Let’s start with a quick look at how this appears to the user. Assume the application TestApp is running in the foreground. When the application is put into the background by pressing the home button, within 1 second (see the code below), the following local notifications will appear (iOS 5 and iOS 4):

If the user taps on the message, the application return to the foreground.

The code is quite simple, it begins with creating an NSDate object with the current date/time, adding one second to that time, and setting the fire date for a local notification to the configured date. From there, setup the local notification messaging and wrap up by scheduling the notification with the OS.

- (void)applicationDidEnterBackground:(UIApplication *)application
{
  UILocalNotification *localNotification = [[[UILocalNotification alloc] init] autorelease];
 
  // Current date
  NSDate *date = [NSDate date]; 
 
  // Add one second to the current time
  NSDate *dateToFire = [date dateByAddingTimeInterval:1];
 
  // Set the fire date/time
  [localNotification setFireDate:dateToFire];
  [localNotification setTimeZone:[NSTimeZone defaultTimeZone]];    
 
  // Setup alert notification
  [localNotification setAlertBody:@"Tap to return to TestApp" ];
  [localNotification setAlertAction:@"Open TestApp"];
  [localNotification setHasAction:YES];
 
  [[UIApplication sharedApplication] scheduleLocalNotification:localNotification];
}

Once the notification has been presented to the user, and the user acknowledges, the method below in your application will be called once the app comes to the foreground:

- (void)application:(UIApplication *)application didReceiveLocalNotification:(UILocalNotification *)notification
{
  // Your code here...
}

Again, consider this option as a reminder to the user only in cases where an important process was underway, not as the default operation when the app goes into the background.

In Objective-C, all objects (derived from NSObject) have a description method, which returns an NSString describing the object. When using GDB, you can print the description using print-object, for example, let’s use the interface definition below to look at a few descriptions:

@interface SandboxViewController : UIViewController <UITextFieldDelegate>
{
  UITextField  *username;
  UIButton     *testButton;
  UILabel      *label;
  UIView       *view;
}

When stopped on a breakpoint in the SandboxViewController object, GDB can display information on each object:

Note, po is equivalent to print-object.

Print-Object and recursiveDescription

When working with UIView objects, there is an additional method for obtaining information, recursiveDescription. When using print-object and calling this method you can see the entire view hierarchy for the object.

With the SandboxViewController object defined above, in the loadView method I created a UIView as follows:

[self setView:[[[UIView alloc] initWithFrame:[[UIScreen mainScreen] applicationFrame]] autorelease]];

Within GDB, when on a breakpoint within the SandboxViewController object, I can now view the entire view hierarchy as follows:

The same idea works for a UIView that is not associated with a view controller. Using the view defined below, and the label added as a subview:

// Create UIView
view = [[UIView alloc] initWithFrame: CGRectMake(10, 10, 300, 50)];
[[self view] addSubview:view];
 
// Add label to UIView
UILabel *tmplabel = [[UILabel alloc] initWithFrame:CGRectMake(10, 20, 280, 80)];    
[tmplabel setTextColor:[UIColor whiteColor]];
[tmplabel setTextAlignment:UITextAlignmentLeft];
[tmplabel setText: @"Enter your password:"];
[view addSubview:tmplabel];

Here is the recursive description:

With Xcode 4 the process for setting NSZombieEnabled is different than in earlier versions of Xcode. To configure zombies, enter ⌥-⌘-r (alt-command-r). Once the dialog is shown, choose the option Enable Zombie Objects

When using a zombie, any message sent to an object that has already released will result in an exception being thrown, which will look similar to the screenshot below:

The first approach I took was to loop through all the files, building a path to each, one by one:

// Path to the Documents directory
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
if ([paths count] > 0)
{
  NSError *error = nil;  
  NSFileManager *fileManager = [NSFileManager defaultManager];
 
  // Print out the path to verify we are in the right place
  NSString *directory = [paths objectAtIndex:0];
  NSLog(@"Directory: %@", directory);
 
  // For each file in the directory, create full path and delete the file
  for (NSString *file in [fileManager contentsOfDirectoryAtPath:directory error:&error])
  {    
    NSString *filePath = [directory stringByAppendingPathComponent:file];
    NSLog(@"File : %@", filePath);
 
    BOOL fileDeleted = [fileManager removeItemAtPath:filePath error:&error];
 
    if (fileDeleted != YES || error != nil)
    {
      // Deal with the error...
    }
  }
 
}

The code above works fine, however, I was interested in something that didn’t build each path separately – the code below deletes all the files in one fell swoop:

 
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
if ([paths count] > 0)
{
  NSLog(@"Path: %@", [paths objectAtIndex:0]);
 
  NSError *error = nil;  
  NSFileManager *fileManager = [NSFileManager defaultManager];
 
  // Remove Documents directory and all the files
  BOOL deleted = [fileManager removeItemAtPath:[paths objectAtIndex:0] error:&error];
 
  if (deleted != YES || error != nil)
  {
    // Deal with the error...
  }
 
}

Given the requested item to remove was a directory, as you’d expect, not only were the files deleted, so was the Documents directory. Problem is, I ran into errors when I attempted to drag/drop new files into the file sharing areas iTunes.

