I'm creating some kind of image gallery. User can swipe between photo's. (Its just the concept, i know there are good library's out there that can handle this, but it's just to explain the concept).
I'm loading in 3 UIImageView, and i'm constantly reusing them. (Lazy loading). Problem is, when i change the image dynamiccaly from one imageview, and keep changing it, the memory is filling up. It's like it does not releases previous attached images. I'm using an array of UIImages that I already downloaded from some kind of web service.
As i load my view, i'm allocing and init my UIImageView, then I add it to the view.
UIImageView* _imgView;
NSArray* _imgArray;
So this array contains UIImage
-(void)changeImageIndex: (int) i
{
_imgView.image = [_imgArray objectAtIndex:i];
}
if i keep changing the imageindex, memory just gets filled up and filled up.. :s.
My project is ARC enabled.
Somebody has a clue how to solve it?
The image is added (actually changed) by this method:
-(void)setCurrentMovie:(GFilm*)film
{
_currentMovie = nil;
_currentMovie = film;
_posterView.image = nil;
[_youtubeView loadHTMLString:#"" baseURL:nil];
[_youtubeView stopLoading];
[_youtubeView setDelegate:nil];
[[NSURLCache sharedURLCache] removeAllCachedResponses];
[_scrollView setContentOffset:CGPointMake(0, 0) animated:NO];
CGFloat leftHeight = 0.f;
_leftView.frame = CGRectMake(10, 10, 110, 205);
leftHeight += _leftView.frame.size.height;
_posterView.frame = CGRectMake(0, 0, _leftView.frame.size.width, _leftView.frame.size.height - 40);
GImage* img = (GImage*)[_currentMovie.imageList objectAtIndex:0];
//_posterView.image = img.localImage;
//#autoreleasepool {
_posterView.image = [UIImage imageWithData:UIImagePNGRepresentation(img.localImage)];
_btnVertoningen.frame = CGRectMake(0, _posterView.frame.origin.y + _posterView.frame.size.height + 5, _leftView.frame.size.width, 35);
_posterView.userInteractionEnabled = YES;
UITapGestureRecognizer *singleTap = [[UITapGestureRecognizer alloc] initWithTarget:self action:#selector(posterClick)];
singleTap.numberOfTapsRequired = 1;
[_posterView addGestureRecognizer:singleTap];
[_leftView addSubview:_posterView];
CGFloat rightHeight = 0.f;
_rightView.frame = CGRectMake(_leftView.frame.origin.x + _leftView.frame.size.width + 5, _leftView.frame.origin.y, self.view.frame.size.width - (_leftView.frame.size.width + _leftView.frame.origin.x) - 15, 1);
_lblRegie.frame = CGRectMake(0, rightHeight, 48, 16);
NSMutableString* text = [[NSMutableString alloc]init];
NSArray* arr = _currentMovie.directorList;
etc.....
}
Probably your app have memory leak. Try use imageWithContentsOfFile instead of imageNamed:
_imgView.image = [UIImage imageWithContentsOfFile:imagePath];
Another possibility to have memory leaks with ARC is using a separate thread without an autorelease pool set up. Check this link:
https://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/MemoryMgmt/Articles/mmAutoreleasePools.html:
Related
I have an array with dictionaries in it. Each dictionary contains UIImage & String values.
But when I try to delete object using
[arr removeObjectAtIndex:button.tag];
then it just decreases the count but image (Object) is not deleted.
So, my Images are overlapping when try to delete.
It also creates problem when I try to add objects in the array
[arr insertObject:dict atIndex:0];
so, I used
[_postObj.arr_images addObject:dict]; instead of insertObject
Help me to solve this
Objects use reference counting and both NSMutableArray and UIImageView will retain the UIImage object.
This means that removing it from the array will not automatically remove it from the UIImageView and you must remove it from both explicitly:
[arr removeObjectAtIndex:button.tag];
_imageView.image = nil;
Problem is in your frame setting of UIImageView. Please try using below code (not tested by myself) and see if this fixes the issue for you. Basically, I am adjusting X position of images based on previous image's width.
