Category Archives: iOS Development

How to determine the height of the keyboard in iOS

Keyboards in iOS can have various sizes. Not only can a keyboard be presented in portrait or landscape, on various devices with a plethora of screen sizes, and users may have QuickType enabled or disabled. Too many variables for hard coding.

Lucky for us, we can check all kinds of properties about a keyboard by dissecting the dictionary that is passed with the notifications mentioned in my previous post. If you recall, we can check when a keyboard appears or disappears using an observer. Let’s take a look at that notification when the keyboard is presented, and we can extract the height like this:

- (CGFloat)grabKeyboardHeight:(NSNotification *)notification {
    
    // grab keyboard size
    NSDictionary *userInfo = notification.userInfo;
    NSValue *keyFrame = [userInfo valueForKey:UIKeyboardFrameEndUserInfoKey];
    CGRect keyboardFrame = keyFrame.CGRectValue;
    CGFloat height = keyboardFrame.size.height;
    
    return height;
}

The keyboard’s width can be determined in much the same way. The dictionary holds many other interesting goodies, for example how long it takes iOS to animate it onto the screen:

- (NSTimeInterval)grabAnimationDuration:(NSNotification *)notification {
    
    // find out how long the keyboard animation lasts
    NSDictionary *userInfo = notification.userInfo;
    NSTimeInterval duration = [[userInfo valueForKey:UIKeyboardAnimationDurationUserInfoKey]doubleValue];
    
    return duration;
}

Apple has the full list if interesting objects for us to play with:





How to detect when the keyboard appears and disappears in iOS

To detect when the keyboard from a UITextField is being brought up (and goes away again), the UITextField Delegate Protocol won’t help us. Instead we need to listen to two notifications, namely UIKeyBoardWillShow and UIKeyboardWillHide.

We could setup the observers in viewDidLoad, like this for example:

- (void)viewDidLoad {
    [super viewDidLoad];
    
    // setup keyboard observers
    [[NSNotificationCenter defaultCenter]addObserver:self selector:@selector(keyboardCameUp:) name:UIKeyboardWillShowNotification object:nil];
    [[NSNotificationCenter defaultCenter]addObserver:self selector:@selector(keyboardWentAway:) name:UIKeyboardWillHideNotification object:nil];
}

These observers will call a method in our class (using @selector). Mine are called keyboardCameUp and keyboardWentAway:

- (void)keyboardCameUp:(NSNotification *)notification {
    
    NSLog(@"Keyboard came up!");
}

- (void)keyboardWentAway:(NSNotification *)notification {
    
    NSLog(@"Keyboard went away!");
}

The notification can be used to detect some properties of the keyboard, for example its height and width.





How to submit your apps to the App Store with Xcode 8

In case it’s been a while that you had to deal with App Store submissions, here’s a quick refresher. This assumes that iTunes Connect is ready to receive a new app or update.

Make sure that the version number and build values have both been increased if your submission is an update. In Xcode, do the following:

  • verify that the Archive Scheme is set to Release (under Product – Scheme – Edit Scheme)
  • make sure that you’ve selected “Generic iOS Device” as the active scheme
  • head over to Product – Archive to create an archive of your current version
  • the Organizer window opens, showing previously archived versions of your app (don’t delete those)
  • now hit Validate to see if there are any issues with your app
  • if all is well, hit the big blue Upload to App Store button
  • now pray that your app is approved





How to fix http load errors in your apps since iOS 10

In 2016, Apple have implemented a new rule that won’t let us load data from unsecured websites anymore. That’s those beginning with http:// instead of https:// (the latter ones are secured with an SSL certificate, and hence traffic is encrypted).

When you load an unsecured source, you’ll get an error message like this:

App Transport Security has blocked a cleartext HTTP (http://) resource load since it is insecure. Temporary exceptions can be configured via your app's Info.plist file.

If a secured source of the data is available, it’s probably the easiest method to change the feed. However, if that’s not an option, we can convince Xcode to let our apps download what’s known as data from “arbitrary” sources. Here’s how to do it.

First, in Xcode, navigate to your project’s target and find the Info tab. The target is the one that has your app icon showing, NOT the blue Xcode icon (top left, in the Project Navigator).

Now right-click on any of the many lines and select “Add Row”. This adds a value to your Info.plist file. Notice a list that comes up. Either select “App Transport Security” (if you can find it), or type NSAppTransportSecurity (it usually auto-completes). The entry will change into App Transport Security.

Let’s add the appropriate values to this new entry now. Hover over your new row now and select the little plus icon that comes up, then choose “Allow Arbitrary Loads” from the list. Alternatively, type in NSAllowsArbitraryLoads. Again this value will change to Allow Arbitrary Loads. Notice that this entry is a BOOL, and it needs to be set to YES on the right hand side. Go ahead and do that.

