Add new image and remove old image from image view - ios

Question

In my ipad app, i has 200 images and i add these images into an array.
Then add this array into image view by looping.
Then, i add this image view as sub view of scroll view.
When i open app, my app is crash.
I try with reducing image size. But, it didn't work.
One of my friend told firstly i should add only image1 and image2.
When user scroll image1, then it show image2.
After that image1 is remove from image view.
And add image3 to image view.
He told it can maintain memory usage.
But, i don't know how can i do that? :D
Please, give me some example.
Thanks in advance.
My code is here,
- (void)viewDidLoad
{
[super loadView];
self.view.backgroundColor = [UIColor grayColor];
UIScrollView *ScrollView = [[UIScrollView alloc] initWithFrame:CGRectMake(0, 44, self.view.frame.size.width, self.view.frame.size.height)];
ScrollView.pagingEnabled = YES;
// Create a UIImage to hold Info.png
UIImage *image1 = [UIImage imageNamed:#"Image-001.jpg"];
UIImage *image2 = [UIImage imageNamed:#"Image-002.jpg"];
UIImage *image200 = [UIImage imageNamed:#"Image-200.jpg"];
NSArray *images = [[NSArray alloc] initWithObjects:image1,image2,...,image200,nil];
NSInteger numberOfViews = 200;
for (int i = 0; i < numberOfViews; i++)
{
CGFloat xOrigin = i * self.view.frame.size.width;
UIImageView *ImageView = [[UIImageView alloc] initWithFrame:CGRectMake(xOrigin, 0, self.view.frame.size.width, self.view.frame.size.height-44)];
[ImageView setImage:[images objectAtIndex:i]];
[ScrollView addSubview:ImageView];
}
ScrollView.contentSize = CGSizeMake(self.view.frame.size.width * numberOfViews, self.view.frame.size.height);
[self.view addSubview:ScrollView];

Answer 1

It looks like you're accessing the images array at indexes 0..200, but it contains only three elements. Either set numberOfViews = 3;, or index into the array like this:
ImageView.image = images[i%3];
The modulo index will cause you to add each of the three images in a repeating sequence and still let you test with a larger number of scrollView subviews. I doubt that your crash is about memory with only 200 images, unless they are super-huge ones.

Answer 2

You should use a table view to display your images. You don't want to create an array of all those images, because that puts all those images into memory -- not a good thing. You don't even need to create an array to hold the names, since they have names you can easily construct from an integer (which you can get from indexPath.row in the tableView:cellForRowAtIndexPath: method). Something like this:
- (void)viewDidLoad {
[super viewDidLoad];
[self.tableView registerClass:[UITableViewCell class] forCellReuseIdentifier:#"Cell"];
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
return 200;
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
static NSString *CellIdentifier = #"Cell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier forIndexPath:indexPath];
NSString *imageName = [NSString stringWithFormat:#"Image-%.3d.jpg",indexPath.row +1];
UIImage *image = [UIImage imageNamed:imageName];
cell.imageView.image = image;
return cell;
}
This example just uses the cell's default imageView to show the images, which is pretty small. You would probably want to create a custom cell with a larger image view in it (or a couple side by side if you want more than one image per row).