core background

An Objective-C API inspired by iOS 7 and the Yahoo Weather App. Location-based Flickr photos in background UIImageView are Gaussian blurred by a UIScrollView while scrolling over foreground iPhone content.

justinmfischer

565

Objective-C

Example

Sample project .gif (4.1MB)

##Overview

CoreBackground is a set of Objective-C classes inspired by the iOS Yahoo Weather App. It provides iOS location-based Flickr backgrounds with Gaussian blur light effects for iPhone.

As one scrolls over the foreground a Gaussian blur light effect is applied to the background. This provides for an engaging location-based UX while at the same time providing a canvas to apply readable content to the foreground. CoreBackground is a non-blocking “event-based” Objective-C block API and all rendering occurs in backing stores to preserve the main run loop. Make it be the foundation of your next iOS project today.

Since CoreBackground uses public licenses to retrieve content from Flickr we display the owner’s copyright information along with a link to encourage discoverability.

Getting Started

CoreBackground is comprised of 3 main Objective-C singleton managers all within the CBG header file (CBG.h).

CBGLocationManager : Provides cacheable location-based information.
CBGFlickrManager : Provides cacheable Flickr API content.
CBGStockPhotoManager : Provides local image content in case of reachability issues.

Prior to using CoreBackground a valid Flickr API key and shared secret is required. The sample project will successfully build (LLVM - Warning) without this information but will fall back to stock photos. The Flickr API key and shared secret can be obtained here. As of this writing Flickr restricts free (Non-Commercial) accounts to 3600 request per hour. Please make the following modifications below.

(CBGConstants.h)

//Flickr Auth
#define OBJECTIVE_FLICKR_API_KEY @"Ch@ngeMe"
#define OBJECTIVE_FLICKR_API_SHARED_SECRET @"Ch@ngeMe"

The constants file also contains a value to provide searchable Flickr photo tags. The sample project uses “bike” and will match any comma separated values. Example: “bike,ride,outdoor”

//Flickr Search
#define KFlickrSsearchTags @"bike"

Required Linked Frameworks

Accelerate.framework
CoreLocation.framework
CFNetwork.framework
SystemConfiguration.framework

Code : Sample Project

The CoreBackground sample project demonstrates how these Objective-C classes can be used to achieve location-based background content to drive discoverability and local engagement.

While one could subclass UIViewController to provide higher orders of abstraction CoreBackground was specifically designed to be loosely coupled and not bound to a particular view hierarchy. This design pattern encourages community modifications and higher adoption rates.

ViewController.m

- (void) viewDidLoad {
    
    [super viewDidLoad];

    //ScrollView content size
    if([CBGUtil is4InchIphone]) {
        self.scrollView.contentSize = CGSizeMake(320, 720);
    } else {
        self.scrollView.contentSize = CGSizeMake(320, 580);
    }
    
    //Initial stock photos from bundle
    [[CBGStockPhotoManager sharedManager] randomStockPhoto:^(CBGPhotos * photos) {
        [self crossDissolvePhotos:photos withTitle:@""];
    }];
    
    //Retrieve location and content from Flickr
    [self retrieveLocationAndUpdateBackgroundPhoto];
    
    //Schedule updates
    self.timer = [NSTimer scheduledTimerWithTimeInterval:kTimerIntervalInSeconds target:self selector:@selector(retrieveLocationAndUpdateBackgroundPhoto)userInfo:nil repeats:YES];
}

- (void) retrieveLocationAndUpdateBackgroundPhoto {
    
    //Location
    [[CBGLocationManager sharedManager] locationRequest:^(CLLocation * location, NSError * error) {
        
        [self.activityIndicator startAnimating];
        
        if(!error) {
            
            //Flickr 
            [[CBGFlickrManager sharedManager] randomPhotoRequest:^(FlickrRequestInfo * flickrRequestInfo, NSError * error) {
                
                if(!error) {
                    self.userPhotoWebPageURL = flickrRequestInfo.userPhotoWebPageURL;
                    
