TouchThatFruit

iOS development tips, tricks, news and opinions learned along the way of one London developer

[touchthatfruit-blog]

Memory leaks in Instruments after converting to ARC

I decided to convert a project which was mostly fine in terms of memory management to use ARC. After the converstion I wanted to check that everything is fine in Instruments and I couldn't believe what I saw. Virtually everything was leaking! But why? In some of the classes I even set breakpoints inside init and dealloc methods and counted how many times do things get created and deallocated. That seemed to be just fine. Where was the problem than?

The debug build I was running in the simulator was indeed perfecly fine. However the build Instruments were using apparently didn't have ARC enabled and hence everything was leaking.

If you encounter a similar problem go to the build setting of the target that's causing the problems and check the highlighted setting to be all set to yes. In my case the green flags were just fine, set to -fobjc-arc indicating ARC should be on. However the red ones were not for the release build and that is what caused all the problems. After changing everything to YES memory leaks disappeared.

[touchthatfruit-blog]

Playing music in your app - MediaPlayer tutorial

In this tutorial we will have a look at how to use MediaPlayer framework to play music from your app. To begin with we need to#import <MediaPlayer/MediaPlayer.h>. There are three core classes that we will work with.

MPMusicPlayerController There are two types of MPMusicPlayerController

Application music player ([MPMusicPlayerController applicationMusicPlayer]) that plays music just in your app and does not affect the in-built iPod

iPod music player ([MPMusicPlayerController iPodMusicPlayer]) that employs the in-built iPod to play music - the music can be controlled in the iPod app and remains playing even after you quit your app

MPMusicPlayerController methods are quite self-explanatory:

- setQueueWithQuery: and - setQueueWithItemCollection are used to set playback queue with query (see below)

- play, - pause, - stop, - beginSeekingForward, - beginSeekingBackward, - endSeeking, - skipToNextItem, - skipToPreviousItem, - skipToBeginning are all used to control the player

currentPlaybackTime, nowPlayingItem, playbackState, repeatMode, shuffleMode, volume are all properties of the player that you can use to change the behavior or display different attributes

MPMediaItem MPMediaItem is a single item in the media library (such as one song). It is the nowPlayingItem property of the player. Each item has metadata associated with it, those can be accessed by calling valueForProperty: method. The full list of properties can be found in thedocumentation but some examples include MPMediaItemPropertyTitle or MPMediaItemPropertyArtist.

MPMediaQuery MPMediaQuery is used to do queries in the iPod library. Again, the full description is best to be found in the documentation but a little example demonstrates how MPMediaQuery works.

MPMediaQuery* query = [MPMediaQuery songsQuery]; [query addFilterPredicate:[MPMediaPropertyPredicate predicateWithValue:@"The Beatles" forProperty:MPMediaItemPropertyArtist comparisonType:MPMediaPredicateComparisonEqualTo]]; [query setGroupingType:MPMediaGroupingAlbum];

This creates a query that selects all songs whose artist is "The Beatles" and groups them by album. All the songs in the query can be passed to MPMusicPlayerController to play.

Example Now put it all together:

//Create an instance of MPMusicPlayerController MPMusicPlayerController* myPlayer = [MPMusicPlayerController iPodMusicPlayer]; //Create a query that will return all songs by The Beatles grouped by album MPMediaQuery* query = [MPMediaQuery songsQuery]; [query addFilterPredicate:[MPMediaPropertyPredicate predicateWithValue:@"The Beatles" forProperty:MPMediaItemPropertyArtist comparisonType:MPMediaPredicateComparisonEqualTo]]; [query setGroupingType:MPMediaGroupingAlbum]; //Pass the query to the player [myPlayer setQueueWithQuery:query]; //Start playing and set a label text to the name and image to the cover art of the song that is playing [myPlayer play]; someLabel.text = [myPlayer.nowPlayingItem valueForProperty:MPMediaItemPropertyTitle]; someImageView.image = [myPlayer.nowPlayingItem valueForProperty:MPMediaItemPropertyArtwork]; 

[touchthatfruit-blog]

Objective-C implementation of stacks and queues

Recently I run into a need of having a stack in my app and I found out that there is no such class in Cococa. I know that stacks and queues are easily replaced by NSMutableArray but I decided to wrap this functionality into a class to make it more elegant and easy to use. You can find the code on GitHub. Feel free to do whatever you want to do with it but I'd appreciate if you mentioned me. Or bought me a beer. How does this work is demonstrated on a simple example below.

