iphone Programming Patrick H. Madden SUNY Binghamton Computer Science Department

Transcription

1 iphone Programming Patrick H. Madden SUNY Binghamton Computer Science Department

2 General Outline Overview of the tools, and where to get more information Quick get-up-and running hello world examples Objective C syntax quirks Full featured macro block placement tool iphone app autopsy

3 Where to Find Information developer.apple.com Vast amounts of information available; programming guides, tutorials, sample application programs, technical forums full of smart people stackoverflow.com -- also very useful forums If you run into a problem, a few minutes of Google searching will likely turn up an answer...

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6 The Major Components XCode -- a full featured IDE XCode will generate the make files and much of the template code for you. Take advantage of this. You do not want to do this on your own. Variable and function name completion, continuous syntax checking, lots of live links to documentation Integrated Objective-C compiler and debugger (actually gcc and gdb) Objective-C is required for the user interface, but you can link in C or C++ fairly easily User interface construction tool Interface Builder -- drag and drop widgets and screens iphone and ipad simulator Code is compiled to x86 architecture, and leverages the widgets from Mac OSX Good for debugging, but multi-touch is not well supported iphone and ipad native testing and distribution Requires paid developer membership ($99 a year) Code is cross-compiled to ARM, with the ios widgets acting in the same manner as the MAC OSX variants Debugging and troubleshooting can be done over USB Membership gets you encryption keys to allow distribution through itunes or an ad hoc program (maximum of 100 devices)

7 Exercise 1: Hello World Start up XCode, create a new project Add a label that says hello world to the main screen Compile and run...

8 Select View-based application, and click next a few times (you ll be asked for the project name, and where to store it on your disk).

9 XCode will generate templates, and also all the configuration to build an executable. The user interface is chock-full of tabs, toggle boxes, and has an integrated editor.

10 Select example1viewcontroller.xib 2. Open the toolbox panel (if not already open) 3. Select objects for the toolbox (if not already selected)

11 Drag a label object onto the view, and edit the text as needed...

12 Click the run button... XCode compiles the code, starts the iphone simulator, and launches your app.

13 Some Details The editor window where we dragged the label onto the view is Interface Builder. The full integration into XCode is a recent change. Interface builder is watching your source code files, and is indexing things frequently. We ll need to give it hints for things to look for... The xib file defines the visual appearance of a window. It is compiled into a nib file that is loaded at run time. Loading a nib file is a way to create a set of objects. The objects are then what one sees during run time.

14 Expanded Example Example2 starts where Example1 ended. Edit example2viewcontroller.h to add an instance variable and a method.

15 Instance variable How the variable is accessed Method for the class Keywords that Interface Builder looks for

16 In example2viewcontroller.m, add in line. Object C objects need functions to get or set variables -- this line causes those functions to be automatically generated. At the bottom of the file (before add in the method to update the hello message.

17 Back in example2viewcontroller.xib, Interface Builder has some new information. Click on File s Owner and the class information tab; note that it is an example2viewcontroller class Right click on File s Owner, and you will see the instance variable and method are available. The syntactic sugar of IBAction and IBOutlet make this possible.

18 Right click (or control click) on Files Owner Note that we have the outlet label and a recieved action changemessage Click and drag by one of the circles to connect an instance variable to an object, or an event to a method.

19 Drag a button object into the view, and edit the label. Use right-click to open up a menu on the button; connect touch up inside to File s Owner changemessage Right click on File s Owner to open a menu; connect the instance variable label to the UILabel object in the view. Compile and run; clicking the button changes the message...

20 Figure 2-2 Application life cycle UIKit Your code User taps application icon main() UIApplicationMain() application: didfinishlaunchingwithoptions: Event Loop Handle event System asks application to quit foreground applicationwillresignactive: Application moves to background applicationdidenterbackground: figure from: Apple iphone App Programming Guide

21 Figure 2-7 Processing events in the main run loop Event source Port Event queue Main run loop Operating system Application object Core objects figure from: Apple iphone App Programming Guide

22 Objective C Syntax Quirks This will look a little strange until you get used to it... But there are no fundamentally new concepts to wrap your mind around. The biggest difference with C++ or Java is in where you put brackets, commas, and so on...

23 Objective C Objects Roots of the language go back to the company StepStone. NeXT acquired the technology, creating NeXTStep. The prefix of NS shows up in many places. Nothing exotic in the Object-Oriented paradigm Each object has a set of methods that operate on it. Communication between objects is with messages. Most of the time, the messages are really function calls. Single inheritance; all Objective-C objects derive from the root NSObject class Very good support for run time linking, querying to see if an object belongs to a class or implements a particular interface. Very very good memory management. More on this later.

