I am creating many UIImageview using for loop like a wallpaper app. And i am adding UIActivityIndicatorView to each UIImageview. UIImageview load image from the webservice. when the image is loaded to the UIImageview that time the UIActivityIndicatorView of this UIImageview is hide.
I am give tag of both UIImageview and UIActivityIndicatorView.
Please tell me how do this.
Just use a completion block for the image fetching.
dispatch_queue_t q = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0);
dispatch_async(q, ^{
// Fetch the image from the server
NSData *data = [NSData dataWithContentsOfURL:url];
UIImage *img = [[UIImage alloc] initWithData:data];
// Add activity indicatory to image view
[imageview addSubview:activityIndicator];
dispatch_async(dispatch_get_main_queue(), ^{
imageview.image = img;
// After finishing image loading remove activity indicator
[activityIndicator stopAnimating];
[activityIndicator removeFromSuperview];
});
});
if you have a reference to an instance of UIActivityIndicatorView, just remove it from superView:
[activityIndicator stopAnimating];
[activityIndicator removeFromSuperview];
Related
I have a UICollectionView displaying a bunch of images. If I don't load the images asynchronously the scrolling is very choppy and provides a poor user experience. When I load the images asynchronously the scrolling is smooth but it takes a good 5 to 10 seconds to load each image.
Why does it take so long for images to appear when loaded in the background? Here is my code for the background thread which is inside of the cellForItemAtIndexPath delegate:
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
UIImageView *bg = (id)self.backgroundView;
UIImageView *selbg = (id)self.selectedBackgroundView;
if (![bg isKindOfClass:[UIImageView class]])
bg = [[UIImageView alloc] initWithImage:thumb];
else
[bg setImage:thumb];
if (![selbg isKindOfClass:[UIImageView class]]){
selbg = [[UIImageView alloc] initWithImage:thumb];
coloroverlay = [[UIView alloc] initWithFrame:selbg.bounds];
[coloroverlay setAutoresizingMask:UIViewAutoresizingFlexibleWidth|UIViewAutoresizingFlexibleHeight];
[selbg addSubview:coloroverlay];
} else
[selbg setImage:thumb];
[bg setContentMode:UIViewContentModeScaleAspectFill];
[bg setTag: 1];
[coloroverlay setBackgroundColor:[col colorWithAlphaComponent:0.33f]];
[selbg setContentMode:UIViewContentModeScaleAspectFill];
dispatch_sync(dispatch_get_main_queue(), ^{
[self setBackgroundView:bg];
[self setSelectedBackgroundView:selbg];
});
});
EDIT: As #geraldWilliam pointed out, I shouldn't be accessing views from the secondary thread. Here is what I have updated my code to and fixed the issue of images getting set to the wrong cell:
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
UIImageView *bg = (id)self.backgroundView;
UIImageView *selbg = (id)self.selectedBackgroundView;
if (![bg isKindOfClass:[UIImageView class]]) bg = [[UIImageView alloc] initWithImage:thumb];
if (![selbg isKindOfClass:[UIImageView class]]){
selbg = [[UIImageView alloc] initWithImage:thumb];
coloroverlay = [[UIView alloc] initWithFrame:selbg.bounds];
[coloroverlay setAutoresizingMask:UIViewAutoresizingFlexibleWidth|UIViewAutoresizingFlexibleHeight];
[selbg addSubview:coloroverlay];
}
dispatch_sync(dispatch_get_main_queue(), ^{
[bg setImage:thumb];
[selbg setImage:thumb];
[bg setContentMode:UIViewContentModeScaleAspectFill];
[bg setTag: 1];
[coloroverlay setBackgroundColor:[col colorWithAlphaComponent:0.33f]];
[selbg setContentMode:UIViewContentModeScaleAspectFill];
[self setBackgroundView:bg];
[self setSelectedBackgroundView:selbg];
});
});
Most of the code you have here is fine for the main queue. The loading of the image should be on a global queue, but the rest, especially setting the image view's image, should be on the main queue. What's going on in your code is that you're dispatching back to the main queue to set the background view but leaving the assignment of the image property in the background. So, try something like:
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
UIImage *image = [UIImage imageWithData:[NSData dataWithContentsOfURL:myImageURL]];
dispatch_sync(dispatch_get_main_queue(), ^{
imageView.image = image;
[self setBackgroundView:imageView];
});
});
I strongly recommend watching WWDC 2012 Session 211: Building Concurrent User Interfaces on iOS, which is the best WWDC session ever. It’s full of clearly presented, practical advice.