//Stack - FILO (first in, last out) DKStack* stack = [[DKStack alloc] init]; [stack push:foo]; //Push foo on the stack [stack push:bar]; //Push bar on the stack [stack pop]; //Pop top element (bar) from the stack [stack top]; //Now returns foo [stack pop]; //Pop top element (foo) from the stack [stack isEmpty]; //Now returns YES //Queue - FIFO (first in, first out) DKQueue* queue = [[DKQueue alloc] init]; [queue push:foo]; //Push foo to the queue [queue push:bar]; //Push foo to the queue [queue pop]; //Pop first element (foo) from the queue [queue first]; //Now returns bar [queue pop]; //Pop bar from queue [queue isEmpty]; //Now returns YES  

[touchthatfruit-blog]

RawApps iPhone WordPress theme gets a redesign

Today I did a little redesign of RawApps WordPress theme for iPhone apps. I've removed all the pictures that were used to create background and looked, well... not so well. Now the background is just plain colour and the tabs for pages were replaced by a simple bar. Here it's what it looks like now (the bottom with widgets isn't shows, doesn't fit onto 13" screen).

I'll be working on adding a few more colour schemes to choose from and potentially even enabling custom colours. Should you have any comments on the design or what would you like to see in the future feel free to comment!

[touchthatfruit-blog]

Free WordPress theme for showcasing iPhone apps

As you may remember some time ago I discovered a great way of showcasing apps for any iPhone dev working on low budget - a free WordPress theme. Unfortunatelly there is only one of these available online from great guys at RawApps and it has not been updated for some time. After a few emails with them, they set up a GitHub repo to continue the development of the theme.

How to set this up First you will need WordPress downloaded and installed on your server. To do this follow the steps provided by WordPress, it shouldn't be hard. Once you download the theme, you need to copy it into /wp-content/themes directory and enable it in your WP admin panel under Settings->Themes. Set up the name, price, pictures and... you're done, enjoy! A nice website for your app is up and running.

Want to participate? As you may have noted this theme is not yet up-to-date and does need some improvements. If you'd like to participate in the development, you're strongly encouraged to do so and your time and effort will be highly appreciated by fellow devs. To do this just fork it on GitHub and use pull requests to submit changes.

[touchthatfruit-blog]

Two simple tricks with CABasicAnimation that make your app look better

Today I was browsing through my snippets in CodeBox (by the way - great app for anybody who works with code, saves a lot of time and work, get it here) and I came accross two simple snippets for animating objects using CABasicAnimation that can enhance an app in a great way if used right so I thought I'll share with you.

To begin with you need to add QuartzCore framework to your project. First snippet is animation that moves an element (UIView, UIWhatever...) along the x or y axis and it goes like this.

//Create a CABasicAnimation object CABasicAnimation *move = [CABasicAnimation animationWithKeyPath:@"transform.translation.y" ]; [move setFromValue:[NSNumber numberWithFloat:0.0f]]; [move setToValue:[NSNumber numberWithFloat:100.0f]]; [move setDuration:0.3f]; //Add animation to a specific element's layer. Must be called after the element is displayed. [[element layer] addAnimation:move forKey:@"transform.translation.y"];

Second snippet is a fade transition for whatever UI element.

//Create a CABasicAnimation object. Must be added to the element after it is displayed CATransition *animation = [CATransition animation]; animation.duration = 1.0; animation.type = kCATransitionFade; animation.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut]; [myLabel.layer addAnimation:animation forKey:@"changeTextTransition"]; // Change the text and the animation will ocur myLabel.text = @"Changed text";

There are couple of other options but honestly, do you need to rotate anything in your app? Adding those two kinds of animations makes your app feel much better and provide subtle feedback to the user. But always remeber that even for animation "less is more" is true and too much animation will ruin everything.