CGFloat imageXM = 5.0;
CGFloat imageXPos = 0;
for (UIImage *image in arr_images) {
CGRect imageFrame = CGRectMake(imageXPos + imageXM, 0.0, image.size.width, image.size.height);
imageXPos = imageXPos + image.size.width;
UIImageView *imageView = [[UIImageView alloc] initWithFrame:imageFrame];
imageView.contentMode = UIViewContentModeScaleAspectFit;
imageView.image = image;
[scl addSubview:imageView];
}
As in your code
[picker dismissViewControllerAnimated:YES completion:^{
[arr_images insertObject:chosenImage atIndex:0];
[self scrollImages_Setup2];
}];
[arr_images insertObject:chosenImage atIndex:0]; that means you need only one image to display on scroll view. Then why you take a loop:
-(void)scrollImages_Setup2
{
for (int k=0; k<arr_images.count; k++) {
UIImageView *imageView = [[UIImageView alloc] initWithFrame:CGRectMake((CGRectGetWidth(scl.frame) * k) + CGRectGetWidth(scl.frame), 0, CGRectGetWidth(scl.frame), CGRectGetHeight(scl.frame))];
imageView.contentMode = UIViewContentModeScaleAspectFit;
imageView.image=[arr_images objectAtIndex:k] ;
[scl addSubview:imageView];
}
scl.contentSize = CGSizeMake((CGRectGetWidth(scl.frame) * arr_images.count)+CGRectGetWidth(scl.frame), CGRectGetHeight(scl.frame));
}
You just right the code only for display the Image. you don't need to scroll view for displaying only one image. I think you are not clear what you want.
Your problem regarding the overwriting the images because of loop. so remove the loop, when you display a single image. Please remove the scrollview contentSize, because image_array will increase, when you add the multiple images in array and size width will be large. so remove arr_images.count as well.
I want to animate an image view in circular path and on click of image that image view need to change the new image. My problem is the images i allocated to the image view is not deallocated. And app receives memory warning and crashed. I surfed and tried lot of solutions for this problem but no use. In my case i need to create all ui components from Objective c class. Here am posting the code for creating image view and animation.
#autoreleasepool {
for(int i= 0 ; i < categories.count; i++)
{
NSString *categoryImage = [NSString stringWithFormat:#"%#_%ld.png",[categories objectAtIndex:i],(long)rating];
if (paginationClicked) {
if([selectedCategories containsObject:[categories objectAtIndex:i]]){
categoryImage = [NSString stringWithFormat:#"sel_%#",categoryImage];
}
}
UIImageView *imageView = [[UIImageView alloc] init];
imageView.image = [self.mySprites objectForKey:categoryImage];
imageView.contentMode = UIViewContentModeScaleAspectFit;
imageView.clipsToBounds = NO;
[imageView sizeToFit];
imageView.accessibilityHint = [categories objectAtIndex:i];
// imageView.frame = CGRectMake(location.x+sin(M_PI/2.5)*(self.view.frame.size.width*1.5),location.y+cos(M_PI/2.5)*(self.view.frame.size.width*1.5) , 150, 150);
imageView.userInteractionEnabled = YES;
imageView.multipleTouchEnabled = YES;
UITapGestureRecognizer *singleTap = [[UITapGestureRecognizer alloc] initWithTarget:self
action:#selector(categoryTapGestureCaptured:)];
singleTap.numberOfTapsRequired = 1;
[imageView addGestureRecognizer:singleTap];
[categoryView addSubview:imageView];
CAKeyframeAnimation *animation = [CAKeyframeAnimation animationWithKeyPath:#"position"];
UIBezierPath *path = [UIBezierPath bezierPath];
[path addArcWithCenter:location
radius:self.view.frame.size.width*1.5
startAngle:0.8
endAngle:-0.3+(0.1*(i+1))
clockwise:NO];
animation.path = path.CGPath;
imageView.center = path.currentPoint;
animation.fillMode = kCAFillModeForwards;
animation.removedOnCompletion = NO;
animation.duration = 1+0.25*i;
animation.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseIn];
// Apply it
[imageView.layer addAnimation:animation forKey:#"animation.trash"];
}
}
And this is the code to change the image on click.