This will be enough to allow HTTP loads inside your app from any URL. You can restrict this to only certain URLs or hosts by adding another entry to the App Transport Security line, namely “Exception Domains”. Add each domain to its own line, and only data from those will be allowed to load via HTTP. If you want to use restricted domains, make sure to set the Allow Arbitrary Loads value to NO.





How to break a for loop in C and Objective-C

Did you know that we can break out of a for loop before it finishes? It’s true – and it works with both regular for loops, as well as fast enumeration (for…in loops). And we can do it in either of two ways.

Let’s imagine we have an array with one thousand words. We’re only interested in finding a single one, and at that point we want to stop the loop.

Breaking with the break statement

The break statement will get us out of a for loop and continue programme execution after the finishing bracket of the loop. Here’s an example with a regular for loop:

    for (int i=0; i<1000; i++) {

        NSString *word = [array objectAtIndex:i];
        if ([word isEqualToString:@"one"]) {

            // break the loop
            break;
        }
    }
    // execution continues here
    NSLog(@"We've broken from the loop.");

The break statement also works with fast enumeration:

    for (NSString *word in array) {

        if ([word isEqualToString:@"up"] || [word isEqualToString:@"the"]) {

            // break the loop
            break;
        }
    }

    // execution continues here
    NSLog(@"We've broken from the loop.");

Breaking with “goto label”

Goto sounds like an old BASIC command – and we can still use it in Objective C. It doesn’t work on its own though and needs an arbitrary label to which we can direct the loop after we’ve broken from it.

Here’s how we might do this with a regular for loop:

    for (int i=0; i<1000; i++) {

        NSString *word = [array objectAtIndex:i];

        if ([word isEqualToString:@"the"]) {

            // break the loop with a label
            goto myLabel;
        }
    }

    myLabel:;
    NSLog(@"We've broken from the loop.");

Notice that when we declare the label where we’d like the programme to continue, we must do so with a colon (and a semi colon to finish the line).

The same principle also works with fast enumeration:

    for (NSString *word in array) {

        if ([word isEqualToString:@"up"] || [word isEqualToString:@"the"]) {

            // break the loop
            goto outer;
        } 
    }

    myLabel:;
    NSLog(@"We've broken the loop.");




How to use a specific voice for text-to-speech in iOS

There are two ways of creating voices with which we can make iOS talk: creating a voice using a locale (classic), or creating a voice using a specific voice identifier (futuristic).

Let me show you both options here.

Classic and Easy

In this snipped we’re creating a voice with a certain dialect, British English in this case:

NSString *phrase = @"I'm listening.";

AVSpeechSynthesizer *synthesizer = [[AVSpeechSynthesizer alloc]init];

AVSpeechUtterance *utterance = [[AVSpeechUtterance alloc]initWithString:phrase];

AVSpeechSynthesisVoice *voice = [AVSpeechSynthesisVoice voiceWithLanguage:@"en-GB"];

utterance.voice = voice;

[synthesizer speakUtterance:utterance];

While very straightforward, we don’t know if the voice is going to be male or female. All we can specify is the language and dialect.

Futuristic and Specific

The above works fine and probably was enough when the speech synthesiser framework was introduced in iOS 7, but since then there are a myriad of other voices we can use in our applications. To specify one of them, we need a voice identifier.

Here’s how to do it:

NSString *phrase = @"I'm listening.";

AVSpeechSynthesizer *synthesizer = [[AVSpeechSynthesizer alloc]init];

AVSpeechUtterance *utterance = [[AVSpeechUtterance alloc]initWithString:phrase];

AVSpeechSynthesisVoice *voice = [AVSpeechSynthesisVoice voiceWithIdentifier:@"com.apple.ttsbundle.Karen-compact"];

utterance.voice = voice;

[synthesizer speakUtterance:utterance];

The setup is almost the same, but instead of the voiceWithLanguage method, we’re using the voiceWithIdentifier method here.

Finding Voices

To see a list of all available voices on the device, we can access the speechVoices method of the AVSpeechVoices class. This will return an array of AVSpeechVoices, all of which have a name, quality and identifier property. The latter is what we’re looking for so we can create a specific voice.

Here’s a method lists all available voices on the current device:

- (void)listVoices {

    NSArray *allVoices = [AVSpeechSynthesisVoice speechVoices];

    for (AVSpeechSynthesisVoice *voice in allVoices) {
        
        NSLog(@"Voice Name: %@, Identifier: %@, Quality: %ld", voice.name, voice.identifier, (long)voice.quality);

    }
}

Not all voices may be installed on all devices. For example, Alex is an optional high quality voice that the user needs to download first before he will show up in this array.

The quality parameter either returns 1 for standard/low-res, or 2 for enhanced/hi-res voices. Again it is up to the user to enable the hi-res quality of a voice under Settings.