Doing stuff with UIImageView off the main queue is worrying and should be fixed, but is probably not the cause of slowness. You haven’t showed us where thumb comes from, which is likely the slow bit.
I have created collection view programmatically where i have created UIImageview programmatically within collectionViewCell and images are displayed in imageview are downloaded from server asynchronously.
Code below is written in cellForItemAtIndexPath: method -
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0), ^{
NSURL *imageURL = [NSURL URLWithString:[arrmImgPaths objectAtIndex:indexPath.row]];
NSData *imageData = [NSData dataWithContentsOfURL:imageURL];
UIImage *image = [UIImage imageWithData:imageData];
// [imgvMainView removeFromSuperview];
// Now the image will have been loaded and decoded and is ready to rock for the main thread
dispatch_sync(dispatch_get_main_queue(), ^{
imgvMainView =[[UIImageView alloc] initWithFrame:CGRectMake(34,41,177,124)];
[cell addSubview:imgvMainView];
[imgvMainView setImage:image];
imgvMainView.contentMode = UIViewContentModeScaleAspectFit;
});
});
Problem is, when i scroll collection view some images are overlapped on one another. Please tell me solution to avoid it.
Thanks in advance.
Please use below line I hope this would work what I am assuming problem of duplicate cell.
UIImageView* imgvMainView =[[UIImageView alloc] initWithFrame:CGRectMake(34,41,177,124)];
[cell.contentView addSubview:imgvMainView];
This is most likely happening because you are reusing cells (correctly) and that the previous use of the cell is still calling the previous image. You must cancel the async task when the cell goes out of view. By the way, it will make you life much easier to use AFNetworking+UIImageView to do this.
One other option is to check that there is no UIimageView in your cell before you create one.
dispatch_sync(dispatch_get_main_queue(), ^{
UIView *viewToRemove;
for (UIView *view in cell.subViews) {
if (view isKingOfClass:UIImageView){
viewToRemove = view;
}
}
[viewToRemove removeFromSuperView];
imgvMainView =[[UIImageView alloc] initWithFrame:CGRectMake(34,41,177,124)];
[cell addSubview:imgvMainView];
[imgvMainView setImage:image];
imgvMainView.contentMode = UIViewContentModeScaleAspectFit;
});
I have a "loading" view added to an uiimageview to indicate the image is being loaded, then on a dispatch async I am charging the image and removing the "loading" view once it has finished, problem is that if I call twice this method the "loading" view is added twice and the second one is never removed.
Edited:
on view.h
UIView *loading;
on view.m
loading = [[UIView alloc]initWithFrame:CGRectMake(0, 0, 100, 100)];
loading.backgroundColor = [UIColor blackColor];
loading.alpha = 0.8;
loading.layer.cornerRadius = 10;
loading.center = CGPointMake(imageView.frame.size.width/2, imageView.frame.size.height/2);
if (![imageView.subviews containsObject:loading]) {
[imageView addSubview:loading];
}
dispatch_queue_t downloadFoto = dispatch_queue_create("Get Photo", NULL);
dispatch_async(downloadFoto, ^{
UIImage *image = [[UIImage alloc]initWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:[selectedImage objectForKey:#"url"]]]];
dispatch_sync(dispatch_get_main_queue(), ^{
if (image) {
[imageView setImage:image];
[imageView setNeedsLayout];
if ([imageView.subviews containsObject:loading]) {
[loading removeFromSuperview];
}
}
});
});
If this is called just once or if I call it after the loading is already removed everything works fine, the problem is if I call this before the block had finished.
