Share to social media on iOS with UIActivityViewController

From UIViewController to screenshot to social media.

Send your shares into space. Source: Oliver K. Ernst (author). License: Attribution-NonCommercial-NoDerivatives 4.0 International

The problem:

You want to implement a share button that takes a screenshot from your app and let’s users share it to social media.


  • You want to create a custom image by creating a custom UIViewController.
  • You don’t want the UIViewController to show.
  • You want to show a nice preview of the image that you’ll share.

You cant find the complete project on GitHub here.

Let’s get started with a clean project.

Project setup

Let’s start with a clean project. Add a share button to the default view controller. For the button image, you can choose square.and.arrow.up to make it look like a native share button.

Add a new view controller which will produce the image to be shared. Do not add a segue from the old view controller to the new one — this will be done programmatically.

Change it’s size to be a custom value in the Size inspector by selecting Freeform and entering the size.

Also make sure you uncheck **Resize View From Nib**in the Attributes inspector.

Else the custom size will not appear when we instantiate the view controllor.

Add a new class for this view controller called ShareViewController and assign it in the storyboard. Also give it the Storyboard ID: shareVC .

You can add whatever you want to the view controller.

Taking the screenshot

First, let’s make a simple implementation for the ShareViewController :

It updates the message field, and provides a simple populate method for that task (very important if you have non-trivial data types to separate the GUI and logic!).

The most important method is the one that takes the screenshot — without showing the **ShareViewController**:

  • First, instantiate the view controller. You don’t need to push it to the navigation controller, since we don’t want to show it.
  • Next, begin taking the screenshot with UIGraphicsBeginImageContextWithOptions . Pass the vc.view.frame.size such that it uses the same size as the ShareViewController . The 3.0 factor is a scaling factor to increase the quality of the image — you will need to dial this in depending on the size of your ShareViewController .
  • Next, populate the ShareViewController with the data.
  • Render the image with vc.view.layer.render(in: UIGraphicsGetCurrentContext()!) . This creates the screenshot from the view controller without showing it.
  • Finally, create an image from the context and return it. Don’t forget to call UIGraphicsEndImageContext!

Sharing to social media

Next, in the main ViewController , hook up a short method to the share button:

Here, share is implemented as follows:

  • First we take the screenshot, obtaining a UIImage using the take_screen_shot method.
  • Next we set the filename. Note that this is also visible to the user in the activity view controller. Every time the user shares, this image will be overwritten — so it is not taking up too much space on the phone.
  • Next store the image and get it’s URL.
  • Create the UIActivityViewController , passing the URL to share.
  • Set the excluded activities — there’s lots to choose from here, but probably you don’t want the reading list option.
  • Finally, present the view controller.

We already did the screen shot method. Next, the save image method:

which should be self-explanatory.

The only missing method is the error message:

This, too, should be self-explanatory.


Let’s see how it turned out — pressing the button gives:

As we can see, there’s a preview of the image we’re sharing. The image is:

Final thoughts

Note that not all of the buttons may work correctly. For example, if you choose Save Image , you may get:

**This app has crashed because it attempted to access privacy-sensitive data without a usage description. The app's Info.plist must contain an NSPhotoLibraryAddUsageDescription key with a string value explaining to the user how the app uses this data.**

So… do that!

You cant find the complete project on GitHub here.

Happy sharing!


Oliver K. Ernst
October 9, 2020

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