Async load multiple images to single cell - ios

I have a problem with loading of 5 images to each cell of TableView. I use AFNetworking for download and setImageWithUrl method for imageView:
for (int i = 0; i < urls.count; i++) {
[self.photoImageView[i] setImageWithURL:urls[i]];
}
TableView very brakes when I scroll it. But when i try to load 1 or 2 no brakes when scrolling.
How to correct download images without brakes?

I think's it's helpful for you below the code work for me.
First fall you use this library SDWebImage
then implement below code.
#import <SDWebImage/UIImageView+WebCache.h>
...
[cell.imageView sd_setImageWithURL:[NSURL URLWithString:#"URL"]
placeholderImage:[UIImage imageNamed:#"placeholder.png"]];

You can use SDWebImage as discussed by #Ravi. You can use use the above code in your for loop to display all 5 images asynchronously , without blocking main thread.
for (int i = 0; i < urls.count; i++) {
[self.photoImageView[i] sd_setImageWithURL:[NSURL URLWithString:urls[i]]
placeholderImage:[UIImage imageNamed:#"placeholder.png"]];
}
If you dont want to use any third party libraries, you can also use GCD for the same. Check this ans.
Hope it helps. Happy Coding!!

If you see UIImage + AFNetworking class,It internally loads image using Async NSOperations.Try loading image with specific dimensions.It will download image of that size & could improve scrolling performance.
NSMutableString *newURLPath = [NSMutableString stringWithString[exercise.imageURL absoluteString]];
[newURLPath appendFormat:#"?width=200&"];
[newURLPath appendFormat:#"height=200"];

For downloading the Asynchronous image from url, use any of these library for improving the scroll performance
SDWebImage - Asynchronous image downloader with cache support as a UIImageView category.
#import <SDWebImage/UIImageView+WebCache.h>
...
[imageView sd_setImageWithURL:URL
placeholderImage:[UIImage imageNamed:#"placeholder.png"]
];
PINRemoteImage - It download a progressive jpeg and get attractive blurred updates.
For in your case, you can go for SDWebImage.
For Advance Concept, you could look into this one.
AsyncDisplayKit - Smooth asynchronous user interfaces for iOS apps
Even recently, Pinterest was built on top of AsyncDisplayKit to Keeps UIs smooth and responsive.
Read this article for more info: https://medium.com/#Pinterest_Engineering/re-architecting-pinterest-039-s-ios-app-e0a2d34a6ac2

Related

How to put my url images into carousel?

I am getting URL images from API. I have stored the UR images into string. Here my problem I want to display that into carousel. I don't know how to do this. Below is my code that I have tried.
for(int i=0;i<hotelIMAges.count;i++ )
{
NSDictionary *images=[hotelIMAges objectAtIndex:i];
NSString *Images= [images objectForKey:#"Imagepath"];
[ImageARRAy addObject:Images];
} //Here I have stored all the images into string..(https://***.jpg)
Carousel *carousel = [[Carousel alloc] initWithFrame:CGRectMake(0, 0,300, 262)];
[carousel setImages:ImagesARRAy];
You just need to process asynchronously as your current approach can be a synchronous request and blocks the main thread until that download is complete.
Consider using SDWebImage and the UIImageView extension it adds to manage the image download and display. It also supports a placeholder image that you can supply to indicate that the download is in progress.
If your using any third party carousel check for asynchronous methods to display the images.I believe setImages: method must be for images that are stored locally inside app. Do let me know if you have any queries.
----EDITED----
Your Carousel is using synchronous method to display which blocks the main thread.
You can use SDWebImage for your purpose.
For this you need to download SDWebImage for asynchronous downloading of image. You can download SDWebImage from link below.
You can use it in your Carousel.h class as
#import <SDWebImage/UIImageView+WebCache.h>
modify your setup method with below line.
[imageView sd_setImageWithURL:[NSURL URLWithString:self.images[i]]
placeholderImage:[UIImage imageNamed:#"placeholder.png"]];
For details refer github page of SDwebpage. DO let me know if you have any queries.
https://github.com/rs/SDWebImage#using-asynchronous-image-downloader-independently