for (UIImageView *subview in subviews) {
NSString *key = [NSString stringWithFormat:#"%#_%ld.png",subview.accessibilityHint,(long)rating];
if ([SelectedCategory isEqualToString:subview.accessibilityHint]) {
NSString *tempSubCategory = [categoryObj objectForKey:SelectedCategory];
if([selectedCategories containsObject:SelectedCategory]){
subview.image = [self.mySprites objectForKey:key];
[selectedCategories removeObject:SelectedCategory];
if (tempSubCategory.length != 0) {
subCategoriesAvailable = subCategoriesAvailable-1;
}
[self showNoPagination:subCategoriesAvailable+2];
}else{
if(selectedCategories.count != 2){
key = [NSString stringWithFormat:#"sel_%#",key];
subview.image = [self.mySprites objectForKey:key];
[selectedCategories addObject:SelectedCategory];
if ([SelectedCategory isEqualToString:#"Other"]) {
[self showCommentDialog];
}else{
if (tempSubCategory.length != 0) {
subCategoriesAvailable = subCategoriesAvailable+1;
}
[self showNoPagination:subCategoriesAvailable+2];
}
}
}
[self disableCategories];
break;
}
}
And i don't know what am doing wrong here. I tried nullifying on for loop but no use.
Code which i used for removing the image view
UIView *categoryView = [self.view viewWithTag:500];
NSArray *subviews = [categoryView subviews];
for (UIImageView *subview in subviews) {
if(![selectedCategories containsObject:subview.accessibilityHint]){
[subview removeFromSuperview];
subview.image = Nil;
}
}
Adding sprite reader code for reference
#import "UIImage+Sprite.h"
#import "XMLReader.h"
#implementation UIImage (Sprite)
+ (NSDictionary*)spritesWithContentsOfFile:(NSString*)filename
{
CGFloat scale = [UIScreen mainScreen].scale;
NSString* file = [filename stringByDeletingPathExtension];
if ([[UIScreen mainScreen] respondsToSelector:#selector(displayLinkWithTarget:selector:)] &&
(scale == 2.0))
{
file = [NSString stringWithFormat:#"%##2x", file];
}
NSString* extension = [filename pathExtension];
NSData* data = [NSData dataWithContentsOfFile:[NSString stringWithFormat:#"%#.%#", file,extension]];
NSError* error = nil;
NSDictionary* xmlDictionary = [XMLReader dictionaryForXMLData:data error:&error];
NSDictionary* xmlTextureAtlas = [xmlDictionary objectForKey:#"TextureAtlas"];
UIImage* image = [UIImage imageWithContentsOfFile:[NSString stringWithFormat:#"%#.%#", file,[[xmlTextureAtlas objectForKey:#"imagePath"]pathExtension]]];
CGSize size = CGSizeMake([[xmlTextureAtlas objectForKey:#"width"] integerValue],
[[xmlTextureAtlas objectForKey:#"height"] integerValue]);
if (!image || CGSizeEqualToSize(size, CGSizeZero)) return nil;
CGImageRef spriteSheet = [image CGImage];
NSMutableDictionary* tempDictionary = [[NSMutableDictionary alloc] init];
NSArray* xmlSprites = [xmlTextureAtlas objectForKey:#"sprite"];
for (NSDictionary* xmlSprite in xmlSprites)
{
CGRect unscaledRect = CGRectMake([[xmlSprite objectForKey:#"x"] integerValue],
[[xmlSprite objectForKey:#"y"] integerValue],
[[xmlSprite objectForKey:#"w"] integerValue],
[[xmlSprite objectForKey:#"h"] integerValue]);
CGImageRef sprite = CGImageCreateWithImageInRect(spriteSheet, unscaledRect);
// If this is a #2x image it is twice as big as it should be.
// Take care to consider the scale factor here.
