In Part 1 of this series, I will introduce you to the very basics of CoreLocation services and getting the location of the device currently being used.

About CoreLocation

The CoreLocation framework provides your app with the ability to get a device’s current location, provided the user of the device has granted your app access to that information.

Location services are provided in two major ways using this framework:

1. Standard Location Services- This service provides the most accurate location information using a variety of methods including celluar, wifi, and GPS.
   • Most accurate.
   • Consumes the most power and can take a longer time to acquire.
   • Can only be used when your application is in the foreground.
2. Significant Change Location Services- This service uses cellular data to determine a general idea of where the device is located.
   • Fastest and uses the least amount of power to determine the location.
   • Can also be used to notify your app when a significant change in the location has occurred even if your app is not in focus.

Project Files:

You can download the project files at this github repository: http://github.com/shawngrimes/Location-and-Map-Sample

Adding Location Frameworks

The first step to adding location services to your project is to add the CoreLocation framework.

1. Select your target and go to the “Build Phases” tab.
2. Click the “+” button under “Link Binary With Libraries”
3. Select the CoreLocation framework and click “Add”

Location Manager

With location services, you create an instance of CLLocationManager. There is usually one instance of this per app so I feel a good place for this is in the App Delegate and then each view can access the current location from the App Delegate.

To start, open your App Delegate header file:

1. Add #import <CoreLocation/CoreLocation.h> to the top
2. Specify that your app delegate complies with the Core Location Delegate protocol by changing your @interface line with @interface CFAAppDelegate : UIResponder <UIApplicationDelegate, CLLocationManagerDelegate>
3. Specify a CLLocationManager property by adding @property (strong, nonatomic) CLLocationManager *locationManager right before the @end statement.

Your App Delegate header file should now look similar to the following:

#import <UIKit/UIKit.h>
 
//Add Location Framework
#import <CoreLocation/CoreLocation.h>
 
//Specify this app delegate complies with the location manager delegate
@interface CFAAppDelegate : UIResponder <UIApplicationDelegate, CLLocationManagerDelegate>
 
@property (strong, nonatomic) UIWindow *window;
 
//Add a location manager property to this app delegate
@property (strong, nonatomic) CLLocationManager *locationManager;
 
@end

Creating The Location Manager Object

Switch over to the App Delegate implementation file (.m), and we are going to create our location manager object. The first thing we should do, since we created it as a property of our app delegate, is synthesize the property so add @synthesize locationManager=_locationManager; under the line that reads @synthesize window = _window;.

#import "CFAAppDelegate.h"
 
@implementation CFAAppDelegate
 
@synthesize window = _window;
@synthesize locationManager=_locationManager;

Now that our property is synthesized, we can create the object. I usually create it in the method application didFinishLaunchingWithOptions:. A Location Manager object is created similar to any other object but there are three important properties you should set after you have alloc’d/init’d.

1. .purpose – The purpose property is displayed to the user of your app when they are prompted to allow your app to use their location. It gives you a chance to explain what your app is going to do with their location information.
2. .desiredAccuracy – The desired accuracy property allows you to tell the device how accurate you would like the location information to be. This should be set based on your application’s needs. Don’t set this property to kCLLocationAccuracyBest if you only need to know what city they are in. NOTE: This is the “desired” accuracy, it is not guaranteed. The device will determine the best available information and provide it to you but you are not, however, guaranteed any level of accuracy.
3. .distanceFilter – The distance filter property tells the location manager how far a device needs to move (horizontally vs. an altitude change) before triggering a new location event. It is measured in meters. You can set the property to kCLDistanceFilterNone to be notified of all events (this is also the default value).

The completed creation of our location manage looks like this:

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
    // Override point for customization after application launch.
    self.window.backgroundColor = [UIColor whiteColor];
    [self.window makeKeyAndVisible];
 
    if(self.locationManager==nil){
        _locationManager=[[CLLocationManager alloc] init];
        //I'm using ARC with this project so no need to release
 
        _locationManager.delegate=self;
        _locationManager.purpose = @"We will try to tell you where you are if you get lost";
        _locationManager.desiredAccuracy=kCLLocationAccuracyBest;
        _locationManager.distanceFilter=500;
        self.locationManager=_locationManager;
    }
 
    return YES;
}

If you run this now, you should not notice any change in the way your application runs, you also won’t start receiving location information just yet. That comes next…

Starting Location Services

Now that we have our location manager configured, we want to start getting the location. To start the standard location service, you should first check to make sure that location services are enabled. This is done with a simple call to [CLLocationManager locationServicesEnabled] so after we set up our location manager above and before the return YES;, add the following code:

    if([CLLocationManager locationServicesEnabled]){
        [self.locationManager startUpdatingLocation];
    }

NOTE: If location services are not enabled and you start updating location services, the user will be prompted to enable location services. This could be annoying to the end user if they have to answer “No” every time your app launches.