[touchthatfruit-blog]

iOS Bluetooth development tutorial - using GameKit to connect two iPhones

After working with Bluetooth using GameKit framework for a while in my current project I decided to write a basic tutorial that should help anybody to get started with connecting two iOS devices together. First let's talk about why and when should you use Bluetooth. When I came up with the idea of an app that requires two devices to communicate I had to make a choice of technology that will connect the devices. First thing that came to my mind was to use the Bump API. Why? Because the bumping idea is actually pretty cool + everything is set up for you and you can send data between two devices in just a couple lines of code. But wait - how did you say Bump works? Over the internet? Right... and what if the user does not have any connection? That's when your app becomes completely useless. So why not use GameKit API instead? I know the name suggests that it has been made for games but what stops you from using it for anything else? Everything is set up for you and you can send data between two devices in a few lines of code as well. Let's take a look how.

First you need to import the GameKit framework to your project. In XCode 4 you need to go to you target Build Phases tab and add GameKit.framework to the Link with Binary Libraries list. Then you need to set up a GKSessionDelegate. You need to carefully decide which of your classes is gonna be the delegate because if you pick the wrong one you end up having to rewrite large parts of your code as I did. The basic question is - when do you need to send and receive data. If it is just a one-off occasion you can set a certain view controller as the delegate but if you need the iPhones to stay connected all the time and the user navigates between multiple views it's probably the best idea to set your ApplicationDelegate as GKSessionDelegate and GKPeerPickerControllerDelegate.

A good tip if your're doing this is to make a macro that allows you to access the ApplicationDelegate from anywhere in your code. Obviously don't forget you have to #import the header file anywhere you need to use this. With this you can access any property of the delegate just by UIAppDelegate.anyProperty and you don't have to write the lengthy piece of code every time.

#define UIAppDelegate ((HelloWorldAppDelegate *)[UIApplication sharedApplication].delegate)

So first thing - the class we will use needs to conform to two protocols as shown below - GKSessionDelegate for handling the session and GKPeerPickerControllerDelegate for estabilishing the connection. Also it is a good idea to set up three properties as show below.

@interface HelloWorldAppDelegate : NSObject <UIApplicationDelegate, GKSessionDelegate, GKPeerPickerControllerDelegate> {     GKPeerPickerController *connectionPicker;     GKSession* connectionSession;     NSMutableArray *connectionPeers; } @property (retain) GKSession* connectionSession; @property (nonatomic, retain) NSMutableArray *connectionPeers; @property (nonatomic, retain) GKPeerPickerController* connectionPicker;

Then we need to properly initialize all those so add this somewhere to your code (didFinishLaunching or viewDidLoad).

connectionPicker = [[GKPeerPickerController alloc] init]; connectionPicker.delegate = self; //NOTE - GKPeerPickerConnectionTypeNearby is for Bluetooth connection, you can do the same thing over Wi-Fi with different type of connection connectionPicker.connectionTypesMask = GKPeerPickerConnectionTypeNearby; connectionPeers = [[NSMutableArray alloc] init];

Now we need to add methods that are needed to conform to the GKPeerPickerControllerDelegate. There is nothing much to do there, you can just copy them and change the session ID to ID your app will use.

#pragma mark - GKPeerPickerControllerDelegate - (GKSession *)peerPickerController:(GKPeerPickerController *)picker sessionForConnectionType:(GKPeerPickerConnectionType)type {     // Create a session with a unique session ID - displayName:nil = Takes the iPhone Name     GKSession* session = [[GKSession alloc] initWithSessionID:@"com.myapp.connect" displayName:nil sessionMode:GKSessionModePeer];     return [session autorelease]; } // Tells us that the peer was connected - (void)peerPickerController:(GKPeerPickerController *)picker didConnectPeer:(NSString *)peerID toSession:(GKSession *)session {     // Get the session and assign it locally     self.connectionSession = session;     session.delegate = self;         [picker dismiss]; }

