Introduction to iOS 6

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iOS 6 includes a variety of new technologies for developing apps, which Xamarin.iOS 6 brings to C# developers.

Overview

With iOS 6 and Xamarin.iOS 6, developers now have a wealth of capability at their disposal to create iOS applications, including ones that target iPhone 5. This document lists some of the more exciting new features that are available and links to articles for each topic. In addition it touches on a couple changes that will be important as developers move to iOS 6 and the new resolution of iPhone 5.

Introduction to Collection Views

Collection Views allow content to be displayed using arbitrary layouts. They allow easily creating grid-like layouts out of the box, while supporting custom layouts as well. For more information see, the Introduction to Collection Views guide.

Introduction to Pass Kit

The Pass Kit framework allows applications to interact with digital passes that are managed in the Passbook app. For more information see, the Introduction to Pass Kit guide.

Introduction to Event Kit

The EventKit framework provides a way to access the Calendars, Calendar Events, and Reminders data that Calendar Database stores. Access to the calendars and calendar events has been available since iOS 4, but iOS 6 now exposes access to reminders data. For more information, see the I ntroduction to EventKit guide.

Introduction to the Social Framework

The Social Framework provides a unified API for interacting with social networks including Twitter and Facebook, as well as SinaWeibo for users in China. For more information see, the Introduction to the Social Framework guide.

Changes to Store Kit

Apple has introduced two new features in Store Kit: purchasing and downloading iTunes or App Store content from within your app, and hosting your content files for in-app purchases!. For more information see, the Changes to Store Kit guide.

Other Changes

ViewWillUnload and ViewDidUnload Deprecated

The ViewWillUnload and ViewDidUnload methods of UIViewController are no longer called in iOS 6. In previous versions of iOS, these methods may have been used by applications for saving state before a view unloads, and cleanup code respectively.

For example, Xamarin Studio would create a method called ReleaseDesignerOutlets, shown below, which would then be called from ViewDidUnload:

void ReleaseDesignerOutlets ()
{
    if (myOutlet != null) {
        myOutlet.Dispose ();
        myOutlet = null;
    }
}

However, in iOS 6, it is no longer necessary to call ReleaseDesignerOutlets.

For cleanup code, iOS 6 applications should use DidReceiveMemoryWarning. However, code that calls Dispose should be used sparingly and only for memory intensive objects as shown below:

if (myImageView != null){
    if (myImageView.Superview == null){
        myImageView.Dispose();
        myImageView = null;
    }
}

Again, calling Dispose as above should rarely be needed. In general the most applications should do is to remove event handlers.

For the case of saving state, applications can perform this in ViewWillDisappear and ViewDidDisappear instead of ViewWillUnload.

iPhone 5 Resolution

iPhone 5 devices have a 640x1136 resolution. Applications that targeted previous versions of iOS will appear letterboxed when run on an iPhone 5, as shown below:

In order for the application to appear full-screen on iPhone 5, simply add an image named Default-568h@2x.png having a resolution of 640x1136. The following screenshot shows the application running after this image has been included:

Subclassing UINavigationBar

In iOS 6 UINavigationBar can be subclassed. This allows additional control of the look and feel of the UINavigationBar. For example, applications can subclass to add subviews, animate those views and modify the Bounds of the UINavigationBar.

The code below shows an example of a subclassed UINavigationBar that adds a UIImageView:

public class CustomNavBar : UINavigationBar
{
​    UIImageView iv;
    public CustomNavBar (IntPtr h) : base(h)
​    {
​​        iv = new UIImageView (UIImage.FromFile ("monkey.png"));
​​        iv.Frame = new CGRect (75, 0, 30, 39);
​    }
    public override void Draw (RectangleF rect)
​    {
​​        base.Draw (rect);
        TintColor = UIColor.Purple;
​​        AddSubview (iv);
​    }
}

To add a subclassed UINavigationBar to a UINavigationController, use the UINavigationController constructor that takes the type of the UINavigationBar and UIToolbar, as shown below:

navController = new UINavigationController (typeof(CustomNavBar), typeof(UIToolbar));

Using this UINavigationBar subclass results in the image view being displayed as shown in the following screenshot:

Interface Orientation

Prior to iOS 6 applications could override ShouldAutorotateToInterfaceOrientation, returning true for any orientations the particular controller supported. For example, the following code would be used to support only portrait:

public override bool ShouldAutorotateToInterfaceOrientation (UIInterfaceOrientation toInterfaceOrientation)
    {
        return (toInterfaceOrientation == UIInterfaceOrientation.Portrait);
    }

In iOS 6 ShouldAutorotateToInterfaceOrientation is deprecated. Instead applications can override GetSupportedInterfaceOrientations on the root view controller as shown below:

public override UIInterfaceOrientationMask GetSupportedInterfaceOrientations ()
    {
        return UIInterfaceOrientationMask.Portrait;
    }

On iPad, this defaults to all four orientations if GetSupportedInterfaceOrientation is not implemented. On iPhone and iPod Touch, the default is all orientations except PortraitUpsideDown.

Xamarin Workbook

If it's not already installed, install the Xamarin Workbooks app first. The workbook file should download automatically, but if it doesn't, just click to start the workbook download manually.