If you run your app now, you will notice that the user is prompted to enable location services (and it will include the message from the .prompt property of our location manager object).

Receiving Location Changes

We’ve started location services, but now we need to start receiving updates to location changes. This is all done through the CLLocationManagerDelegate protocol. There are a number of available methods to implement for this delegate but the three most important are probably:

1. – locationManager:didUpdateToLocation:fromLocation:
2. – locationManager:didFailWithError:
3. – locationManager:didChangeAuthorizationStatus:

– locationManager:didUpdateToLocation:fromLocation:

Let’s start with receiving an update in location and how to handle that. In our App Delegate implementation file (.m), add the following method placeholder below the @synthesize … statements and above - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions method:

-(void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation{
 
}

One of the first things I like to do is check the timestamp of the newLocation detected. When you first start updating location services, the location manager will receive the last known location of the device, this could be hours or days old depending on the last time location services were used. In my apps, I like to make sure that I have a recent location. This following code will only use a location that has been found in the last 15.0 seconds:

    NSDate* eventDate = newLocation.timestamp;
    NSTimeInterval howRecent = [eventDate timeIntervalSinceNow];
    if (abs(howRecent) < 15.0)
    {
        //Location timestamp is within the last 15.0 seconds, let's use it!
    }

The next check that I like to perform is to see how accurate the newLocation is. This can be done by looking at the .horizontalAccuracy property. This property tells you how accurate your location information is. As I stated above, you can request to have very accurate locations but you are not guaranteed it. In the illustration below, the newLocation.coordinate is the location the device thinks it is, but in truth the orange circle of the .horizontalAccuracy says that it could be anywhere in that circle.

Your application’s need will determine how accurate of a location you need. Again, if you just need the city the user is in, you won’t need it to be as accurate as if you were trying to find something within walking distance. In the code below, I have set my accuracy threshold to 35.0 meters. This is pretty broad but I have found that it works well indoors as well as out. Insert the following code right after the comment //Location timestamp is within the last 15.0 seconds, let's use it!

        //Location timestamp is within the last 15.0 seconds, let's use it!
        if(newLocation.horizontalAccuracy<35.0){
            //Location seems pretty accurate, let's use it!
            NSLog(@"latitude %+.6f, longitude %+.6f\n",
                  newLocation.coordinate.latitude,
                  newLocation.coordinate.longitude);
            NSLog(@"Horizontal Accuracy:%f", newLocation.horizontalAccuracy);
 
            //Optional: turn off location services once we've gotten a good location
            [manager stopUpdatingLocation];
        }

The code above will print the new location to the console and then turn off location services. This is an optional step but if you don’t need location services anymore, it’s a smart thing to turn them off to conserve your user’s battery.

This is what our complete delegate method looks like:

-(void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation{
    NSDate* eventDate = newLocation.timestamp;
    NSTimeInterval howRecent = [eventDate timeIntervalSinceNow];
    if (abs(howRecent) < 15.0)
    {
        //Location timestamp is within the last 15.0 seconds, let's use it!
        if(newLocation.horizontalAccuracy<35.0){
            //Location seems pretty accurate, let's use it!
            NSLog(@"latitude %+.6f, longitude %+.6f\n",
                  newLocation.coordinate.latitude,
                  newLocation.coordinate.longitude);
            NSLog(@"Horizontal Accuracy:%f", newLocation.horizontalAccuracy);
 
            //Optional: turn off location services once we've gotten a good location
            [manager stopUpdatingLocation];
        }
    }
}

Now we can run the project again. If you didn’t authorize the app to use location services before, go ahead and do that now. We haven’t done anything with the location at this point except print it out to the console. If you don’t know how to see the console, make sure Xcode is the active window (NOT the simulator) and press ⌘⇧C

If you are running the project on the simulator and not a device, you may not see any results in the console window. This is because the simulator does not have location services turned on by default. You can simulate a location by selecting the location services simulation in the console window:

You can also simulate a location in the Simulator by using the Debug menu.