How to use SDWebImage in my project

Iam using collectionview to load image.These images are loaded from url in background thread. Hence the scrolling is not smooth.The images in url get expired after seconds hence i want to update the image with new image.How can i use the SDWebImage to load image and make scrolling smooth? Can anyone please help me to solve this.
Use this code
[YOUR_CELL_NAME.YOUR_IMAGE_NAME setImageWithURL:[NSURL URLWithString:#"IMAGE URL"] placeholderImage:[UIImage imageNamed:#"PLACEHOLDER IMAGE NAME"]];
You need to integrate the sdwebimage classes in your code. After that make a import.
Download sdwebimage from here
#import "UIImageView+WebCache.h"
and in your collectionview method write following lines to download image in backend thread.
[YOUR_CELL_NAME.YOUR_IMAGE_NAME setImageWithURL:[NSURL URLWithString:#"IMAGE URL"] placeholderImage:[UIImage imageNamed:#"PLACEHOLDER IMAGE NAME"]];

iOS UITableViewCell Images from URL

I am loading images in my UITableViewCell from some web url and those images are in size around 80-100 kb per image. Everything works fine when i download images asynchronously but when i scroll the tableview, images start again downloading. Can i get rid of this as i have only limited no of rows.
I want if images from url download once should not be download again as it does makes view not comfortable for users when images starts downloading again.
I am using below code to load images in CellforRowAtIndexPath:
dispatch_async(dispatch_get_global_queue(0,0), ^{
NSData * data = [[NSData alloc] initWithContentsOfURL: [NSURL URLWithString:url];
if ( data == nil )
return;
dispatch_async(dispatch_get_main_queue(), ^{
cell.eventImage.image= [UIImage imageWithData:data];
});
});
You should use SDWebImage which will cache image on your device and if same image came from server then it load from your local device.
Add SDWebImage to your project.
import <SDWebImage/UIImageView+WebCache.h> header
then add below code at cellForItemAtIndexPath:
[cell.imageView sd_setImageWithURL:[NSURL URLWithString:#"your image URL"]
placeholderImage:[UIImage imageNamed:#"placeholder.png"]];
Better make use of SDWebImageCache for this because this a advantageous third party library to store the image in cache. After downloading once the images will be taken automatically from the cache.
SDWebImageCache
When you Download image put it to the document directory and before you download image check if document directory contains image then load it from there otherwise download from URL
If you want you can make it yourself. You can use NSCache in order to save your images. NSCache it is like NSMutableDictionary (save your image by key). And then you can check it. For key you can use path to your image.
But I also recommend you to use SDWebImage.

How to get the image from in memory cache using SDWebImage?

I have implemented SDWebImage in cellforrowatindexpath method. The problem here is when i scroll down the tableview the images are loading from web which is expected but when i scroll up the tableview the images are again downloading. What is the way to get rid of this problem. I don't want to load images from url overtime (since there is a usage limit with the web service call). I chose to use SDWebImage API for in memory cache so that once the images are loaded they are taken from cache to show it on the UI instead of making the web service call everytime. Here is my code:
[cell.placeImage sd_setImageWithURL:url placeholderImage:nil options:SDWebImageCacheMemoryOnly];
The above line is the only code in that method. Please help me.
Any kind of help is appreciated. I have seen other questions in this community but nobody said how to get an image from the cache memory.
For refreshing of the images you should use option : SDWebImageRefreshCached
[imageView sd_setImageWithURL:url placeholderImage:nil options:SDWebImageRefreshCached];

Use SDWebImage to download two images at once

I'm looking into using SDWebImage to download images into my app. I would like to show an image as quickly as possible, so I have two versions of each image on my server; one low quality and one high quality. Currently, I achieve this by using two NSURLRequest, one for each version of the image. This works perfectly as the app will download both versions simultaneously, show the low quality, then change the image to the high quality version when it's finished downloading.
I tried to replicate this by using:
[imageView setImageWithURL:lowURL];
[imageView setImageWithURL:highURL];
But when I run the app, the second call cancels the first one. Any help with this would be greatly appriciated.
Thanks
modify framework is not a good way to solve problem, unless there is no other better way.
in SDWebImage's UIImageView+WebCache.h category, there are methods for this situation.
eg:
__weak UIImageView *weakImageView = imageView;
[imageView setImageWithURL:thumbURL placeholderImage:nil completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType) {
[weakImageView setImageWithURL:bigURL placeholderImage:image];
}];
If you look into the - (void)setImageWithURL:(NSURL *)url in the UIImageView+WebCache.m file, you will find there is [self cancelCurrentImageLoad]; in the first line, which is cancel the current image loading operation. if you want to load both simultaneously, you can try to comment out this line to test whether it will work as you expected, if cannot then you'd better try other methods.
probably this issue is better being solved in a different way, try pre-fetching the image even before displaying it
this is the swift code to do so
let prefetcher = SDWebImagePrefetcher.shared()
let urls :[URL] = [URL(string: imageStringUrl)]
prefetcher.prefetchURLs(urls)

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