what is the best method to display about 300 png images into a UITableView..
i dont wanna display them at the same time... i have 3 tableViewControllers that will each display about 100 imgaes.. (its for a catalog so the images are important to display)
i used [uiimage imageNamed:] but that method caches the images and they dont get released so the memory usage is big.... is there any way to release the cache when the nav controller pushes a different view controller?
i also tried [uiimage alloc] initWithContentsOfFile] but the images wont display....
any help?
[UIImage imageNamed:#"foo.png"];
is equivalent to
[[[UIImage alloc] initWithContentsOfFile:[[NSBundle mainBundle] pathForResource:#"foo" ofType:#"png"]] autorelease];
except it does not cache the image.
If you write your own caching function, you can purge it at any time. When you need an image, check an NSMutableDictionary by name. If it does not exist, load the image normally and add it to the dictionary with the name as a key. To flush the cache, remove all objects from the dictionary.
Related
Hi every one I have the next issue I'm creating various images like this
UIImage *image = [UIImage imageNamed:_imageName];
and I'm assigning to one UIImageView
[self.imgvImage setImage:image];
The user when tap a button one UIImageView is created and one UIImage is assigning, I have 4 UIImageViews created when new is created the last is removed sending release to the UIImageView like this
[_imgvImage release];
But around than 100 times creating and releasing one memory warring happen but the app dont crash I think this is because the UIImages created are not releasing and there are so much because all the code are clean and creating and releasing are all fine.
How can I remove all the UIIMageView with his UIImage completely from the memory.
Please help, sorry for my English in not good.
The image created using below statement is handled by iOS. this image is stored in a cache so that next time you call this it is simply get returned from the cache.
UIImage *image = [UIImage imageNamed:_imageName];
I think you should not worry about memory warning as long as you are releasing what you are allocating (UIImageView in this case). iOS should clear this cache in case of memory crunch.
If you do not want that caching (e.g. when you are loading one image once only) you can use imageWithContentsOfFile: method of UIImage.
Hi I found the solution the solution was call the
NSAutoreleasePool
in the method when I removed the objects of the view like this:
for(ProductVW *pVW in [_vwProductsContainer subviews]){
NSAutoreleasePool * autoreleasePool = [[NSAutoreleasePool alloc] init];
[pVW removeFromSuperview];
[autoreleasePool release];
}
I am loading image with data in my table view. Images are coming from web. I created method to get image url in model class.Model class has Nsdictionary and objects.
But this images is slowing down scrolling .Here is my code
UIImage *image = [UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:[NSString stringWithFormat:#"%#",
[(Tweet *)[recentTweets objectAtIndex:indexPath.row]urlString]]]]];
cell.imageView.image = image;
Please tell Where I am going wrong?
Use lazy loading and do your own drawing. Try to understand the techniques on the sample projects I linked. These are the best ways to improve the performance of tables with images.
here is the methodology I use for loading images into a UITableView from a remote location:
in your .h file, declare a mutable dictionary for storing the images:
NSMutableDictionary *images;
initialize the dictionary in -init... or in -viewDidLoad
images = [[NSMutableDictionary alloc]init];
in the .m, tableView:cellForRowAtIndexPath:, see if the image exists in your dictionary for the indexPath
UIImage *img = [images objectForKey: indexPath];
if the image does exist, just set it.
if (img) cell.imageView.image = img;
if the image does NOT exist, set the cell's image to a temporary image...
if (!img) cell.imageView.image = [UIImage imageNamed:#"imageUnavailable.png"];
AND add that image to your dictionary so it doesnt try to refetch the image if you scroll off and back to that image before it loads...
[images setObject:[UIImage imageNamed:#"imageUnvailable.png"] forKey: indexPath];
then, in this same block, use an NSOperationQueue, and a custom NSOperation ( here is a reference - NSOperation and SetImage) to get your image and call back into your UITableViewController with that image.
in your callback, add your image to the dictionary (overwriting the temp image) and call [tableView reloadData]
this will give you a nice non blocking user experience.
The are a couple of ways how to do it. I had the best experience with a Queue for the HttpRequests, which I pause during the scrolling process.
I highly recommend this framework for that:
http://allseeing-i.com/ASIHTTPRequest/
I also implemented an image cache, which only loads the images if there weren't in the cache.
And the last tweak was to actually draw the images instead of using a high level uicomponent like the UIImageView
The number one reason your code is slow right now is because you're making a network call on the main thread. This blocks an UI from being updated and prevents the OS from handling events (such as taps).