To get things working again, I changed up the code above to create the Documents directory:

NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
if ([paths count] > 0)
{
  NSLog(@"Path: %@", [paths objectAtIndex:0]);
 
  NSError *error = nil;  
  NSFileManager *fileManager = [NSFileManager defaultManager];
 
  // Remove all files in the documents directory
  BOOL deleted = [fileManager removeItemAtPath:[paths objectAtIndex:0] error:&error];
 
  if (deleted != YES || error != nil)
  {
    // Deal with the error...
  }
  else
    // Recreate the Documents directory
    [fileManager createDirectoryAtPath:[paths objectAtIndex:0] withIntermediateDirectories:NO attributes:nil error:&error];
 
}

Although there is less code to delete the Documents directory, something tells me it may simply be a better (and more robust) solution to loop and delete each file in sequence.

There is an abundance of interesting code in the project, including numerous block animations. Many of the little things Sam has already dialed in – for example, the size of an HUD is dynamically adjusted when displaying text, the longer the text, the wider the view (and support for wrapping text works out of the box).

Below are a few screenshots, the first shows a long message that is wrapped to fit the display:

The images below show two of the options for dismissing messages, one for successful operations, one for error conditions:

Download SVProgressHUD

You can download SVProgressHUD from github.

Open Source Recommendations ?

Have you written or worked with iOS or Cocoa open source that you think others would find interesting, send me a note.

The first thing to understand is that commands can only be entered into GDB when the debugging process is stopped, which is done via breakpoints. If you hit a breakpoint, the debug console will look as follows:

Notice the (gdb) prompt, politely waiting your input. No better place to start than requesting help information. While in the debug console (and on a breakpoint), from the GDB prompt, type in “help”

Once the high-level help categories are shown, you can look further by viewing one of the classes of commands. For example, below is a list of all the commands for examing data:

GDB Print Command

From the help info shown above, let’s look at the print command:

The expression (EXP) to be printed can be as simple as showing the current value of a variable – for example, using the code below, here’s how to print the value of the variable ‘counter’

#define MAX_CLICK  5
 
- (void)someMethod:(int)counter title:(NSString *)title message:(NSString *)msg
{
  if (counter++ > MAX_CLICK)
  {
    UIAlertView* alertView = [[UIAlertView alloc] initWithTitle:title 
      message:msg delegate:self cancelButtonTitle:@"Ok" otherButtonTitles:nil];
    [alertView show];
  }
}

Each time the method above stops on breakpoint at the if statement, the value of counter can be viewed:

Notice the shortcut for print (p) command is used above in the second command.

You can also use expressions when working with variables. Understand the examples that follow are a bit contrived, however, for the sake of illustration please bear with me. Notice that depending on how use define an expression, the value of the expression will vary:

GDB Print-Object Command

Looking at the help information for the data commands, notice there is also a print-object command, which will call the description method of an Objective-C object. Let’s assume we call someMethod (which is listed above), using the following call:

[self someMethod:x++ title:@"Error Message" message:@"Max Counter Value Reached."];

If we were to set a breakpoint at the line if (counter++ > MAX_CLICK), we could view the objects title and msg:

Notice the shortcut for print object (po) is used in the second example above.

Print-object is very helpful when looking at objects that are collections, for example NSDictionary and NSArray objects. We can view the following dictionary object using the print-object command:

NSArray *arrayOfDictionaryObjects = [NSArray arrayWithObjects:
      [NSDictionary dictionaryWithObjectsAndKeys:@"1234", @"accountID", [NSNumber numberWithBool:YES],  @"isActive", nil],
      [NSDictionary dictionaryWithObjectsAndKeys:@"2345", @"accountID", [NSNumber numberWithBool:NO],  @"isActive", nil],
      [NSDictionary dictionaryWithObjectsAndKeys:@"3456", @"accountID", [NSNumber numberWithBool:YES], @"isActive", nil],
      [NSDictionary dictionaryWithObjectsAndKeys:@"4567", @"accountID", [NSNumber numberWithBool:NO],  @"isActive", nil], nil];

At this point, even with this cursory introduction to GDB, hopefully you have a basic idea of the power of GDB. In future posts I dive further into GDB and show you how to make the most of debugging from the command interface.