And now comes the most important part - GKSessionDelegate. The principle for sending data is to convert them into NSData. If you are really sure you will need to send just, say, one NSString than you can encode it directly and just send it. But if you need to send anything more complicated I strongly recommend using the technique with an array and NSKeyedArchiver because it leaves plenty of space for later changes and allows you to send different chunks of data. As you will see this is even probably the easiest method for distinguishing what you actually received - you always get encoded array and when you recreate the array you can test whatever elements in it. Note that you could also use NSDictionary if you need to. And don't forget that if you send some custom classes they need to conform to the NSCoding protocol!

//Method for sending data that can be used anywhere in your app - (void)sendData:(NSArray*)data {     NSData* encodedArray = [NSKeyedArchiver archivedDataWithRootObject:data];     [UIAppDelegate.connectionSession sendDataToAllPeers:encodedArray withDataMode:GKSendDataReliable error:nil];                 [encodedArray release];            }

And now the method for receiving data.

#pragma mark - GKSessionDelegate // Function to receive data when sent from peer - (void)receiveData:(NSData *)data fromPeer:(NSString *)peer inSession: (GKSession *)session context:(void *)context {     NSArray *receivedData = [NSKeyedUnarchiver unarchiveObjectWithData:data];     //Handle the data received in the array     [receivedData release]; }

- (void)session:(GKSession *)session peer:(NSString *)peerID didChangeState:(GKPeerConnectionState)state {     if (state == GKPeerStateConnected) {         // Add the peer to the Array         [connectionPeers addObject:peerID];                 // Used to acknowledge that we will be sending data         [session setDataReceiveHandler:self withContext:nil];                 //In case you need to do something else when a peer connects, do it here     }     else if (state == GKPeerStateDisconnected) {         [self.connectionPeers removeObject:peerID];         //Any processing when a peer disconnects     } }

And finally two methods to call when you want to connect or disconnect usable from anywhere in your app.

- (void)connectToPeers:(id)sender {     [UIAppDelegate.connectionPicker show]; } - (void)disconnect:(id)sender {     [UIAppDelegate.connectionSession disconnectFromAllPeers];     [UIAppDelegate.connectionPeers removeAllObjects]; }

With this tutorial you should be able to set up basic Bluetooth communication between two iOS devices. Obviously there is a lot more in the documentation, take this just as basics that I have learnt somewhere else and slightly refined them.

[touchthatfruit-blog]

UIColor from RGB value

This is just a small but incredibly useful snippet - it returns you an instance of UIColor from given RGB value. Invaluable when you're matching your UI elements with your Photoshop graphics or anytime you know need UIColor from RGB. #define UIColorFromRGB(rgbValue) [UIColor                 colorWithRed:(((float)((rgbValue & 0xFF0000) >> 16))/255.0)                 green:(((float)((rgbValue & 0xFF00) >> 8))/255.0)                 blue:(((float)(rgbValue & 0xFF))/255.0) alpha:1.0] Put this code just under the #import bit and then use it like this UIColor *color = UIColorFromRGB(0x800080);

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Custom UISlider

Want to create a nice custom UISlider? There is a really simple way. Just use this bit of code in your viewDidLoad method or wherever you initialize the slider. UISlider *slider = [[UISlider alloc] init]; UIImage *sliderLeftTrackImage = [[UIImage imageNamed: @"slider_body_min.png"] stretchableImageWithLeftCapWidth: 9 topCapHeight: 0]; UIImage *sliderRightTrackImage = [[UIImage imageNamed: @"slider_body_max.png"] stretchableImageWithLeftCapWidth: 9 topCapHeight: 0]; UIImage *sliderThumb = [[UIImage imageNamed: @"slider_thumb.png"] stretchableImageWithLeftCapWidth: 9 topCapHeight: 0]; [slider setMinimumTrackImage: sliderLeftTrackImage forState: UIControlStateNormal]; [slider setMaximumTrackImage: sliderRightTrackImage forState: UIControlStateNormal]; [slider setThumbImage:sliderThumb forState:UIControlStateNormal]; // Now place you slider in a view and do anything else you want All you need to do is you need to draw three images - min and max bar for the track and the thumb. And that's it!