                    [self crossDissolvePhotos:flickrRequestInfo.photos withTitle:flickrRequestInfo.userInfo];
                    [self.activityIndicator stopAnimating];
                } else {
                    
                    //Error : Stock photos
                    [[CBGStockPhotoManager sharedManager] randomStockPhoto:^(CBGPhotos * photos) {
                        [self crossDissolvePhotos:photos withTitle:@""];
                    }];
                    
                    [self.activityIndicator stopAnimating];
                    
                    NSLog(@"Flickr: %@", error.description);
                }
            }];
        } else {
            
            //Error : Stock photos
            [[CBGStockPhotoManager sharedManager] randomStockPhoto:^(CBGPhotos * photos) {
                [self crossDissolvePhotos:photos withTitle:@""];
            }];
            
            [self.activityIndicator stopAnimating];
            
            NSLog(@"Location: %@", error.description);
        }
    }];
}

- (void) crossDissolvePhotos:(CBGPhotos *) photos withTitle:(NSString *) title {
    [UIView transitionWithView:self.backgroundPhoto duration:1.0f options:UIViewAnimationOptionTransitionCrossDissolve animations:^{
        
        self.backgroundPhoto.image = photos.photo;
        self.backgroundPhotoWithImageEffects.image = photos.photoWithEffects;
        self.photoUserInfoBarButton.title = title;
        
    } completion:NULL];
}

- (IBAction) launchFlickrUserPhotoWebPage:(id) sender {
    if([self.photoUserInfoBarButton.title  length] > 0) {
        [[UIApplication sharedApplication] openURL:self.userPhotoWebPageURL];
    }
}

- (void) scrollViewDidScroll:(UIScrollView *) scrollView {
    if(scrollView.contentOffset.y >= 0 && scrollView.contentOffset.y <= 80.0) {
        float percent = (scrollView.contentOffset.y / 80.0);
        
        self.backgroundPhotoWithImageEffects.alpha = percent;
        
    } else if (scrollView.contentOffset.y > 80.0){
        self.backgroundPhotoWithImageEffects.alpha = 1;
    } else if (scrollView.contentOffset.y < 0) {
        self.backgroundPhotoWithImageEffects.alpha = 0;
    }
}

Cache & Timeout Details

CoreBackground provides location and Flickr search caching to save power, reduce bandwidth and most important to preserve the UX. The default settings cache location information for 30 minuets and Flickr search results for 15 minuets.

Location requests will timeout after 10 seconds and requests to Flickr after 15 seconds. These settings can be modified as show below.

(CBGConstants.h)

//Location
#define kLocationInvalidateCacheTimeoutDurationInSeconds 1800 //30min (60 * 30)
#define kLocationQuitTimeoutDurationInSeconds 10

//Flickr
#define kFlickrSearchInvalidateCacheTimeoutDurationInSeconds 900 //15min (60 * 15)
#define kFlickrSearchQuitTimeoutDurationInSeconds 15

Stock Photos

The CBGStockPhotoManager provides random local stock photos when there are reachability issues. The manager looks at local Xcode folder reference named “StockPhotos” and iterates over any photos in the collection that conform to the following naming convention.

{3 digit serial-number}-StockPhoto-320x568.png
{3 digit serial-number}[email protected]

Example:
000-StockPhoto-320x568.png
[email protected]
001-StockPhoto-320x568.png
[email protected]
...

Thread-Safety

CoreBackground is intended to be called from a timer which is scheduled on the main run loop. Although API block callbacks will be dispatched to the main queue there are no thread-safe guaranties.

History

Initial release : 6/29/2013

Acknowledgements

Special thanks to Matt Martindale of Show Pony Apps, LLC for providing architectural guidance.

Copyright and Software License

ObjectiveFlickr : Lukhnos D. Liu.
LFWebAPIKit : Lukhnos D. Liu and Lithoglyph Inc.
UIImage Alpha, Resize, RoundedCorner Category Methods : Trevor Harmon
UIImage Image Effects Category Methods : Apple, Inc.

The MIT License (MIT)

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the “Software”), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

Contact

Justin M Fischer : [email protected]