The images below show the basic idea, however, you owe it to yourself to download and run the demo project to get the full effect.

And the best part of integrating the transition into your project, the code is as simple as shown below:

MFDoorwayTransition *transition = [[MFDoorwayTransition alloc] 
   initWithBaseView:self.view
   firstView:self.currentView 
   lastView:self.nextView];
[transition buildAnimation];
[transition release];

Download Doorway Transition

You can download DoorwayTransition from github.

Open Source Recommendations ?

Have you written or worked with iOS or Cocoa open source that you think others would find interesting, send me a note.

Change UINavigationBar Background

With the release of iOS 5, the UIAppearance protocol is used to access the appearance proxy for a class you would like to configure. Customization is done by sending messages to the target class appearance proxy. When changing the appearance of an object, all instances of the object can be updated or only specific instances within a container class.

Let’s see how this looks as it relates to updating the background color of a UINavigationBar, it’s text and the back button which will allow a user to return to a previous view controller.

The image below is the gradient that I will use for the background:

Using the above image, I created a one pixel wide image for both portrait and landscape variations of the navbar, reason being, the height of the navar bar when the device is in portrait mode is 44, whereas the height for landscape is 32.

The images in my project are NavigationPortraitBackground.png and NavigationLandscapeBackground.png, both shown below:

I now create two UIImage objects:

// Create image for navigation background - portrait
UIImage *NavigationPortraitBackground = [[UIImage imageNamed:@"NavigationPortraitBackground"] 
                              resizableImageWithCapInsets:UIEdgeInsetsMake(0, 0, 0, 0)];
 
// Create image for navigation background - landscape
UIImage *NavigationLandscapeBackground = [[UIImage imageNamed:@"NavigationLandscapeBackground"] 
                              resizableImageWithCapInsets:UIEdgeInsetsMake(0, 0, 0, 0)];

To set these images as the new backgrounds for all navigation bars, here’s all I need to do:

// Set the background image all UINavigationBars
[[UINavigationBar appearance] setBackgroundImage:NavigationPortraitBackground 
                                     forBarMetrics:UIBarMetricsDefault];
[[UINavigationBar appearance] setBackgroundImage:NavigationLandscapeBackground 
                                     forBarMetrics:UIBarMetricsLandscapePhone];

In addition to the color, I can change the appearance of the text on all navigations bars as well:

// Set the text appearance for navbar
[[UINavigationBar appearance] setTitleTextAttributes:
    [NSDictionary dictionaryWithObjectsAndKeys:
    [UIColor whiteColor], UITextAttributeTextColor, 
    [UIColor redColor], UITextAttributeTextShadowColor, 
    [NSValue valueWithUIOffset:UIOffsetMake(0, 0)], UITextAttributeTextShadowOffset, 
    [UIFont fontWithName:@"Verdana-Bold" size:16], UITextAttributeFont, 
    nil]];

As the final step, I will update the back button with a custom image, which is shown below (the button is shown on a gray backdrop so you can see the white border):

Using what I described in the early post about cap insets, I can create a UIImage object and use the appearance API of the UIBarButtonItem to set the back button look. Notice that each value in the cap inset is set to 12, indicating all four corners are to hold steady at 12 pixels, even if the images stretched or resized.

// Set back button for navbar
UIImage *backButton = [[UIImage imageNamed:@"blueButton"]  resizableImageWithCapInsets:UIEdgeInsetsMake(12, 12, 12, 12)];
  [[UIBarButtonItem appearance] setBackButtonBackgroundImage:backButton forState:UIControlStateNormal barMetrics:UIBarMetricsDefault];

The last step is to create a button for the user interface that will push a new view controller, which will update the navigation bar to show the custom back button created above.

...
 
testButton = [[UIButton alloc] initWithFrame:CGRectMake(80, 30, 160, 44)];  
[testButton setTitle:@"Test Button" forState:UIControlStateNormal];
 
// Notice cap insets are different from above
UIImage *buttonImage = [[UIImage imageNamed:@"blueButton"]  resizableImageWithCapInsets:UIEdgeInsetsMake(0, 16, 0, 16)];
 
[testButton addTarget:self action:@selector(buttonPressed:) forControlEvents: UIControlEventTouchUpInside];        
[testButton setBackgroundImage:buttonImage forState:UIControlStateNormal];
 
...

