My App Inside Imessage Uiactivityviewcontroller

My app inside iMessage UIActivityViewController

Instead of a URL scheme you need to add a document type to your app. Try adding the following fragment to your Info.plist:

<key>CFBundleDocumentTypes</key>
<array>
    <dict>
        <key>CFBundleTypeName</key>
        <string>public.jpeg</string>
        <key>CFBundleTypeRole</key>
        <string>Editor</string>
        <key>LSHandlerRank</key>
        <string>Owner</string>
        <key>LSItemContentTypes</key>
        <array>
            <string>public.jpeg</string>
        </array>
    </dict>
</array>

With this fragment (specifically with the LSItemContentTypes key) you declare that your app is an editor for documents that have the Uniform Type Identifier (UTI) public.jpeg. Because this UTI is declared by the system, I believe it is not necessary that you include the UTI declaration in your app's Info.plist.

You can find all system-declared UTI's in the Apple document titled System-Declared Uniform Type Identifiers. If you are new to UTI you should probably also read the Apple document Uniform Type Identifier Concepts.

Last but not least, don't forget to consult the Information Property List Key Reference to find out what you should specify for the Core Foundation keys CFBundleTypeRole and LSHandlerRank.

BTW: This excellent SO answer also has details about working with UTIs, especially if you ever need to declare your own app-specific UTI.

Why does iMessages change the URL I pass to it via the UIActivityViewController?

When the url is passed to iMessages, it retrieves the web site in order to render a preview.

At the top of the page returned is:

<link rel="canonical" href="https://app.acuityscheduling.com/schedule.php?owner=12808744">

This says that the canonical link for this page is https://app.acuityscheduling.com/schedule.php?owner=12808744, and so the activity item is updated with this, preferred, url for the page.

UIActivityViewController cannot add image to imessage

As others have said, iMessage only supports text, not images. Although it sounds like in iOS7, it does work.

I know personally I've gotten it to work with OvershareKit: https://github.com/overshare/overshare-kit .

It of course adds a bit of overhead but allows you to share with just about every medium there is with their slick interface/APIs.

UIActivityViewController not showing Message option When Sharing Image Object

Your code is completely fine, works to me.

First of all you Messages app may be missing if you have iMessage disabled in your settings. Go to Settings->Messages and make sure it's on:

Also you may not see it in the default items, check out hidden ones:

Basic example for sharing text or image with UIActivityViewController in Swift

UIActivityViewController Example Project

Set up your storyboard with two buttons and hook them up to your view controller (see code below).

Sample Image

Add an image to your Assets.xcassets. I called mine "lion".

Sample Image

Code

import UIKit
class ViewController: UIViewController {
    
    // share text
    @IBAction func shareTextButton(_ sender: UIButton) {
        
        // text to share
        let text = "This is some text that I want to share."
        
        // set up activity view controller
        let textToShare = [ text ]
        let activityViewController = UIActivityViewController(activityItems: textToShare, applicationActivities: nil)
        activityViewController.popoverPresentationController?.sourceView = self.view // so that iPads won't crash
        
        // exclude some activity types from the list (optional)
        activityViewController.excludedActivityTypes = [ UIActivity.ActivityType.airDrop, UIActivity.ActivityType.postToFacebook ]
        
        // present the view controller
        self.present(activityViewController, animated: true, completion: nil)
        
    }
    
    // share image
    @IBAction func shareImageButton(_ sender: UIButton) {
        
        // image to share
        let image = UIImage(named: "Image")
        
        // set up activity view controller
        let imageToShare = [ image! ]
        let activityViewController = UIActivityViewController(activityItems: imageToShare, applicationActivities: nil)
        activityViewController.popoverPresentationController?.sourceView = self.view // so that iPads won't crash
        
        // exclude some activity types from the list (optional)
        activityViewController.excludedActivityTypes = [ UIActivity.ActivityType.airDrop, UIActivity.ActivityType.postToFacebook ]
        
        // present the view controller
        self.present(activityViewController, animated: true, completion: nil)
    }
    
}

Result

Clicking "Share some text" gives result on the left and clicking "Share an image" gives the result on the right.

Sample Image

Notes

I retested this with iOS 11 and Swift 4. I had to run it a couple times in the simulator before it worked because it was timing out. This may be because my computer is slow.
If you wish to hide some of these choices, you can do that with excludedActivityTypes as shown in the code above.
Not including the popoverPresentationController?.sourceView line will cause your app to crash when run on an iPad.
This does not allow you to share text or images to other apps. You probably want UIDocumentInteractionController for that.

My App Inside Imessage Uiactivityviewcontroller