How to randomize images in a page scrollview - ios

Question

I have 12 images, stored in an array...
I use this to output the image.
scrollView = [[UIScrollView alloc] init];
CGRect scrollFrame;
scrollFrame.origin.x = 0;
scrollFrame.origin.y = 0;
scrollFrame.size.width = WIDTH_OF_SCROLL_PAGE;
scrollFrame.size.height = HEIGHT_OF_SCROLL_PAGE;
scrollView = [[UIScrollView alloc] initWithFrame:scrollFrame];
scrollView.bounces = YES;
scrollView.pagingEnabled = YES;
scrollView.showsHorizontalScrollIndicator = NO;
scrollView.delegate = self;
scrollView.userInteractionEnabled = YES;
NSMutableArray *slideImages = [[NSMutableArray alloc] init];
[slideImages addObject:#"KODAK1.png"];
[slideImages addObject:#"KODAK2.png"];
[slideImages addObject:#"KODAK3.png"];
[slideImages addObject:#"KODAK4.png"];
[slideImages addObject:#"KODAK5.png"];
[slideImages addObject:#"KODAK6.png"];
[slideImages addObject:#"KODAK7.png"];
[slideImages addObject:#"KODAK8.png"];
[slideImages addObject:#"KODAK9.png"];
[slideImages addObject:#"KODAK10.png"];
[slideImages addObject:#"KODAK11.png"];
[slideImages addObject:#"KODAK12.png"];
srandom(time(NULL));
int x = arc4random() % 12;
for ( int i = 0 ;i<[slideImages count]; i++) {
//loop this bit
UIImageView *imageView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:[slideImages objectAtIndex:i]]];
imageView.frame = CGRectMake((WIDTH_OF_IMAGE * i) + LEFT_EDGE_OFSET, 0 , WIDTH_OF_IMAGE, HEIGHT_OF_IMAGE);
[scrollView addSubview:imageView];
[imageView release];
}
[scrollView setContentSize:CGSizeMake(WIDTH_OF_SCROLL_PAGE * ([slideImages count] +0), HEIGHT_OF_IMAGE)];
[scrollView setContentOffset:CGPointMake(0, 0)];
[self.view addSubview:scrollView];
[self.scrollView scrollRectToVisible:CGRectMake(WIDTH_OF_IMAGE,0,WIDTH_OF_IMAGE,HEIGHT_OF_IMAGE) animated:YES];
[super viewDidLoad]
How can i output random images in the UIView? as in there are 12 images, but each time i run the application, the app will start at a random image, but i will still be able to scroll through the images. i hope you guys understand my question.

Answer 1

You could "shuffle" the NSMutableArray each time you create it:
NSMutableArray *slideImages = [[NSMutableArray alloc] init];
...
[slideImages shuffle];
...
So each time you will be initializing the UIScrollView with a different order.
shuffle is not part of the SDK. For an sample implementation, please have a look to this:
#implementation NSMutableArray (Shuffling)
- (void)shuffle
{
static BOOL seeded = NO;
if(!seeded)
{
seeded = YES;
srandom(time(NULL));
}
NSUInteger count = [self count];
for (NSUInteger i = 0; i < count; ++i) {
// Select a random element between i and end of array to swap with.
int nElements = count - i;
int n = (random() % nElements) + i;
[self exchangeObjectAtIndex:i withObjectAtIndex:n];
}
}
#end
Import the header file containing you category declaration:
#interface NSMutableArray (Shuffling)
- (void)shuffle;
#end
wherever you want to use shuffle.