An important concept to understand here, I’ve used the same image, blueButton.png, for both the custom back button as well as the button on the primary user interface – setting the cap insets specifies the rules, if you will, of how the image can be stretched, yet keep the look appropriate for the context in which the button will appear (that is, on the navbar or main UI).

A few screenshots follow that show the custom navigation bar, text and buttons in both portrait and landscape modes:

Download the Xcode Project

You can download the entire project source code here.

To get a list of the system wide settings:

NSDictionary* defaults = [[NSUserDefaults standardUserDefaults] dictionaryRepresentation];
NSLog(@"Defaults: %@", defaults);

A partial list of the output on my device follows:

Defaults: {
    AppleICUForce24HourTime = 0;
    AppleITunesStoreItemKinds =     (
        wemix,
        podcast,
        ...
    );
    AppleKeyboards =     (
        "en_US@hw=US;sw=QWERTY",
        "zh_Hant-HWR@sw=HWR",
        "emoji@sw=Emoji"
    );
    AppleKeyboardsExpanded = 1;
    AppleLanguages =     (
        en,
        "zh-Hant",
        fr,
        de,
  ...
}

As you can tell, the defaults returned above are contained within a dictionary object. The list of keyboards in the dictionary is stored as an NSArray object. To retrieve the array, simply request the object for the key “AppleKeyboards”

NSArray *array = [[NSUserDefaults standardUserDefaults] objectForKey:@"AppleKeyboards"];
NSLog(@"Keyboards: %@", array);

The output of all the installed international keyboards looks as follows:

Keyboards: (
    "en_US@hw=US;sw=QWERTY",
    "zh_Hant-HWR@sw=HWR",
    "emoji@sw=Emoji"
)

As I got further into the customization of the buttons, I ran into a method within UIImage that was introduced in iOS 5, resizableImageWithCapInsets. I found myself getting side-tracked from the original idea of navbar look and feel, to understanding how cap insets work. This post delves into what I learned.

Cap Insets with UIButton

As the documentation describes, you use resizableImageWithCapInsets to add cap insets to an image, when the image is resized or scaled, cap areas are not affected. The best way to understand this is through an example.

Let’s assume I want all the buttons on my UI to have a similar look, a gradient with a white border. Below is the image used for the examples in this post (the button is shown on a gray backdrop so you can see the white border):

Depending on the context of where the button appears, its size may vary. The code to create a button with the image and the corresponding output follow:

UIButton *button = [[UIButton alloc] initWithFrame:CGRectMake(80, 130, 160, 44)];  
[button setTitle:@"Test Button" forState:UIControlStateNormal];
 
// Image with without cap insets
UIImage *buttonImage = [UIImage imageNamed:@"blueButton"];
 
[button addTarget:self action:@selector(buttonPressed:) forControlEvents: UIControlEventTouchUpInside];        
[button setBackgroundImage:buttonImage forState:UIControlStateNormal];
[[self view] addSubview:button];

As you can see, the button is stretched in all directions. Let’s change the code to include cap insets, however, before we do that, let’s look at the signature of the cap insets method:

- (UIImage *)resizableImageWithCapInsets:(UIEdgeInsets)capInsets

Looking on step further, UIEdgeInserts is defined as:

typedef struct {
   CGFloat top, left, bottom, right;
} UIEdgeInsets;

UIEdgeInsets is structure that specifies float values for each cap inset: top, left, bottom and right areas of an image. To apply this to the image for the button, here is all we need to do:

// Image with cap insets
UIImage *buttonImage = [[UIImage imageNamed:@"blueButton"]  
   resizableImageWithCapInsets:UIEdgeInsetsMake(0, 16, 0, 16)];

This requests that the left and right 16 pixels of the original image are not scaled or resized when stretching the image to accomodate the button size frame defined above. The end results is as shown below:

Cap Insets with UIBarButtonItem

We can use the same image for a button on a navbar (I’ll show the specifics in the next post on customizing the navbar). Without specifying the cap insets, the button looks as follows:

The code below specifies an image where 12 pixels on the top, left, bottom and right be preserved when stretching/resizing the button:

UIImage *backButton = [[UIImage imageNamed:@"blueButton"]  
   resizableImageWithCapInsets:UIEdgeInsetsMake(12, 12, 12, 12)];

The output nows looks as follows:

Next Post

With that under our belt, in the next post I’ll continue with my original idea of customizing UINavigationBar, including background, title and text, as well as the buttons on the navbar.