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UITableView shadows

Following the previous post about UINavigationBar shadow now I show how to do nice UITableView top and bottom shadows. It can be easily done in quite the same fashion - we create two UIViews as our shadows and just use them as header and footer views of our UITableView. Use this bit of code in viewDidLoad method of your UITableView. //Footer shadow UIView *footerShadow = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 320, 10)]; CGColorRef darkColor = [[UIColor blackColor] colorWithAlphaComponent:.5f].CGColor; CGColorRef lightColor = [UIColor clearColor].CGColor; CAGradientLayer *bottomShadow = [[[CAGradientLayer alloc] init] autorelease]; bottomShadow.frame = CGRectMake(0,0, self.view.frame.size.width, 10); bottomShadow.colors = [NSArray arrayWithObjects:(id)darkColor, (id)lightColor, nil]; footerShadow.alpha = 0.6; [footerShadow.layer addSublayer:bottomShadow]; self.tableView.tableFooterView = footerShadow; self.tableView.contentInset = UIEdgeInsetsMake(-10, 0, 15, 0); //Header shadow UIView *headerShadow = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 320, 10)]; CAGradientLayer *topShadow = [[[CAGradientLayer alloc] init] autorelease]; topShadow.frame = CGRectMake(0, 0, self.view.frame.size.width, 10); topShadow.colors = [NSArray arrayWithObjects:(id)lightColor, (id)darkColor, nil]; headerShadow.alpha = 0.3; [headerShadow.layer addSublayer:topShadow]; self.tableView.tableHeaderView = headerShadow; This works only for plain style UITableViews, not for the grouped ones. Also, if you are already using header and footer views for something else you can try it this way //relpace self.tableView.tableHeaderView = headerShadow; //with [self.tableView insertSubview:headerShadow aboveSubview:self.tableView.tableHeaderView]; //and self.tableView.tableFooterView = footerShadow; //with [self.tableView insertSubview:footerShadow belowSubview:self.tableView.tableFooterView];

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UINavigationBar shadow

Always wanted to add the cool shadow to your UINavigationBar? It can be simply done by creating a category of UINavigationController. Just add this code snippet to you ApplicationDelegate.m right before the implementation starts (or create a separate file for the category). All it does is that it draws the shadow using CALayer class. IMPORTANT: You also need to #import and add Quartz framework to your project for this to work. @interface UINavigationController (MyCustomNavController) @end @implementation UINavigationController (MyCustomNavController) - (void)viewWillAppear:(BOOL)animated {      CGColorRef darkColor = [[UIColor blackColor] colorWithAlphaComponent:.5f].CGColor;      CGColorRef lightColor = [UIColor clearColor].CGColor;      CGFloat navigationBarBottom;      navigationBarBottom = self.navigationBar.frame.origin.y + self.navigationBar.frame.size.height;      CAGradientLayer *newShadow = [[[CAGradientLayer alloc] init] autorelease];      newShadow.frame = CGRectMake(0,navigationBarBottom, self.view.frame.size.width, 10);      newShadow.colors = [NSArray arrayWithObjects:(id)darkColor, (id)lightColor, nil];      [self.view.layer addSublayer:newShadow];      [super viewWillAppear:animated]; } @end Note that you can also do this by subclassing UINavigationController, all you need to do is to override the - (void)viewWillAppear:(BOOL)animated in the same fashion the snipped does.

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Custom fonts in iOS app

Today I will write a simple tutorial explaining how to add custom fonts to you application enabling you to use them. First, you will need a font you will want to add. I guess this has to be a Truetype font (*.ttf) and I haven't tried anything else so maybe I'm wrong. But most fonts you can find online are Truetype anyway.

First thing you need to do is to add your font to you application the same way you would add anything else like pictures. Just drop it into your XCode project and add it. Then the important part comes - you need to tell your application to include them. You need to add this to your .plist file which you can find in Supporting files folder.

