Twitter, and Facebook are not appearing in the service picker. To understand why this might be happening, we need to delve into the inner workings of UIActivityViewController.

When you create a UIActivityViewController instance, it uses a combination of system-provided data and user-defined settings to determine which activities should be displayed in the service picker. One key piece of information that determines activity types is the user’s preferred activity types.

Preferred Activity Types

The user’s preferred activity types are stored in their default preferences within the Settings app. These preferences are then used by various system apps, including UIActivityViewController, to determine which activities should be displayed when sharing content.

However, it seems that there might be a discrepancy between what is being expected and what is actually happening. In our case, the user has chosen to exclude certain activity types from being displayed in the service picker (as we set in excludedActivityTypes). But for some reason, these excluded activities are still appearing in the picker.

Why Are Excluded Activities Appearing?

There are a few possible explanations for why this might be happening:

• The user has chosen to include these activities in their preferred activity types despite setting them to be excluded.
• There is an issue with how UIActivityViewController is accessing or interpreting the system-provided data that determines activity types.
• The excluded activities are somehow being flagged as “optional” or “recommended” within UIActivityViewController, causing them to appear in the service picker despite being excluded.

A Different Approach

Given these issues, a different approach might be necessary. One option is to switch to Automatic Reference Counting (ARC) for your project. While this requires more work upfront, it can simplify many of the issues related to memory management and provide additional benefits like automatic memory cleanup.

Another potential solution is to make UIActivityViewController a retained instance property within your app. This would prevent instances from being released prematurely, potentially resolving any issues related to activity types not appearing in the service picker.

Conclusion

While UIActivityViewController provides a powerful way to share content and enable intuitive user experiences, there are limitations and potential pitfalls associated with this class. By understanding how it works and the factors that influence its behavior, you can better navigate these complexities and create a seamless sharing experience for your users.

In our example, we explored an issue where service names were not appearing in the service picker despite excluding certain activities. We discussed possible explanations for why this might be happening and provided potential solutions to mitigate these issues.

Last modified on 2024-03-31