iOS 8 added a lot of new functionality and APIs. Along the way, several things have changed. Here are a few items I’ve come across:

Documents and Library

UPDATE: Xamarin.iOS now handles getting the folder path correctly when using Environment.SpecialFolder in iOS 8 as well.

Prior to iOS8 it was common for Xamarin.iOS applications to access folder paths using the .NET System.Environment class, which on iOS provided a familiar abstraction around native system folders. For example, you could get to the documents folder like this:

var docs = Environment.GetFolderPath (
  Environment.SpecialFolder.MyDocuments);

However, in iOS 8 the location of some folders, namely the Documents and Library folders, has changed such that they are no longer within the app’s bundle.

Apple describes the changes in Technical Note TN2406.

The proper way of determining the location of these folders is to use the NSFileManager. For example, get the location of the Documents folder as follows:

var docs = NSFileManager.DefaultManager.GetUrls (
  NSSearchPathDirectory.DocumentDirectory, 
  NSSearchPathDomain.User) [0];

Location Manager

To use location in iOS you go through the CLLocationManager class. Before iOS 8 the first time an app attempted to start location services the user was presented with a dialog asking to turn location services on. You could set a purpose string directly on the location manager to tell the user why you need location in this dialog.

In iOS 8 you now have to call either RequestWhenInUseAuthorization or RequestAlwaysAuthorization on the location manager. Additionally you need to add either the concisely named NSLocationWhenInUseUsageDescription or NSLocationAlwaysUsageDescription to your Info.plist. Thanks to my buddy James for tracking these down.

AVSpeechSynthesizer


The AVSpeechSynthesizer was added in iOS 7, allowing apps to deliver text to speech functionality with just a few lines of code, like this:

var speechSynthesizer = new AVSpeechSynthesizer ();

var speechUtterance = new AVSpeechUtterance (text) {

  Rate = AVSpeechUtterance.MaximumSpeechRate/4,

  Voice = AVSpeechSynthesisVoice.FromLanguage ("en-US"),

  Volume = 1.0f

};


speechSynthesizer.SpeakUtterance (speechUtterance);

The above code worked on either the simulator or a device prior to iOS 8. However, when run on an iOS 8 simulator, you are now greeted with the following error message:

Speech initialization error: 2147483665

However it does appear to work on a device. There is an open bug here: http://openradar.appspot.com/17299966

Thanks to René Ruppert for discovering this. Incidentally, René has a blog post on a few other iOS 8 issues worth checking out: http://krumelur.me/2014/09/23/my-ios8-adventure-as-a-xamarin-developer/

Input Accessory Views

Before iOS 8 you could set the InputAccessoryView on a UITextField from a view contained in another controller.

aTextField.InputAccessoryView = aViewController.SomeView;

While this worked before iOS 8, it did not guarantee the view controller hierarchy would be set up properly. A better approach, even before iOS 8, would be to set the InputAccessoryView directly to an instance of UIView subclass, not one contained in another UIViewController. Practically speaking, people would take the view controller approach because it let them set things up via a xib. Therefore, to handle the view controller case, iOS 8 introduced the InputAccessoryViewController property on UIResponder. It’s still easier to just use a UIView subclass imho, but if you need to use a UIViewController, set it to InputAccessoryViewController.

Action Sheets

Apple states in their documentation that you should not add a view to a UIActionSheet’s view hierarchy. Before iOS 8 adding subviews to a UIActionSheet would actually work, although it was never the intention (nor should it be subclassed). Code that took this approach should have presented a view controller.

In iOS 8 subclassing UIActionSheet or adding subviews to it will no longer work. Additionally UIActionSheet itself has been deprecated. Instead, you should use a UIAlertController in iOS 8 (UIAlertController should also be used in iOS 8 in place of the deprecated UIAlertView) as I discussed in my iOS 8 webinar.