24 Objective C Objects figure from: Objective C Programming Guide

25 Objective C Syntactic Sugar Use #import instead of #include Includes the file once and only once Class interface is defined in the.h file (wrapped Class implementation is defined in the.m file (wrapped

26 Method Declarations -(int)foo:(int)arga second:(int)argb; Beginning minus sign indicates an instance method (+ indicates class method) Spaces between arguments, rather than commas. Each argument (after the first) has a name that is used when the method is called. Much more verbose than C or C++. Call the above with [objectname foo:44 second:57]; In many places, dot notation is also allowed. For getting the text from a label, we could use either [label text] or label.text (both of which return an NSString).

27 Calling a method is done by placing square brackets. Arguments are prefixed with colons. The settext method of the object label is sent the Objective C string I said hello! More details on in a moment... Instance variables in objects are accessed with setter and getter methods. The settext method is likely tied to an instance variable called text. The method was likely created by compiler directive. Note that variables, methods, etc., are picketfencecapitalization. Case does matter, and Objective C encourages this style of coding.

28 Memory Management Objective C objects keep track of the number of pointers that reference them Each object has a retain reference count If you point to an object X (and want to make sure that it stays around), you must do [X retain]. When you re done, [X release]. When the retain count of an object reaches zero, it deallocates itself automatically. The mechanism is simple and effective, and a bit easier that a do-it-yourself approach, but you still have to be careful. Remember (nonatomic, retain) line? This tells XCode to synthesize setter and getter methods, and to automatically retain the instance variables... Instead of retain, you could use assign

29 Creating New Objects Create new objects for a class by using the class name and alloc. Most classes require initialization. ClassName *c = [[ClassName alloc] init]; Be aware of how retain works; if you don t retain objects, they might get garbage collected unexpectedly.

30 Strings In Objective C, traditional zero-terminated ASCII strings (C style strings) are rarely used. Instead, use NSString objects (created automatically Some string ). The NSString class supports a wide range of conversion, comparison, parsing, etc., methods. Using a C-style string in place of an NSString will likely crash your application. They are NOT interchangeable

31 Model-View-Controller The Apple user interface paradigm is build on the Model- View-Controller concept The model is the set of instance variables in an object. For example, it might be a floating point number for temperature. The view is how the model is presented to the user. It could be a number, a thermometer gauge, a dial, a color, and so on. The controller is the code that links the model and view together. If the floating point value changes, the controller is responsible for updating the user interface

32 How MVC Works in the ios Universe The top level object of an app is the App Delegate -- it handles messages informing of start-up, shut down, etc. An App Delegate must have a View Controller object. This object handles touch events, and must also have a view object that it can pass to the ios rendering engine. The view maintains a hierarchy of objects (each view can contain subviews). Event messages get relayed to the appropriate object, and the methods for those objects get called as needed. Each object either uses the built-in rendering routines, or can perform custom rendering by overriding the drawrect method.

33 Figure 2-3 Launching into the active state Launch the application Load main nib and create application delegate Application Delegate Initialize the application application: didfinishlaunchingwithoptions: Application enters the foreground applicationdidbecomeactive: figure from: Apple iphone App Programming Guide

34 Example 3 - Macro Block Placement Start a new project, and create a new class called MacroBlock Select file/new-file or right-click on the project folder in XCode Click through, selecting UIImageView as the parent class, and giving MacroBlock as the name

35 In MacroBlock.h, add in instance variables for the parent view, and also variable to hold the screen location.

36 In MacroBlock.m, add in methods to handle touch events. You do not need to declare them in the.h file; our parent class, UIImageView, already has them declared. Our derived class is simply overriding the default methods.

37 In the view controller (example3viewcontroller.m), there is a viewdidload method; it gets called after the application launches. We ll create 10 new macro blocks, and insert them on the screen. We can color them red, so that they show up against the background. We also set the user interaction field for the objects, and let them know what view they are part of.

38 Exercise for Later You could keep pointers to each macro block object, and query the location. Add a button to the screen, and a label When you click the button, compute the Half Perimeter Wire Length that contains the macro blocks...

39 Anatomy of an App iphone apps are distributed in as.ipa files And under the hood... it s just a zip archive. You can open these up, and look inside... Inside a payload directory are a variety of files that ios uses when your application launches

40 An unzipped App itunesartwork is exactly what you might expect it to be; a PNG file that gets displayed in itunes

41 itunes Metadata. The app knows who bought it.

42 An iphone or OSX application is really a directory (where the contents are normally hidden). Show package contents reveals all.

43 Within the app directory should be an Info.plist file. Take a look in XCode in the Supporting Files folder; there s an example3-info.plist which specifies the icons, executable name, and so on. None of this is magic, but it s fairly well hidden from the average user.

44 There s much much more... Complex widgets -- maps, Web interfaces, tables,... Multi-touch wizardry... Protocols and delegates... Local file storage, GameKit, audio processing, accelerometers and GPS...

45 Final Thoughts... Stick with the MVC controller paradigm; it s easier to adapt yourself to ios than vice versa RTFM. There really is plenty of available documentation Have fun. iphone hacking is the most fun I ve had since my Sinclair ZX-81...