As already suggested, I recommend ASIHTTPRequest. Combine asynchronous requests with an NSOperationQueue with a smaller concurrency count (say, 2) for the image requests, caching, and reloading the rows when images come in (on the main thread) (also only reloading the row if its currently visible). You can get a smooth scrolling table view.
I have an example of this on github here: https://github.com/subdigital/iphonedevcon-boston
It's in the Effective Network Programming project and includes a set of projects that progressively improve the experience.
Download the images before you load the tableView, and store them in an NSArray. Then when the cellForRowAtIndexPath method is called, show a loading image until the image is in the array.
I'm able to pull information from a plist using:
nameTextField.text = [recipe objectForKey:NAME_KEY];
ingredientsText.text = [ingredients objectForKey:NAME_KEY];
I also have images in the plist [the names of the images, not the image data]
does anyone know how i would display an image in a similar manner?
thanks in advance.
You'll have to create an image with the contents of the file at the stored path. Either use imageWithContentsOfFile: or imageNamed:, where imageNamed: takes only the filename and caches images, useful for images that are small and appear often in the UI. Also note, that imageNamed: searches for a #2x-Version of the image in iOS4.
imageWithContentsOfFile takes a full path including your app-bundle's path and dose not have a cache. It's intended for larger images that only appear once on a screen.
imageView.image = [UIImage imageNamed:[recipe objectForKey:IMAGE_KEY]];
imageView.image = [UIImage imageWithContentsOfFile:[[NSBundle mainBundle]
pathForResource:[recipe objectForKey:IMAGE_KEY] ofType:nil]];
I need a clarification from all of you,That is I am implementing an iPad application. In that I tried to download and animate the images. The image count should be more than 100,000.The code I used to download and adding to the view is as follows.
UIImageView* imageView=[[UIImageView alloc]initWithFrame:CGRectMake(0, 0,100,100)];
NSData *receivedData=nil;
receivedData = [NSData dataWithContentsOfURL:[NSURL URLWithString:#"http://path/prudently/iphone/image_s/e545afbf-4e3e-442e-92f9-a7891fc3ea9f/test.png"]];
imageView.image = [[UIImage alloc] initWithData:receivedData] ;
[subView addSubview:imageView];
[imageView release];
But I am getting exception after I successfully added more than 8000 image to my subview. I am getting exception at getting data from the url. And one more thing I am not releasing the subview because once I downloaded them I need to animate the subview.
Please give me your suggessions
Thank you,
Sekhar Bethalam.
100,000 images would seem a lot for desktop applications, let alone a smart phone like an iPhone. Is there not another approach you can take to solve this problem that wouldn't need such a high resource count?
You can write the URL , images or something to a cached file, and divide some pages to animate the images...
When the user press a page link , application read and animate the images of this page, images of the page which user don't use need not display.
The only way you are going to accomplish this is to dynamically create and destroy the UIImageViews as they are needed on the screen. The iPhone/iPad/iAnything are incapable of doing what you want because of the limited memory available on the device.
I'm using the following code:
UIImage *buttonImage;
if (p.placeImage != nil) {
buttonImage = [UIImage imageWithData:p.placeImage];
} else {
buttonImage = [UIImage imageNamed:#"bg_place_noimg.png"];
}
[imageButton setBackgroundImage:buttonImage forState:UIControlStateNormal];
When executing the app with Instruments I can see the setBackgroundImage consumes a lot of memory. However, if I comment the last line it doesn't happen. Any possible reason?
EDIT:
If p.placeImage == nil and imageNamed:#"bg_place_noimg.png" is used memory usage is normal. p.placeImage is a Transformable value I use in Core Data to store images NSData downloaded from Internet.
I'm not surprised that commenting out the last line causes less memory to be consumed. When you set that image as the background of your button, the image is most likely retained by the button and so the image remains in memory. If you don't apply the image as the button background, the UIImage's retain count is 0 and so its memory can be reclaimed by the system if necessary.
Kristopher's theory about the difference between imageWithData and imageNamed is also correct. Check out the Discussion section for each of those initializers in the documentation for UIImage.
I'm not sure, but I would guess that your problem is that imageWithData: creates a whole new image each time, whereas the imageNamed: method returns the same image over and over again.
You may need to add some code to cache and reuse images that are identical. For example, maybe you could use a URL as a key into a dictionary of images, and only create new images for URLs that have not been loaded before.