Sunday 23 September 2012

iOS 6 UIRefreshControl with MonoTouch

Another cute little new feature of iOS 6 is the built-in pull-to-refresh control - UIRefreshControl. It is really simple to wire up with Xamarin on a regular UITableViewController or with MonoTouch.Dialog.

In case you're unfamiliar with it, this is how the new control looks:

To implement:

  • Assign the RefreshControl property of a UITableViewController to a new instance of the control, eg. RefreshControl = new UIRefreshControl();
  • Create a handler for the control's ValueChanged event, eg RefreshControl.ValueChanged += HandleValueChanged;. In this handler your code will do whatever is required to refresh the data when the user pulls down enough to trigger the event.
  • In HandleValueChanged code, once you have refreshed the table, call the EndRefreshing method of the control to stop it spinning. Your refresh code was probably not running on the main thread, in which case you'll probably want to use InvokeOnMainThread like this: InvokeOnMainThread (() => {RefreshControl.EndRefreshing (); });

There are additional features you may use:

  • BeginRefreshing - call this method from your code if you start a refresh operation from code (eg. on a timer or in response to some other event). This sets the UI of the control to indicate there is already a refresh in progress.
  • Refreshing - whether there is already a refresh in progress.
  • AttributedTitle - optional text that appears under the refresh control.
  • TintColor - customize the appearance of the control to match your application's theme.

Refer to Apple's UIRefreshControl doc for additional info.

UPDATE: What about iOS 5?

This above example will not work on earlier versions of iOS - the UIRefreshControl class does not exist, nor does the RefreshControl property on UITableViewController. To get around this problem, the following code does a system check and falls back to an old-fashioned navbarbutton in earlier versions of iOS:

if (UIDevice.CurrentDevice.CheckSystemVersion (6,0)) {
    // UIRefreshControl iOS6
    RefreshControl = new UIRefreshControl();
    RefreshControl.ValueChanged += (sender, e) => { Refresh(); };
} else {
    // old style refresh button
    NavigationItem.SetRightBarButtonItem (new UIBarButtonItem (UIBarButtonSystemItem.Refresh), false);
    NavigationItem.RightBarButtonItem.Clicked += (sender, e) => { Refresh(); };

The Refresh method should contain the code that actually gets new data and updates the UITableView. That method should contain a similar if (CheckSystemVersion(6,0)) clause that wraps the call to the RefreshControl.EndRefreshing method on the main thread. Users on older operating systems will see this:

Wednesday 19 September 2012

iOS 6 released, supported by Xamarin

It would be hard to miss the news that Apple is launching their new iPhone 5 this week, and has also released the final version of iOS 6. What's also great is that Xamarin supports iOS 6 too, on release day! There's already plenty of documentation, using C# with StoreKit, PassKit, EventKit, UIKit changes and more.

Of course there are heaps of little additions as well as those big ones, including a raft of new Core Image Filters to play with. For those working on the next Instagram (isn't everyone ;-), here's a preview of a couple of them:

(Posterize, Bloom, Invert, Perspective and Vortex)

For more information, review the Introduction to CoreImage in iOS 5 and the additional sample code for iOS 6. You might also like Apple's CoreImage Filter Reference.

Thursday 13 September 2012

Microsoft's Azure Mobile Services... and WP7... and Mac

So far, Azure Mobile Services have been added to MonoTouch and Mono for Android (as well as Microsoft's getting started sample for Windows 8).
To complete the 'set', I ported the MonoTouch code to MacOSX using the free, open-source MonoMac AND used @kenegozi's 'unofficial' client to munge Azure Mobile Services into our existing Tasky sample on WP7.

These aren't production-quality implementations, mind you, just a couple of quick hacks to illustrate the beauty and simplicity of having C# and the .NET framework available across all these platforms. Oh, and also show the beauty of Azure Mobile Services :-)
You can grab the code for all of these from TaskCloud/Azure on github. You'll need to sign up for the Azure trial and follow the instructions to set up the Todo list tutorial.
Here's how the WP7 and MonoMac versions look:

Saturday 1 September 2012

Microsoft's Azure Mobile Services... and Mono-for-Android

Yesterday's post introduced a quick implementation of Microsoft's Azure Mobile Services using MonoTouch to build an iOS app.
The WebClient and Json handling was easily refactored into a single class - AzureWebService - which was then added to the existing Android version of the Tasky sample... and now we have the same Azure Mobile Service being access by three platform clients: Windows 8, iOS and Android all with C# (and the iOS and Android apps sharing the service client code).

Additional features have also been added to AzureWebService to allow deletion of tasks. The Android app source is on github and it looks like this (delete has been added to the iOS app too):

Here is a discussion of how the API was reverse-engineered with Fiddler. The REST endpoints that TaskyAzure accesses are:

GET /tables/TodoItem

GET /tables/TodoItem/?$filter=(id%20eq%20{0})

PATCH /tables/TodoItem/{id}
{"id":1,"text":"updated task text","complete":false}

POST /tables/TodoItem
{"text":"new task text","complete":false}

DELETE /tables/TodoItem/{id}

Finally, only a few small updates were required in the Windows 8 example prevent the completed tasks from disappearing and instead make use of the checkbox in a more natural way:

Now all three apps are reading and writing to the same Azure data store! Can't wait for the official cross-platform APIs :-)