[tempDictionary setObject:[UIImage imageWithCGImage:sprite scale:scale orientation:UIImageOrientationUp] forKey:[xmlSprite objectForKey:#"n"]];
CGImageRelease(sprite);
}
return [NSDictionary dictionaryWithDictionary:tempDictionary];
}
#end
Please help me to resolve this. Thanks in advance.
It looks like all the images are being retained by the dictionary(assumption) self.mySprites, as you are loading them with the call imageView.image = [self.mySprites objectForKey:categoryImage];
If you loaded the images into the dictionary with +[UIImage imageNamed:], then the dictionary initially contains only the compressed png images. Images are decompressed from png to bitmap as they are rendered to the screen, and these decompressed images use a large amount of RAM (that's the memory usage you're seeing labeled "ImageIO_PNG_Data"). If the dictionary is retaining them, then the memory will grow every time you render a new one to the screen, as the decompressed data is held inside the UIImage object retained by the dictionary.
Options available to you:
Store the image names in the self.mySprites dictionary, and load the images on demand. You should be aware that +[UIImage imageNamed:] implements internal RAM caching to speed things up, so this might also cause memory issues for you if the images are big, as the cache doesn't clear quickly. If this is an issue, consider using +[UIImage imageWithContentsOfFile:], although it requires some additional code (not much), which doesn't cache images in RAM.
Re-implement self.mySprites as an NSCache. NSCache will start throwing things out when the memory pressure gets too high, so you'll need to handle the case that the image is not there when you expect it to be, and load it from disk (perhaps using the above techniques)
CAKeyframeAnimation inherits from CAPropertyAnimation which in tern is inherited from CAAnimation.
If you see the delegate of CAAnimation class, it is strongly referenced as written below as it is declared -
/* The delegate of the animation. This object is retained for the
* lifetime of the animation object. Defaults to nil. See below for the
* supported delegate methods. */
#property(strong) id delegate;
Now you have added the reference of animation on imageView.layer, doing so the reference of imageView.layer will be strongly retained by CAAnimation reference.
Also you have set
animation.removedOnCompletion = NO;
which won't remove the animation from layer on completion
So if you are done with a image view then first removeAllAnimations from its layer and then release the image view.
I think as the CAAnimation strongly refers the imageView reference(it would also have increased it's retain count) and this could be the reason that you have removed the imageView from superview, after which it's retain count would still not be zero, and so leading to a leak.
Is there any specific requirement to set
animation.removedOnCompletion = NO;
since, setting
animation.removedOnCompletion = YES;
could solve the issue related to memory leak.
Alternatively, to resolve memory leak issue you can remove the corresponding animation on corresponding imageView' layer, by implementing delegate of CAAnimation, like as shown below -
/* Called when the animation either completes its active duration or
* is removed from the object it is attached to (i.e. the layer). 'flag'
* is true if the animation reached the end of its active duration
* without being removed. */
- (void)animationDidStop:(CAAnimation *)anim finished:(BOOL)flag {
if (flag) {
NSLog(#"%#", #"The animation is finished. Do something here.");
}
//Get the reference of the corresponding imageView
[imageView.layer removeAnimationForKey:#"animation.trash"];
}
UIView *categoryView = [self.view viewWithTag:500];
NSArray *subviews = [categoryView subviews];
for (UIImageView *subview in subviews) {
if(![selectedCategories containsObject:subview.accessibilityHint]){
[subview.layer removeAnimationForKey:#"animation.trash"]; // either this
//or// [subview.layer removeAllAnimations]; //alternatively
[subview removeFromSuperview];
subview.image = Nil;
}
}
I'm having trouble getting my head around this; I've looked around for answers on here but either nothing directly applies to my question or I just can't make sense of it. (I am relatively new to this, so apologise if there is an obvious answer.)
I am inserting an array of UIImages (contained within a UIImageView) into a UIScrollView. I can programmatically scroll to points in the ScrollView, but I need to be able to identify by name which image is currently being shown after scrolling (so I can compare the image to one in another ScrollView).
How I have created my arrays and added the images to the ImageView and ScrollView is below.
