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.
Related
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
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"]];
I am using SDWebImage framework to cache the images in my application.
I have stored all urls in Database. The url is coming correctly, but only the placeholder image is displaying.
[cell.productCategoryImg sd_setImageWithURL:[NSURL URLWithString:imgStr]
placeholderImage:[UIImage imageNamed:#"zamor.png"]
options:SDWebImageRefreshCached];
I have an app where it pulls urls of images from a database and stores it in coredata. Then in my app view, there's a scrollview of imageviews, basically I'm trying to do an image slider. These images tend to get updated so it needs to load from the server. I load the image urls from the coredata, download them to uiimages and load them in my view. Problem is, it's really slow as I'm doing it at runtime.
I was wondering what's the best way to go about this. I was thinking of loading all the images to the phone first when the app launches? I tried looking for some sample code to point me to the right direction but I can only find code that saves images to the phone's camera roll and not to the app itself. Anyone could help pls? Thanks!
Here's a method that takes a UIImage, a target path (the directory you want to save the image to) and the filename for the image, and saves the image as a PNG file:
-(BOOL) saveImage:(UIImage *)image savePath:(NSString *)savePath filename:(NSString *)filename{
savePath = [savePath stringByAppendingPathComponent:filename];
NSData *sourceData = UIImagePNGRepresentation(image);
return [sourceData writeToFile:savePath atomically:YES];
}
You will need to store the image in the right location within the app's sandbox. For example, don't put them in the Documents folder as it may be rejected by Apple since you can recreate (or re-download) the images. You likely want to put them in the Library/Caches folder, and be prepared to re-download them if they are removed. See the iOS File System Programming Guide for details on this.
I would be concerned about downloading all the files at app start, since it will look like the app has frozen if it non-responsive while download a number of image files. You can download the images in the background and update the UI as the images finish downloading.
One method to do this would be to check if the image has already been downloaded (e.g., is it in the Library/Caches folder). If it is, then use it, otherwise use a placeholder image until the image is downloaded. For example:
if (isImageAvailable) {
displayedImageView.image = cachedImage;
} else {
displayedImageView.image = placeholderImage;
[self getImageAtURL:imageURL andThenDo:^(UIImage *image) {
// Replace placeholder image with downloaded image
displayedImageView.image = image;
}];
}
Replace isImageAvailable with a method that checks for the existence of the image file in the Library/Caches folder. displayedImageView is the UIImageView you are displaying the image with.
The getImageAtURL method would look something like:
-(void)getImageAtURL:(NSURL *)url andThenDo:(void(^)(UIImage *image))completionBlock{
// Run on background thread
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
UIImage *image;
// Insert code to download image...
// Switch to main (UI) thread to allow updating the UI
dispatch_sync(dispatch_get_main_queue(), ^{
completionBlock(image);
});
});
}
You might not need to download images to your application, I can suggest better you use image url it self to load images from server it self.
To load images from server u may use following:
UIImage* yourImageview = [UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:your.image_url]]];
Downloading all images will also slow down your app.
I use SDWebImage in my app. I have several UIImageView in my viewcontroller, and
all of them use setImageWithURL: method(in UIImageView+WebCache.m)
load image by URL. There are three images should be load, two images
about 520kb, and the little one is 180kb. While I do run it , it will
receive memory warning and crash, I have no idea about it. Can anyone
help me, thanks!
Here is my code:
NSDictionary *data = [respDic objectForKey:#"data"];
[self.topLeft setImageWithURL:[NSURL URLWithString:[data valueForKey:#"tr_cu_1"]]];
[self.bottomLeft setImageWithURL:[NSURL URLWithString:[data valueForKey:#"tr_cu_2"]]];
[self.bottomRight setImageWithURL:[NSURL URLWithString:[data valueForKey:#"tr_cu_3"]]];