    <key>UIAppFonts</key>     <array>         <string>SueEllenFrancisco.ttf</string>         <string>JustMeAgainDownHere.ttf</string>         <string>WalterTurncoat.ttf</string>     </array>

Obviously you need to change the file names to file names of your font file(s) you added to your project previously. If you want to use your font in an application you need to create a font object which you assign to a font parameter of whatever you want. For example

myLabel.font = [UIFont fontWithName:[font fontName] size:size]; //or [myLabel setFont:[UIFont fontWithName:[font fontName] size:size]];

Be careful with the font names because they can differ from the file name so maybe have a look in your FontBook in case you installed the font on your computer as well. For me getting rid of the spaces worked so you might need things like @"SueEllenFrancisco".

To finish with there are two website which I use when I need a font - DaFont.com and Google Fonts.

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dequeueReusableCellWithIdentifier messing up custom cells solution

This problem actually took me quite a while to fix. It is basiclally this. When you have a longer UITableView with custom cells and you scroll, the cell elements get randomly duplicated. It is because the cells have all the same identifier and dequeueReusableCellWithIdentifier was using them in wrong places. In the end I found several solutions but the best one is to actually set a unique identifier for each cell.

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {        NSString *CellIdentifier = [NSString stringWithFormat:@"Cell %d, %d", indexPath.row, indexPath.section]; //this is where each cell gets uniquie identifier which prevents any problems             UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];     if (cell == nil) {         cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease];     }     // setup your custom cell...    return cell; }

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Duplicating UI elements in UITableView - solution

Today I ran into a strange problem. In settings tab in my app I have several UISwitches, UISlider and so on. The problem was that when I moved the slider, switched to another tab and back again and then I moved the slider there was another slider appearing under it. You could create an infinite number of sliders like this although only the topmost one was usable.

Finally I discovered what was the problem. In my viewWillAppear I called [tableView reloadData] method so every time the settings appeared the elements got created again in the usual place in (UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath.

This can be easily fixed by making all your UI elements nil in viewDidLoad and then putting it into condition while creating a new one.

//Make a UISlider property @interface SettingsTableView : UITableViewController <UIPickerViewDelegate, UIPickerViewDataSource> {     UISlider *fontSlider; } @property (nonatomic, retain) UISlider *fontSlider; @end @implementation SettingsTableView @synthesize fontSlider; -(void) viewDidLoad { ...     self.fontSlider = nil; //Set the slider to nil ...            [super viewDidLoad]; } //Create a new slider and add it to a cell only the first time - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {     static NSString *CellIdentifier = @"Cell";         UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];     if (cell == nil) {         cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease];     }             if (self.randomSwitch == nil)         {                [[cell textLabel]setText:@"A slider"];                self.fontSlider = [[[UISlider alloc] init] autorelease];                self.fontSlider.frame = CGRectMake(190, 9, 94 ,27);                [cell.contentView addSubview:self.fontSlider];          } }

And now you can call [tableView reloadData] without any side effects.

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Multiple UIBarButtonItems in UINavigationBar

Today I ran into a problem. In my app I need to have an UITableView that is accessed from another UITableView using UINavigationBar. Therefore, when you're in the second TableView, the right NavigationBar item is that button that allows you to go back to the first TableView. But I need to have at the "+" (add) button and "Edit" button for this TableView as well. So what? Luckily I found I way how to do it.

You need to create a new instance of a UIToolBar and fill it with buttons you need, that add them to your UINavigationBar. However, always remember that this does not look nice at all! UINavigationBar is not designed to do this but if you are in a situation like me and you really just need to have two buttons on one side of a NavigationBar here is a snippet that should help you.