ViewController.m
-(void)viewDidLoad {
...
// Store the names as strings
stringArr = [[NSMutableArray arrayWithObjects:
#"img0",
#"img1",
#"img2",
#"img3",
nil] retain];
// Add images to array
dataArr = [[NSMutableArray arrayWithObjects:
[UIImage imageNamed:[stringArr objectAtIndex:0]],
[UIImage imageNamed:[stringArr objectAtIndex:1]],
[UIImage imageNamed:[stringArr objectAtIndex:2]],
[UIImage imageNamed:[stringArr objectAtIndex:3]],
nil] retain];
// Use a dictionary to try and make it possible to retrieve an image by name
dataDictionary = [NSMutableDictionary dictionaryWithObjects:dataArr forKeys:stringArr];
i = 0;
currentY = 0.0f;
// Set up contents of scrollview
// I'm adding each of the four images four times, in a random order
for (imageCount = 0; imageCount < 4; imageCount++) {
// Add images from the array to image views inside the scroll view.
for (UIImage *image in reelDictionary)
{
int rand = arc4random_uniform(4);
UIImage *images = [dataArr objectAtIndex:rand];
imgView = [[UIImageView alloc] initWithImage:images];
imgView.contentMode = UIViewContentModeScaleAspectFit;
imgView.clipsToBounds = YES;
// I have tried to use this to tag each individual image
imgView.tag = i;
i++;
CGRect rect = imgView.frame;
rect.origin.y = currentY;
imgView.frame = rect;
currentY += imgView.frame.size.height;
[scrollReel1 addSubview:reel1_imgView];
[reel1_imgView release];
}
}
scrollReel.contentSize = CGSizeMake(100, currentY);
[self.view addSubview:scrollReel];
...
}
This is how I am working out where I am in the ScrollView (currentOffset), and also exactly which image I need to retrieve (symbolNo). The value of symbolNo is correct when I test it, but I am unsure how to use the value with respect to image name retrieval.
NSInteger currentOffset = scrollReel.contentOffset.y;
NSInteger symbolNo = (currentOffset / 100) + 1;
Thanks in advance for any assistance.
There is no way to do this. The UIImage object doesn't store its name once it's loaded.
You could get around this by using the tag property on the image views if all your images have numerical names.
Otherwise you'll need to find a new way to model your data.
You basically need the reverse mapping of what you had. Here is a quick and dirty solution
NSMutableDictionary *indexToImageMap = [NSMutableDictionary new];
for (imageCount = 0; imageCount < 4; imageCount++) {
// Add images from the array to image views inside the scroll view.
for (UIImage *image in reelDictionary)
{
int rand = arc4random_uniform(4);
UIImage *images = [dataArr objectAtIndex:rand];
imgView = [[UIImageView alloc] initWithImage:images];
imgView.contentMode = UIViewContentModeScaleAspectFit;
imgView.clipsToBounds = YES;
// I have tried to use this to tag each individual image
imgView.tag = i;
i++;
[indexToImageMap setObject:imgView forKey:[NSNumber numberWithInt:i];
CGRect rect = imgView.frame;
rect.origin.y = currentY;
imgView.frame = rect;
currentY += imgView.frame.size.height;
[scrollReel1 addSubview:reel1_imgView];
[reel1_imgView release];
}
}
And to look it up you do
NSInteger currentOffset = scrollReel.contentOffset.y;
NSInteger symbolNo = (currentOffset / 100) + 1;
NSImage *image = [indexToImageMap objectForKey:[NSNumber numberWithInt:symbolNo]];
Subclass image view and add imageName property. if i understand what you are asking this should work.
