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The purpose of this post is so that I will have a link to give people when they ask: how do I write an iOS application that pulls data from an RSS feed, displays it pretty and can put things on a map. I'll show you all of that and more as I rewrite my oldest iOS application from scratch: FuelView.
In this post I show two reusable classes for fetching data via HTTP: one that parses the result as XML and another that parses as JSON. These are relatively simple tasks but due to the number of required steps, they can become tiresome if you don't have robust, reusable code for the task. These classes will work on iOS or on the Mac but the optional error alerts and password dialogs are only implemented for iOS.
Background audio in iOS is supposed to be as simple as entering a setting in your Info.plist and making sure your kAudioSessionProperty_AudioCategory is appropriate. This is true unless your audio is part of a movie file or is played in a movie player that has just played video — suddenly it becomes fiddly, hard to test, unreliable and changeable from version to version of iOS.
In this post, I'll look at best practice for using and managing text strings in your user interface. This is a fairly simple topic but Cocoa has established "best practices" for handling user interface strings that new Cocoa developers should be aware of. Since it is inevitably related, I'll also look at the steps involved in localizing the strings in your applications but remember: you should follow good practice for string handling, even if you have no intention of ever translating your application.
After initially starting with a small set of fairly basic media APIs in iPhone OS 2.0, the APIs and the features they provide have dramatically increased in the past 2 years and provided a rapidly moving target for developers trying to remain current. In this post, I'll try to summarize all of the different APIs in iOS 4.3 for playing media, when they arrived, what their purposes are, what their limitations are and what it's been like to remain up-to-date and support new features.
A number of websites are reporting that my application, StreamToMe 3.5 was approved with mention of a piece of future iOS functionality. While this was actually the case, it does not mean that Apple have started accepting apps for this new version of iOS.
In this post, I'll show you the current classes I use to construct and manage UITableViews in a number of different projects. This code is an amalgamation and evolution of some ideas that I've presented in a few earlier posts including my posts on heterogenous cells in a table view and easy custom table view drawing. But this implementation also chooses to do some things differently in an effort to continuously simplify the task of creating customized tables and views in iOS.
In this post, I present a tiny iOS app that generates a continuous tone at a frequency determined by a slider. It's a small sample app intended to show the simplest way to send audio data you generate to the speaker.
In this post, I'll show you ways to determine which version of iOS you are running on and show you how to write a macro that can both conditionally compile and runtime switch between the code for different versions of iOS.
When an application crashes on the iPhone, it disappears without telling the user what happened. However, it is possible to add exception and signal handling to your applications so that an error message can be displayed to the user or you can save changes. It is even possible to try to recover from this situation without crashing at all.
In this post, I look at 5 different ways that you can draw a very simple shape: a square with a triangular hole cut out of the center. In a drawing environment like CoreGraphics which offers double buffering, winding count path filling, even-odd path filling and clipping regions, there's no single answer. An iPhone sample project is provided containing the code but all drawing functions are identical on the Mac.
If your iPhone OS application makes heavy use of the network, there are a few extra settings your application will require to ensure the network works correctly and Apple will approve your application. These requirements are not always obvious (some are documented, others are only implied in documentation). I thought I'd share them so that you can avoid network dropouts and unnecessary App Store rejections.
This week I present some further additions to AudioStreamer, a class I first presented in Streaming and playing an MP3 stream and revisited with bug fixes in Revisiting an old post: Streaming and playing an MP3 stream. This time, I'll add the two of the most requested features: seeking and HE-AAC audio support.
As fast as computers are, heavy use of floating point functions can still slow them down. One way around this, is to use a lookup table instead of calculating floating point values at runtime. But keeping a generated table up-to-date is annoying work. In this post, I'll show you how to create a lookup table automatically using a custom build rule, making an OpenGL animation 5 times faster in the process.
In this post, I present a complete Cocoa Touch iPhone application implemented with unit tests for all created code. I'll look at setting up build and debug targets and executables for both Application and Logic tests, and show you some of the differences between Application and Logic tests. The code for this post is an iPhone version of the Mac post I presented last week.
In this post, I'll discuss iPhone program design using the example of a small but non-trivial iPhone application to provide examples of how the design is implemented. The design includes: how to manage data coming from different sources, how to manage multiple views of that data and how to design your program so it remains simple and manageable as it grows. In short, I'll be discussing how Model-View-Controller (MVC) applies to an iPhone application but I'll also discuss how even simple programs are considerably more hierarchic through their controllers and branched through their models and views than the basic description "Model-View-Controller" might imply.