    // Create the toobar     UIToolbar* toolbar = [[UIToolbar alloc]                           initWithFrame:CGRectMake(0, 0, 100, 45)];     [toolbar setBarStyle: UIBarStyleDefault];      // Create and array for the buttons     NSMutableArray* buttons = [[NSMutableArray alloc] initWithCapacity:3];     // Create a "+" button     UIBarButtonItem *addButton = [[UIBarButtonItem alloc]                                    initWithBarButtonSystemItem:UIBarButtonSystemItemAdd                                    target:self                                    action:@selector(addAction:)];     addButton.style = UIBarButtonItemStyleBordered;     [buttons addObject:addButton];     [addButton release];     // Create a spacer between them     UIBarButtonItem *spacer = [[UIBarButtonItem alloc]                                initWithBarButtonSystemItem:UIBarButtonSystemItemFixedSpace                                target:nil                                action:nil];     [buttons addObject:spacer];     [spacer release];     // Create an "Edit" button     UIBarButtonItem *editButton = [[UIBarButtonItem alloc]                                      initWithBarButtonSystemItem:UIBarButtonSystemItemEdit                                      target:self                                      action:@selector(editAction:)];     editButton.style = UIBarButtonItemStyleBordered;     [buttons addObject:editButton];     [editButton release];     // Add the buttons to the toolbar and release them     [toolbar setItems:buttons animated:NO];     [buttons release];       // Add the toolbar to the NavigationBar     self.navigationItem.rightBarButtonItem = [[UIBarButtonItem alloc]                                      initWithCustomView:toolbar];     [toolbar release];

Here is a screenshot of the result.

Hope it helps!

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viewWillAppear and viewDidAppear not being called in your UINavigationController or UITabBarController - SOLUTION

Yesterday I ran into a problem. I had a UITableView shown via NavigationController in one of my tabs in TabBarController. It took me quite a while of googling to come up with a solution for this so I bring it to you.

First you need to setup your root view as a UINavigationControllerDelegate.

@interface RootViewController : UIViewController <UINavigationControllerDelegate> {     IBOutlet UINavigationController* navigationController; } @property (nonatomic, retain) UINavigationController* navigationController; @end

Somewhere in the implementation then (I do it in the viewDidLoad method) assign RootViewController as a delegate of navigationController

- (void)viewDidLoad {     navigationController.delegate = self;     [super viewDidLoad]; }

Finally you need to add two methods to your RootViewController so it conforms to the UINavigationControllerDelegate protocol. This will secure that viewWillAppear and viewDiDAppear gets called every time you switch views with your NavigationController

- (void)navigationController:(UINavigationController *)navigationController       willShowViewController:(UIViewController *)viewController animated:(BOOL)animated {     [viewController viewWillAppear:animated]; } - (void)navigationController:(UINavigationController *)navigationController        didShowViewController:(UIViewController *)viewController animated:(BOOL)animated {     [viewController viewDidAppear:animated]; }

What took me more time to figure out is when you have UITabBarController a run into a similar problem. The solution is technically the same as for NavigationController. You need to have a <UITabBarControllerDelegate>, usually it would be your ApplicationDelegate. Then you simply need to add a method to this delegate which will secure that everytime you switch tabs the appropriate message is sent to the View that appears.

- (void)tabBarController:(UITabBarController *)tabBarController didSelectViewController:(UIViewController *)viewController {     [viewController viewWillAppear:NO]; }

Obviously you need to set the class as a delegate of the tabBarController somewhere, so you need something like this (you don't have to assign it in didFinishLaunchingWithOptions if your tabBarController delegate is something else then you application delegate):

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {        self.tabBarController.delegate = self;       [self.window addSubview:tabBarController.view];     [self.window makeKeyAndVisible];     return YES; }

And the final part, what to do if you have a NavigationController in a tab of TabBarController? Surprisingly you need to follow what I have done above and then you need to add two simple methods to you RootViewControler like this:

- (void)viewWillAppear:(BOOL)animated {     [navigationController viewWillAppear:animated]; } - (void)viewDidAppear:(BOOL)animated {     [navigationController viewDidAppear:animated]; }

It secures that message will be sent to your navigationController whenever RootViewController (the one in the tab) is switched to. NavigationController then passes the message to whatever view is on top and makes it fire viewWillAppear or viewDidAppear method.

I hope you found this useful if you found yourself struggling with viewDid/WillAppear methods not getting called in your views in your NavigationController or TabBarController.