Thank you guys, this is my solution at the end.
if (!blackView) {
UIActivityIndicatorView *load = [[UIActivityIndicatorView alloc]initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhiteLarge];
blackView = [[UIView alloc]initWithFrame:CGRectMake(0, 0, 100, 100)];
blackView.backgroundColor = [UIColor blackColor];
blackView.alpha = 0.8;
blackView.layer.cornerRadius = 10;
blackView.center = CGPointMake(fotoVisual.frame.size.width/2, fotoVisual.frame.size.height/2);
load.center = CGPointMake(blackView.frame.size.width/2, blackView.frame.size.height/2);
[load startAnimating];
[blackView addSubview:load];
[fotoVisual setImage:[UIImage imageNamed:#"previewImagen.png"]];
descripcionFotoView.text = [selectedImage objectForKey:#"titulo"];
}
if (![fotoVisual.subviews containsObject:blackView]) {
[fotoVisual addSubview:blackView];
}
dispatch_queue_t downloadFoto = dispatch_queue_create("Get Photo", NULL);
dispatch_async(downloadFoto, ^{
[fotoVisual setImageWithURL:[NSURL URLWithString:[selectedImage objectForKey:#"url"]]
placeholderImage:[UIImage imageNamed:#"previewImagen.png"]];
dispatch_async(dispatch_get_main_queue(), ^{
[blackView removeFromSuperview];
blackView = nil;
});
});
dispatch_release(downloadFoto);
It looks like the issue you have is that you are creating a new loading view each time, which is not what you want. Your [imageView.subviews containsObject:loading] will never be true as you make a new loading view each time.
You could change the creation logic to do the checking like this
if (!loading) {
// configure loading
[imageView addSubview:loading];
}
Then modify your call back to something like
dispatch_sync(dispatch_get_main_queue(), ^{
if (image) {
[imageView setImage:image];
[imageView setNeedsLayout];
[loading removeFromSuperview];
loading = nil;
}
});
Is there any specific reason you are using dispatch_sync instead of dispatch_async?
Add you loading subview in dispatch_async block
dispatch_queue_t downloadFoto = dispatch_queue_create("Get Photo", NULL);
dispatch_async(downloadFoto, ^{
if (!loading.superview) {
// we assume your loading view doesn't have a superview so we can add it to imageView
dispatch_sync(dispatch_get_main_queue(), ^{
[imageView addSubview:loading];
};
}
UIImage *image = [[UIImage alloc]initWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:[selectedImage objectForKey:#"url"]]]];
if (image) {
dispatch_sync(dispatch_get_main_queue(), ^{
[imageView setImage:image];
[imageView setNeedsLayout];
if ([imageView.subviews containsObject:loading]) {
[loading removeFromSuperview];
}
});
}
});
For Async image downloading you can also use SDWebimage
Just download the project and add SDWebimage folder to your project and use as folows
#import "UIImageView+WebCache.h"
[self.imageView setImageWithURL:[NSURL URLWithString:[selectedImage objectForKey:#"url"]]
placeholderImage:[UIImage imageNamed:#"placeholder.png"]];
This will also cache the image.
When moving from one view to another, I want in my second view as long as the image is being downloaded to see a spinner (so that the second view will open instantly not take any time at all, and the user waits for the spinner to finish).
Here is my code:
In the second View, the one that opens:
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view.
UIActivityIndicatorView *spinner=[[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleGray];
spinner.center=CGPointMake(160.0,240.0 );
spinner.hidesWhenStopped=YES;
[self.view addSubview:spinner];
[spinner startAnimating];
NSString *urlString=[NSString stringWithFormat:#"http://mysite.com/projects/test/test.jpg"];
NSLog(#"URL is:%#",urlString);
NSURL *url=[NSURL URLWithString:urlString];
[more_info_image setImage:[UIImage imageWithData:[NSData dataWithContentsOfURL:url]]];
[spinner stopAnimating];
}
I do not see the spinner at all. i do not think that this is because my internet connection is so fat. On the other hand, I see a little delay when a button is pressed and waiting for the view to open - like that it is that time when it tries to download the image.
I want to open the view, have the spinner, download the image and then let the spinner go away.
Must I change anything?