In this post, I look at a UITableView on the iPhone which loads its data from a server and look at how its performance scales from single rows to tens of thousands of rows. I'll examine which aspects of the iPhone scale well and which become a burden as a displayed dataset moves from trivially sized to large sizes.
It is very easy, when developing on a new operating system, to create projects that won't run on any previous OS version. To ensure backwards compatibility, there are Xcode and gcc options that allow you to build while maintaining support for earlier OS versions. In this post, I'll look at the ways in which this compatibility is controlled and some of the new ways it can go wrong on Snow Leopard.
Shadows can be a useful effect, drawing attention to the content of your view by separating the view from the background. They also look cool. In this post, I'll show you how to add shadows to a UITableView using three CAGradientLayers — one above the first row, one after the last row and one for under the navigation bar.
HTTP is one of the simpler protocols to implement for communication between computers. On the iPhone, since there are no APIs for data synchronization or file sharing, embedding an HTTP server is one of the best ways to transfer data from your iPhone application to a computer. In this post I'll show you how to write your own simple but extensible HTTP server. The server classes will also work on Mac OS X (Cocoa un-Touched).
To celebrate the official release of iPhone OS 3.0 this week, I will show you how to verify that an NSString contains a syntactically valid email address using NSPredicate — a class that joins the iPhone SDK 3.0 as part of the Core Data additions. This code will work on Mac OS X too since, as with the rest of Core Data, NSPredicate has been part of Mac OS X since 10.4 (Tiger).
There is no single-line method for converting between formatting date strings and date objects in Cocoa — the API opts for flexibility rather than simplicity. Unfortunately, this combines with documentation that omits, misdirects and occasionally misinforms, making NSDateFormatter one of the more confusing classes for new Cocoa programmers. In this post, I'll try to address some of the documentation issues and I'll present some methods that will turn NSDate into a formatted string or convert between date strings in a single method.
You can configure your iPhone applications so that a touch in the status bar will scroll a UIScrollView to the top. I'll show you how you can intercept this touch event to use status bar touches for other purposes. The sample application will show a hidden drawer that slides out from the status bar when you tap it.
It is really easy to customize your UITableViews. I'll show you how to completely customize the appearance of UITableViews without overriding or subclassing and without the need for any tricky hackery.
The "Text" (SMS) application on the iPhone uses a custom, semi-transparent view to show its "Sending..." message over the keyboard. I'll show you a simple class that can display semi-transparent loading messages and how you can display messages over the keyboard.
UITableViewController and UIViewController are the two most commonly implemented controllers on the iPhone. It may not always be clear what UITableViewController adds to its superclass. I'll show you what UITableViewController does by recreating its functionality on top of UIViewController and show you why doing this can provide a richer base controller class that you can use throughout your iPhone application.
The UIScrollView and UIPageControl in Cocoa Touch allow for user interfaces with multiple panning pages. The sample project that Apple provides (PageControl) keeps all child views for every page in a lazily loaded array. I'll show you how you can implement this using just two child views, no matter how many virtual pages you wish to represent.
By default, UITableView only supports single-row selection. In this post, I'll show you how to implement multi-row selection, similar to the message edit interface in Mail.
This post looks at writing a UITableViewController for a table view that contains behaviorally unrelated rows — a common occurrence on the iPhone for tables containing multiple groups. I will present a simple alternative to Apple's UITableViewController template code that will reduce complexity and code as well as refocus areas-of-concern for this heterogeneous arrangement.
Automated testing of application user interfaces can be tricky since user interfaces are designed for use by humans not automated tools. The iPhone is particularly challenging since existing tools that aid user interface testing on the Mac are not available. This post will show you a way to run automated, scripted tests on an iPhone app's user interface.
NSXMLDocument is the normal tree-based XML parser in Cocoa. But if you're writing for the iPhone, this class isn't available. Even on the Mac, sometimes you want tree-based parsing without the full overhead of NSXMLDocument. Here's how to use libxml2 to perform tree-based parsing in a Cocoa-friendly way.
The iPhone lacks specific methods to create UIEvent and UITouch objects. I'll show you how to add this functionality so you can write programmatically driven user-interfaces.