#import <UIKit/UIKit.h>
#interface myImageView : UIImageView
{
__strong NSString *imageName;
}
#property (strong) NSString *imageName;
#end
#import "myImageView.h"
#implementation myImageView
#synthesize imageName;
- (id)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
if (self) {
// Initialization code
}
return self;
}
#end
then use a dictionary to keep everything instead of array + dictionary.
myImageView *imgView1 = [[myImageView alloc] init];
[imgView1 setImageName:#"image_name_here"];
[imgView1 setImage:[UIImage imageNamed:#"image_name_here"]];
NSMutableDictionary *dicti = [[NSMutableDictionary alloc] init];
[dicti setObject:imgView1 forKey:#"image_name_here_1"];
[dicti setObject:imgView2 forKey:#"image_name_here_2"];
[dicti setObject:imgView... forKey:#"image_name_here_..."];
when you find the imageView you can search image in dictionary. because you know name of the imageView now.
I am trying to place an image one after another using GCD like following
-(void)setUpImages {
NSArray *images = #[[UIImage imageNamed:#"blogger-icon.png"],
[UIImage imageNamed:#"gplus-icon.png"],
[UIImage imageNamed:#"facebok-icon.png"]
];
[images enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
dispatch_sync(dispatch_get_main_queue(), ^{
UIImageView *imageView = [[UIImageView alloc] initWithFrame:CGRectMake(80, idx * ((UIImage*)obj).size.height + idx*30 + 10, ((UIImage*)obj).size.width, ((UIImage*)obj).size.height)];
NSLog(#"index is %#",NSStringFromCGRect(imageView.frame));
[imageView setImage:(UIImage*)obj];
[self.view.layer addSublayer:imageView.layer];
sleep(1);
});
}];
}
I am using dispatch_sync because I want it will wait until its block is done ( first image is placed on the screen) then second images will be and so the third one does. And all thing are happening on the main thread now.
However, it seems I am getting a deadlock in the middle and my logic is wrong at some points.
I need help to understand this situation. Please help.
From the documentation of dispatch_sync:
Calling this function and targeting the current queue results in deadlock.
That said, I think you have a design problem and you can achieve the desired result without involving GCD.
Since it looks like you want to update the UI every k seconds, avoid using sleep(1) and invoke a method recursively with a delay using performSelector:withObject:afterDelay:.
Something like
- (void)updateImageViewWithImageAtIndex:(NSNumber *)i {
UIImage * image = self.images[i.intValue];
UIImageView * imageView = [[UIImageView alloc] initWithFrame:CGRectMake(80, idx * image.size.height + idx*30 + 10, image.size.width, image.size.height)];
NSLog(#"index is %#",NSStringFromCGRect(imageView.frame));
[imageView setImage:image];
[self.view.layer addSublayer:imageView.layer];
if (i < images.count - 1) {
[self performSelector:#selector(updateImageViewWithImageAtIndex:) withObject:#(i.intValue++) afterDelay:1];
}
}
- (void)setUpImages {
// Assuming you have declared images as a property
self.images = #[[UIImage imageNamed:#"blogger-icon.png"],
[UIImage imageNamed:#"gplus-icon.png"],
[UIImage imageNamed:#"facebok-icon.png"]
];
[self updateImageViewFromImages:images index:0];
}
Now I may be completely wrong here, but it looks like all you're trying to do is change the image in an image view once a second, in which case your approach is incorrect. UIImageView has methods for this built in. For example:
NSArray *images = #[[UIImage imageNamed:#"blogger-icon.png"],
[UIImage imageNamed:#"gplus-icon.png"],
[UIImage imageNamed:#"facebok-icon.png"]
];
UIImageView *imageView = [[UIImageView alloc] initWithFrame:CGRectMake(80, idx * ((UIImage*)obj).size.height + idx*30 + 10, ((UIImage*)obj).size.width, ((UIImage*)obj).size.height)];
[imageView setAnimationDuration:3];
[imageView setAnimationImages:images];
[imageView startAnimating];
I think Gabriele nailed the deadlock above. Don't call dispatch_sync and pass in the main queue.
Another possible problem: I suspect that manipulating a layer's views is not thread-safe. It shouldn't cause a deadlock, but it could cause undesirable consequences.
I've implemented a scrollview with paging to scroll between some images (graphs) at full page (like the Photo app installed in the iPhone).
I found the code below that use the classical 3 pages solution (I made some small modification for my application) but, even if it "works", the scrolling seems to be slow and often after I've scrolled some images the application crashes.