Once a location has been selected, you may need to restart the app to get the new location to show in the console window:

Because we built the location manager into the App Delegate, you can access the device’s current location anywhere in your code by including the AppDelegate header file (.h) in your view controller’s implementation file (.m):

#import "CFAAppDelegate.h"

Then whenever you need to access the location, you can use the following bit of code:

//Make sure location services are enabled before requesting the location
if([CLLocationManager locationServicesEnabled]){
 
    CFAAppDelegate *appDelegate=(CFAAppDelegate *)[UIApplication sharedApplication].delegate;
    CLLocation *currentLocation=appDelegate.locationManager.location;
 
    //Do what you want with the location...
}

About: Shawn Grimes
Shawn is a mobile app developer for ELC Technologies. He is a co-author of the book, iOS 5 Recipes: A Problem-Solution Approach (Recipes Apress). You can follow him on twitter @shawng. Shawn also works with high school students to teach them app development skills through the APPlied Club Program.

UIKit/UIKit.hp

Here are the sound files you will need to download for this tutorial:

• clapping-crowd-studio-01
• tennis-volley-01

Notice that all of the audio files have a .caf extension. This is the audio type all of your sound files must be in to be played by the iPhone. Luckily Apple has provided us a utility for converting audio to this format. You can read up on it here. It’s pretty straight forward, just open up a Terminal and type

/usr/bin/afconvert -f caff -d LEI16 {INPUT} {OUTPUT}

Where {INPUT} is the path to your input audio file and {OUTPUT} is the file you want it to save it to with a .caf extension.

Adding the Audio Files To You Project

Start by downloading these files. Then drag them to your Resources Folder inside of your project. You may also want to add a subfolder called Audio to keep organized. Make sure you check the box to copy the files into your project’s directory.

Add The AudioToolbox.framework to Your Project

Since we need to call functions within this framework, we will need to add it to our project. The best way I have found to locate a framework on my mac is to search for it. Right Click on the Frameworks folder in your project and select Add -> Existing Frameworks. In the search box type AudioToolbox.framework and select the framework among the search results. (Make sure you have Computer selected to search your entire computer)

When you find it, click Add. We are now ready to start coding…

Add the Header Declarations

Open up iTennisViewController.h and add the following code.

First we see an import for the AudioServices.h. This is needed to call the functions required for us to play audio. Next, we declare 2 SystemSoundID’s. These are basically just Integers (could actually use an int instead but you’d get a warning). Next, open up iTennishViewController.m and add the following code to synthesize these variables.

Now let’s initialize our sounds objects. Go to the viewDidLoad method and add the following code.

Pretty straight forward. The first line gets the path of the audio file. The next line converts the path to a CFURLRef. Finally, we load that audio file and associate it with the given sound ID. Notice we pass &clappingFileID. This is a pass by reference and allows the AudioServicesCreateSystemSoundID method to modify this variable. We do the same thing to load the volley sound. Now, let’s play the sounds.

Playing The Sounds

It’s actually quite simple to play the sounds we have loaded. Simply call the AudioServicesPlaySystemSound method and pass it the soundID of the file you want to play. So to play the clapping sound when someone scores, add this code to your reset method.

Notice, we are passing the clappingFileID to indicate we want to play the clapping sound. Now, add the following code to gameLoop to play the racquet sound when someone hits the ball.

Pretty straight forward Right? Now click Build and Go and check out the game audio. That concludes this tutorial. If you have any questions or comments, feel free to leave them in the comments section of this post or write them to me on Twitter. You can also download the sample code here

Happy iCoding!

]]> http://icodeblog.com/2009/05/04/iphone-game-programming-tutorial-part-4-basic-game-audio/feed/ 70 http://icodeblog.com/2008/11/05/a-great-iphone-coding-resource/ http://icodeblog.com/2008/11/05/a-great-iphone-coding-resource/#comments Wed, 05 Nov 2008 18:42:03 +0000 http://icodeblog.com/?p=544 Stanford is offering an iPhone development class this semester. On my journeys through the interwebs, I discovered a link to the site where the lectures for this class were posted (via delicious). So for those of you who already didn’t know this, here is a link to the lecture slides (with sample code). http://www.stanford.edu/class/cs193p/cgi-bin/index.php I hope you find the examples and instruction here very useful. Have a great day ...]]> I’m sure many of you are aware that Stanford is offering an iPhone development class this semester. On my journeys through the interwebs, I discovered a link to the site where the lectures for this class were posted (via delicious).

So for those of you who already didn’t know this, here is a link to the lecture slides (with sample code).

http://www.stanford.edu/class/cs193p/cgi-bin/index.php

I hope you find the examples and instruction here very useful. Have a great day and happy iCoding!

It looks like iCodeBlog is no longer illegal! Lol. Apple has just announced that they are doing away with their “F-ing” NDA (as it has been coined). This is great news for developers as we can now talk safely in the open about development for the iPhone without fear.

This pesky NDA has been annoying developers since the beginning of (iPhone Development) time. Maybe now, we will start seeing some great books being published for iPhone development.

Source: Engaget