You might not be seeing the UIActivityIndicatorView since you are using [NSData dataWithContentsOfURL:url] on the main thread. This is blocking the main thread from displaying the UIActivityIndicatorView until after the image is downloaded, and by that point you are removing it.
You might want to do something like:
but make sure you define spinner in your *.h file for this to work.
- (void)viewDidLoad
{
...
//This code will make downloadImage run in the background thread
[self performSelectorInBackground:#(downloadImage) withObject:nil]
...
}
- (void) downloadImage{
NSLog(#"URL is:%#",urlString);
NSURL *url=[NSURL URLWithString:urlString];
UIImage *downloadedImage = [UIImage imageWithData:[NSData dataWithContentsOfURL:url]];
//This code will make setImage run in the main thread since it is changing UI
[more_info_image performSelectorOnMainThread:#selector(setImage:) withObject:downloadedImage waitUntilDone:NO];
//This code will make stopAnimating run in the main thread since it is changing UI
[spinner performSelectorOnMainThread:#selector(stopAnimating) withObject:nil waitUntilDone:NO];
}
The other way is to use Grand Central Dispatch and do something like:
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view.
UIActivityIndicatorView *spinner=[[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleGray];
spinner.center=CGPointMake(160.0,240.0 );
spinner.hidesWhenStopped=YES;
[self.view addSubview:spinner];
[spinner startAnimating];
//This is the new GCD code
dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0ul);
dispatch_async(queue, ^{
//This code will run on a background thread
NSString *urlString=[NSString stringWithFormat:#"http://mysite.com/projects/test/test.jpg"];
NSLog(#"URL is:%#",urlString);
NSURL *url=[NSURL URLWithString:urlString];
UIImage *downloadedImage = [UIImage imageWithData:[NSData dataWithContentsOfURL:url]];
dispatch_sync(dispatch_get_main_queue(), ^{
//this code runs on the main thread since it is UI changes
[more_info_image setImage:downloadedImage];
[spinner stopAnimating];
});
});
}
As you are downloading your image in the viewDidLoad method so while the image is downloading it did not loads your view so that's why you are experiencing a delay try this
in your header file add an instance of UIActivityIndicator
UIActivityIndicator *spinner;
in your implementation file do something like this
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view.
spinner=[[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleGray];
spinner.center=CGPointMake(160.0,240.0 );
spinner.hidesWhenStopped=YES;
[self.view addSubview:spinner];
[spinner startAnimating];
[self performSelector:#selector(downloadYourImageMethod) withObject:nil afterDelay:1];
}
-(void)downloadYourImageMethod
{
NSString *urlString=[NSString stringWithFormat:#"http://mysite.com/projects/test/test.jpg"];
NSURL *url=[NSURL URLWithString:urlString];
[myIMageview setImage:[UIImage imageWithData:[NSData dataWithContentsOfURL:url]]];
[spinner stopAnimating];
}
modify your code as
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view.
UIActivityIndicatorView *spinner=[[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleGray];
spinner.center=CGPointMake(160.0,240.0 );
spinner.hidesWhenStopped=YES;
[self.view addSubview:spinner];
[spinner startAnimating];
[self performSelector:#selector(downloadImage) withObject:nil afterDelay:0.1];
}
-(void)downloadImage
{
NSString *urlString=[NSString stringWithFormat:#"http://mysite.com/projects/test/test.jpg"];
NSLog(#"URL is:%#",urlString);
NSURL *url=[NSURL URLWithString:urlString];
[more_info_image setImage:[UIImage imageWithData:[NSData dataWithContentsOfURL:url]]];
[spinner stopAnimating];
}
Sometimes, it all depends on how you are placing your views. The spinner should the very last thing that's added to the hierarchy in order to be the first in the order when your view loads. This was the issue in my case, I hope this help anyone else that bumps into this answer. :)
I'm trying to load images in the background using gcd. My first attempt didn't work:
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_LOW,0), ^{
dispatch_async(dispatch_get_main_queue(), ^{
// create UI Image, add to subview
});
});
commenting out the background queue code and leaving just the main queue dispatch block didn't work:
dispatch_async(dispatch_get_main_queue(), ^{
// create UI Image, add to subview
});
Is there some trick to doing ui stuff inside a gcd block?
