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POHow to Add an Array of UIImages to a Collection View
 

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  1. POHow to Add an Array of UIImages to a Collection View
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    <p>Thanks in advance for checking out this project and lending me a hand.<br></p> <h2>Storyboard Connections</h2> <p>I am trying to display an array of UIImages in my Collection View. I have connected everything in the storyboard. <br> My ViewController is both the delegate and dataSource for my Collection View. <br> My cell contains a UIImageView that has an IBOutlet in my custom cell's header file.<br><br></p> <h2>How the App Currently Works</h2> <ol> <li>The App creates an array of images from the wikipedia API based on a search by a user.</li> <li>Once the user types in his or her search, the ViewController passes the NSString off to the model (GetImageURL.h and GetImageURL.m.)</li> <li>This seems to be working based off the NSLogs that I am using.</li> <li>The Model passes it back to the controller once it has set up an array of UIImages.</li> <li>The ViewController then attempts to reload the collectionView's data and the app crashes.</li> </ol> <p>The error message looks like this:</p> <pre><code>*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'UICollectionView must be initialized with a non-nil layout parameter' *** First throw call stack: (0x1c97012 0x10d4e7e 0x1c96deb 0x518748 0x533b1b 0x533646 0xf9ff8 0xfa232 0x5338d5 0x29a4 0x3ef6 0xb13fb4 0xb13e67 0x30ca 0x49fb53f 0x4a0d014 0x49fd7d5 0x1c3daf5 0x1c3cf44 0x1c3ce1b 0x1bf17e3 0x1bf1668 0x18ffc 0x1b9d 0x1ac5) libc++abi.dylib: terminate called throwing an exception </code></pre> <p><br></p> <h1>My Question</h1> <p>I am wondering what I am doing wrong to create collectionView that causes it to crash upon a call later to reloadData. <br></p> <h1>Code</h1> <p>ViewController.h</p> <pre><code>#import &lt;UIKit/UIKit.h&gt; @interface ViewController : UICollectionViewController &lt;UICollectionViewDelegateFlowLayout, UICollectionViewDataSource, UIApplicationDelegate&gt; //receives a mutable array of UIImage(s) -(void)receiveArrayOfImages: (NSMutableArray *)arrayOfImages; @end </code></pre> <p><br> ViewController.m</p> <pre><code>#import "ViewController.h" #import "Cell.h" #import "GetImageURL.h" NSString *kCellID = @"cellID"; @interface ViewController () { UISearchBar *searchBar; } @property (nonatomic, strong) NSString *searchBarText; @property (strong, nonatomic) NSMutableArray *arrayOfImages; @end @implementation ViewController -(NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section { if ([self.arrayOfImages count] &gt; 0) { NSLog(@"return %d items for collection view", [self.arrayOfImages count]); return [self.arrayOfImages count]; } else { NSLog(@"returned 0 items for collection view"); return 0; } } - (UICollectionViewCell *)collectionView:(UICollectionView *)cv cellForItemAtIndexPath:(NSIndexPath *)indexPath { NSLog(@"cellForItemAtIndexPath"); Cell *cell = [cv dequeueReusableCellWithReuseIdentifier:kCellID forIndexPath:indexPath]; int row = [indexPath row]; cell.cellImage.image = [self.arrayOfImages objectAtIndex:row]; return cell; } - (void)viewDidLoad { [super viewDidLoad]; //Creates a Search Bar Button System Item. UIBarButtonItem *searchButton = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemSearch target:self action:@selector(tapSearchButton:)]; self.navigationItem.rightBarButtonItem = searchButton; } -(void)tapSearchButton:(id)sender { //Adds or takes away searchbar on navigationbar. if (!searchBar) { searchBar = [[UISearchBar alloc] initWithFrame:CGRectMake(-5.0, 0.0, 320.0, 44.0)]; searchBar.autoresizingMask = UIViewAutoresizingFlexibleWidth; UIView *searchBarView = [[UIView alloc] initWithFrame:CGRectMake(0.0, 0.0, 310.0, 44.0)]; searchBarView.autoresizingMask = 0; searchBar.delegate = self; //this line causes a warning. "Assigning to 'id&lt;UISearchBarDelegate&gt; from incompatible type 'ViewController *cons_strong" [searchBarView addSubview:searchBar]; self.navigationItem.titleView = searchBarView; [searchBar becomeFirstResponder]; } else { self.navigationItem.titleView = nil; searchBar = nil; } } - (void)searchBarSearchButtonClicked:(UISearchBar *)searchBar { GetImageURL *bookName = [[GetImageURL alloc] init]; bookName.bookName = [searchBar text]; //this line causes a warning. "Local declaration of 'searchBar' hides instance variable" NSLog(@"In ViewController, the book name is: %@", bookName.bookName); [bookName recieveBookUrl:bookName.bookName]; [self.view endEditing:YES]; } -(void)receiveArrayOfImages: (NSMutableArray *)arrayOfImages { //receives an array of UImages called arrayOfImages and sets it to self.arrayOfImages self.arrayOfImages = arrayOfImages; NSLog(@"This is the array of UIimages in ViewController.m: %@", self.arrayOfImages); [self.collectionView reloadData]; //This line causes the app the crash. "Reason: UICollectionView must be initialized with a non-nil layout parameter" } @end </code></pre> <p><br> Cell.h</p> <pre><code>#import &lt;UIKit/UIKit.h&gt; @interface Cell : UICollectionViewCell //UIImageView inside Custom Cell @property (strong, nonatomic) IBOutlet UIImageView *cellImage; @end </code></pre> <p><br> Cell.m</p> <pre><code>#import "Cell.h" @implementation Cell - (id)initWithCoder:(NSCoder *)coder { self = [super initWithCoder:coder]; if (self) { } return self; } @end </code></pre> <p><br> GetImageURL.h</p> <pre><code>#import &lt;Foundation/Foundation.h&gt; #import "ViewController.h" @interface GetImageURL : NSObject @property (strong, nonatomic) NSString *bookName; @property (strong, nonatomic) NSMutableArray *imageArray; -(void)recieveBookUrl:(NSString *)bookName; //recieves a string from the viewController that the user inputs @end </code></pre> <p><br> GetImageURL.m</p> <pre><code>#import "GetImageURL.h" @interface GetImageURL() @property (strong, nonatomic) NSString *pageID; @property (strong, nonatomic) NSMutableArray *imageUrlArray; @end @implementation GetImageURL //takes the string that the user entered and alters it to fit the wikipedia API format -(void)recieveBookUrl:(NSString *)bookName { self.imageUrlArray = [[NSMutableArray alloc] init]; self.imageArray = [[NSMutableArray alloc] init]; bookName = [bookName stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]; //or use string by replacing @" " with @"%20"; NSString *wikiAPI = @"http://en.wikipedia.org/w/api.php?format=json&amp;indexpageids&amp;action=query&amp;prop=images&amp;titles="; bookName = [wikiAPI stringByAppendingString:bookName]; NSURL *bookURL = [NSURL URLWithString:bookName]; //Plan to put this action in the background later dispatch_async(dispatch_get_main_queue(), ^() { NSData *data = [NSData dataWithContentsOfURL:bookURL]; [self performSelectorOnMainThread:@selector(getBookTitleApi:) withObject:data waitUntilDone:YES]; }); } //first part of the API sucessfully gets the padeID and all the images returned by the API. -(void)getBookTitleApi: (NSData *)data { NSError *error; NSDictionary *json = [NSJSONSerialization JSONObjectWithData:data options:kNilOptions error:&amp;error]; NSDictionary *parseQueryBookTitle = [json objectForKey:@"query"]; NSArray *parsePageIdsBookTitle = [parseQueryBookTitle objectForKey:@"pageids"]; for (NSDictionary *pageIdBookTitle in parsePageIdsBookTitle) { self.pageID = [NSString stringWithFormat:@"%@", pageIdBookTitle]; } NSDictionary *parsePagesBookTitle = [parseQueryBookTitle objectForKey:@"pages"]; NSDictionary *parsePageIdBookTitle = [parsePagesBookTitle objectForKey:self.pageID]; NSDictionary *parseImagesBookTitle = [parsePageIdBookTitle objectForKey:@"images"]; NSDictionary *valueTitleBookTitle = [parseImagesBookTitle valueForKey:@"title"]; for (NSDictionary *imageFilenames in valueTitleBookTitle) { NSString *imageFilename = [NSString stringWithFormat:@"%@", imageFilenames]; imageFilename = [imageFilename substringFromIndex:5]; imageFilename = [imageFilename stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]; //or use string by replacing @" " with @"%20"; NSString *wikiImageAPI = @"http://en.wikipedia.org/w/api.php?action=query&amp;format=json&amp;indexpageids&amp;prop=imageinfo&amp;iiprop=url&amp;titles=Image:"; imageFilename = [wikiImageAPI stringByAppendingString:imageFilename]; NSURL *imageFilenameUrl = [NSURL URLWithString:imageFilename]; NSData *data = [NSData dataWithContentsOfURL:imageFilenameUrl]; [self performSelectorOnMainThread:@selector(getImageApi:) withObject:data waitUntilDone:YES]; } //Uses the URLs to create an NSData object and then uses that data to create a UIImage which is added to a Mutable Array for (NSString *jpgURL in self.imageUrlArray) { NSURL *imageURL = [NSURL URLWithString:jpgURL]; NSLog(@"This is an imageURL in GetImageURL.m: %@", imageURL); NSData *data = [NSData dataWithContentsOfURL:imageURL]; UIImage *image = [UIImage imageWithData:data]; [self.imageArray addObject:image]; } NSLog(@"The array of images in GetImageURL.m contains %d images called %@", [self.imageArray count], self.imageArray); ViewController *view = [[ViewController alloc] init]; [view receiveArrayOfImages:self.imageArray]; //sends the array of images to the View Controller //objects removed from array so that next user search can start over [self.imageArray removeAllObjects]; [self.imageUrlArray removeAllObjects]; } //Uses the image filenames from the first section and gets the specific URLS for the image. Limits results to .jpg images -(void)getImageApi: (NSData *)data { NSError *error; NSDictionary *json = [NSJSONSerialization JSONObjectWithData:data options:kNilOptions error:&amp;error]; NSDictionary *parseQueryImage = [json objectForKey:@"query"]; NSDictionary *parsePageIdsImage = [parseQueryImage objectForKey:@"pageids"]; for (NSString *pageIdImage in parsePageIdsImage) { NSDictionary *parsePagesImage = [parseQueryImage objectForKey:@"pages"]; NSDictionary *parsePageIdImage = [parsePagesImage objectForKey:pageIdImage]; NSDictionary *parseImageInfoImage = [parsePageIdImage objectForKey:@"imageinfo"]; NSDictionary *valueImageInfoUrlsImage = [parseImageInfoImage valueForKey:@"url"]; for (NSString *valueImageInfoUrlImage in valueImageInfoUrlsImage) { if ([valueImageInfoUrlImage hasSuffix:@".jpg"]) { [self.imageUrlArray addObject:valueImageInfoUrlImage]; } } } } @end </code></pre> <p><br></p> <p>Sorry for dumping all the code in here. I figured it would be easier if it was all there. Maybe it will be helpful to someone else too.</p> <p>Thanks!</p>
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