I'm using Xcode 4.2 with ARC option enabled and testing both on an iPad device.
Images (10 jpg) are 2048x1539 with a mean dimension of 200/250Kb each.
Is there anyone that can help me in finding the cause of the problem ?
Thanks,
Corrado
const int numImages = 10;
const float kPageWidth = 1024.0f;
const float kPageHeight = 768.0f;
- (void)viewDidLoad {
[super viewDidLoad];
scroll.contentSize = CGSizeMake(kPageWidth * numImages, kPageHeight);
imageview1 = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, kPageWidth, kPageHeight)];
imageview2 = [[UIImageView alloc] initWithFrame:CGRectMake(kPageWidth, 0, kPageWidth, kPageHeight)];
imageview3 = [[UIImageView alloc] initWithFrame:CGRectMake(kPageWidth * 2, 0, kPageWidth, kPageHeight)];
scroll.contentOffset = CGPointMake(0, 0);
[imageview1 setImage:[UIImage imageNamed:#"grafico_0.jpg"]];
imageview1.contentMode = UIViewContentModeScaleAspectFit;
[imageview1 setTag:1];
imageview2.contentMode = UIViewContentModeScaleAspectFit;
[imageview2 setTag:2];
imageview3.contentMode = UIViewContentModeScaleAspectFit;
[imageview3 setTag:3];
[scroll addSubview:imageview1];
[scroll addSubview:imageview2];
[scroll addSubview:imageview3];
}
- (void)scrollViewDidScroll:(UIScrollView*)scrollView {
const CGFloat currPos = scrollView.contentOffset.x;
const NSInteger selectedPage = lroundf(currPos * (1.0f / kPageWidth));
const NSInteger zone = 1 + (selectedPage % 3);
const NSInteger nextPage = selectedPage + 1;
const NSInteger prevPage = selectedPage - 1;
/// Next page
if (nextPage < numImages)
{
NSInteger nextViewTag = zone + 1;
if (nextViewTag == 4)
nextViewTag = 1;
UIImageView* nextView = (UIImageView*)[scrollView viewWithTag:nextViewTag];
nextView.frame = (CGRect){.origin.x = nextPage * kPageHeight, .origin.y = 0.0f, kPageHeight, kPageWidth};
NSString *str = [NSString stringWithFormat:#"grafico_%d.jpg", nextPage];
UIImage* img = [UIImage imageNamed:str];
nextView.image = img;
}
/// Prev page
if (prevPage >= 0)
{
NSInteger prevViewTag = zone - 1;
if (!prevViewTag)
prevViewTag = 3;
UIImageView* prevView = (UIImageView*)[scrollView viewWithTag:prevViewTag];
prevView.frame = (CGRect){.origin.x = prevPage * kPageHeight, .origin.y = 0.0f, kPageHeight, kPageWidth};
NSString *str = [NSString stringWithFormat:#"grafico_%d.jpg", prevPage];
UIImage* img = [UIImage imageNamed:str];
prevView.image = img;
}
}
You should not use imageNamed: for the loading of your large images, because that method caches the images and should only be used for small images that you use multiple times in your App (like images for buttons etc.). That method is notorious for causing memory problems when used with many large images.
Switch to imageWithContentsOfFile: instead. Loading your images with that methods secures that the images are not cached and the memory is freed after you do not use that images any more.
If the scrolling seems to be sluggish you can move the loading of the image to a background thread using performSelectorInBackground:
[self performSelectorInBackground:#selector(retrieveImageData:) withObject:imagePath];
the loading of the UIImage happens in this method:
- (void)retrieveImageData:(NSString *)imagePath {
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
UIImage *image = [UIImage imageWithContentsOfFile:imagePath];
[self performSelectorOnMainThread:#selector(imageDataRetrieved:) withObject:image waitUntilDone:NO];
[pool release];
}
and the attachment of the image to the UIImageView on the main thread (UI manipulations must not happen on a background Thread):
- (void)imageDataRetrieved:(UIImage)*image {
yourImageView.image = image;
}