In response to mattjgalloway's comment, I'm simply trying to load a big image in a background thread. Here's the full code that I tried originally:
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_LOW,0), ^{
UIImage* img = [[UIImage alloc] initWithContentsOfFile: path];
dispatch_async(dispatch_get_main_queue(), ^{
imageView = [[[UIImageView alloc] initWithImage: img] autorelease];
imageView.contentMode = UIViewContentModeScaleAspectFill;
CGRect photoFrame = self.frame;
imageView.frame = photoFrame;
[self addSubview:imageView];
});
});
I simplified it so that I was running everything inside the main queue, but even then it didn't work. I figure if I can't get the whole thing to work in the main queue, no way the background queue stuff will work.
================ UPDATE ==============
I tried the above technique (gcd and all) in a brand new project and it does indeed work as expected. Just not in my current project. So I'll have to do some slow, painful process of elimination work to figure out what's going wrong. I'm using this background loading to display images in a uiscrollview. Turns out bits of the images do sometimes show up, but not always. I'll get to the bottom of this....
================ UPDATE ==============
Looks like the issue is related to the UIScrollView all of this is inside. I think stuff isn't getting drawn/refreshed when it should
I ran your code. It works with one exception. Also did you mean self.view rather than self?
Case 1:
path is declared at a property.
imageView is declared at an ivar
- (IBAction)buttonImagePressed:(id)sender
{
self.path = [[[NSBundle mainBundle] resourcePath] stringByAppendingPathComponent:#"picture1.jpg"];
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_LOW,0), ^{
UIImage* img = [[UIImage alloc] initWithContentsOfFile: self.path];
dispatch_async(dispatch_get_main_queue(), ^{
imageView = [[[UIImageView alloc] initWithImage: img] autorelease];
imageView.contentMode = UIViewContentModeScaleAspectFill;
CGRect photoFrame = self.view.frame;
imageView.frame = photoFrame;
[self.view addSubview:imageView];
});
});
}
Case 2:
path and imageView are both ivars. - no property is used.
- (IBAction)buttonImagePressed:(id)sender
{
// will crash if path is defined here
// path = [[[NSBundle mainBundle] resourcePath] stringByAppendingPathComponent:#"picture1.jpg"];
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_LOW,0), ^{
//if path is defined here then it will work
path = [[[NSBundle mainBundle] resourcePath] stringByAppendingPathComponent:#"picture1.jpg"];
UIImage* img = [[UIImage alloc] initWithContentsOfFile:path];
dispatch_async(dispatch_get_main_queue(), ^{
imageView = [[[UIImageView alloc] initWithImage: img] autorelease];
imageView.contentMode = UIViewContentModeScaleAspectFill;
CGRect photoFrame = self.view.frame;
imageView.frame = photoFrame;
[self.view addSubview:imageView];
});
});
}
On case 2, where it crashed, the message in the console said to file a bug at apple.com ...
Try to call setNeedDisplay right after [self addSubview:imageView], by the way most of UIKit isn't thread safe, I don't know about UIImage methods specifically (maybe is ok on iOS4 and higher), but I wouldn't do that. If you want to load images from background better use ImageIO that is thread safe, or Core Graphics functions.
An alternative could be load an NSData object with your image data on a background thread an later call [UIImage alloc]inithWithData: data] on the main thread.
Displaying my image as a background image, rather than a UIImageView added as a subview works. No clue why
#interface PhotoView(){
UIImageView* imageView;
}
#end
#implementation PhotoView
-(id)initWithFrame:(CGRect)frame andPathToPhoto:(NSString*)path andSequenceView:(SequencerView*) sequencerView{
if(self = [super initWithFrame:frame]){
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_LOW,0), ^{
UIImage* img = [[UIImage alloc] initWithContentsOfFile: path];
dispatch_async(dispatch_get_main_queue(), ^{
self.backgroundColor = [UIColor colorWithPatternImage:img];
});
[img release];
});
}
return self;
}
#end