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];
Related
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 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.
I am using SDWebImage library for handling image cache. I implemented one of its method to download image from server and populating data in tableView. Here is my code for downloading image and showing in tableViewCell
In cellForRowAtIndexPath, I did the following code
[cell.profileImageView sd_setImageWithURL:[NSURL URLWithString:url] placeholderImage:nil options:SDWebImageRefreshCached];
It works perfectly here. But when I updated image on server, the tableViewCell still shows the same image. The problem is ,its cache is not updating image. I searched with the same keywords and came across this question on StackOverflow. But couldn't resolve the issue. I also tried to clear memory and cache on viewDidDisappear
-(void)viewDidDisappear:(BOOL)animated
{
[super viewDidDisappear:YES];
[[SDImageCache sharedImageCache]clearMemory];
[[SDImageCache sharedImageCache]clearDisk];
}
But its not efficient way. Is there any other way to update the cache when image on server is updated ?
You can use SDWebImageRefreshCached option to refresh concrete image, however you never know if the image was changed on the server side. So it's only your decision should you use image cache or not and when your cache should be updated.
From SDWebImage docs :
If you don't control the image server you're using, you may not be able to change the URL when its content is updated. In such case, you may use the SDWebImageRefreshCached flag. This will slightly degrade the performance but will respect the HTTP caching control headers
[imageView sd_setImageWithURL:url
placeholderImage:[UIImage imageNamed:#"placeholder.png"]
options:SDWebImageRefreshCached];
It would defeat the purpose of Image Caching if you use this in all your code. Coz the image will be downloaded everytime. Instead you could :
If you manage the server, you could setup some flags in the DB to indicate the image has changed on the server.
Implement some logic to only use SDWebImageRefreshCached once in 2 days or something like that, and use the normal code all other times.
You could also clear the entire cache once in a while to force a refresh, if that's feasible.
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];
I am encountering a very strange issue in my application.
I have used SDWebImage in the application, to download the images to cache, when network present and then retrieve the images from the cache, when absent.
The SDWebImage works perfectly in case of UITableViews. One can even see the stored/cached image files in the iPhone Simulator folder.
And then theres this one piece of code, that is troubling me.
I am displaying a simple imageview, and caching the image from the network.
The image is displayed properly, when network is present.
But in case of no connectivity, nothing is displayed.
Am assuming, that the caching is not taking place.
Lines of code
dispatch_async(dispatch_get_main_queue(), ^{
[im setImageWithURL:[NSURL URLWithString:[[NSString stringWithFormat:#"%#%#",kImgaePath,[[marrresultingArraySet objectAtIndex:0] objectAtIndex:kIndex_RecipeImage_Local]] stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]] placeholderImage:[UIImage imageNamed:#"no_imagepng.jpg"]];});