Importing Images through didReceivedData - iphone

Question

I am developing an application through which user can share images.Using php file I am uploading file on the server and downloading using php file.when i download file it is take bit long time.How do i make it little bit fast.
-(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
NSString *data1 = [[NSString alloc]initWithData:data encoding:NSUTF8StringEncoding];
NSArray *arrImg = [data1 componentsSeparatedByString:#"###"];
int i;
NSMutableArray *receivedUrlArr = [[NSMutableArray alloc]init];
NSString *str,*strNew,*path;
NSData *imageData;
ImagesClass *obj;
int count;
for ( i=0; i<[arrImg count]-1; i++) {
[receivedUrlArr addObject:[arrImg objectAtIndex:i]];
str = [NSString stringWithFormat:#"http:////receive_images/%#",[receivedUrlArr objectAtIndex:i]];
strNew = [str stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
UIImage *myImage = [[UIImage alloc] initWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:strNew]]];
obj = [[ImagesClass alloc]init];
obj.imageId = i+1;
obj.imageName = [[arrImg objectAtIndex:i] stringByReplacingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
obj.thumbImage = myImage;
[[DBModel database]inserttoReceivedList:obj receiverMobNo:mobileno];
path = [RECEIVEDIMAGE_DIR stringByAppendingPathComponent:[NSString stringWithFormat:#"%#",obj.imageName]];
imageData = UIImagePNGRepresentation(obj.thumbImage);
[imageData writeToFile:path atomically:YES];
}
}
Thanks in advance.

Answer 1

No matter how efficient your method for storing an image is, you will always be bottlenecked by the speed of the connection.
However, you seem to be going about this the wrong way. -connection:didReceiveData is for receiving data incrementally. It seems that you are assuming that once you receive the data, you have finished loading the image, then doing a complicated bit of processing to save the partially downloaded image. Instead, your delegate for NSURLConnection should implement -connectionDidFinishLoading. In this method, you will convert the concatenated data to an image and save it then.
Here is how I would set things up:
Let's assume you have a controller class that is displaying images/needs to download more images.
Now, create a class named something like "ImageDownloader" which implements NSURLConnection Delegate. When you initialize this class, you will provide it with an image name and a URL to the image that needs to be downloaded. Within ImageDownloader, you will need an NSMutableData property. Finally, you will need a method such as -startDownload to get things moving.
-startDownload should first make sure that your NSMutableData property is empty and initialized. Once that's done, you can start the NSURLConnection's download. Be sure to set the delegate to your instance of ImageDownloader. In -connection:didReceiveData, append the data that is received to your NSMutableData property. In -connectionDidFinishLoading, convert that NSMutableData property to an image and save it using the image's name that your controller provided. From there, let the controller instance know the image is saved through a delegate method call or a notification.
Hope this helps.
edit: IIRC, Apple provides some sample code called "ImageDownloader" which is pretty similar if this explanation is confusing.

Answer 2

I have developed a class called File Downloader which is depicted as below :
Step 1 : Create a "FileDownloader.h" and add this in it.
#import <Foundation/Foundation.h>
#protocol fileDownloaderDelegate <NSObject>
#optional
- (void)downloadProgres:(NSNumber*)percent forObject:(id)object;
#required
- (void)downloadingStarted;
- (void)downloadingFinishedFor:(NSURL *)url andData:(NSData *)data;
- (void)downloadingFailed:(NSURL *)url;
#end
#interface FileDownloader : NSObject
{
#private
NSMutableURLRequest *_request;
NSMutableData *downloadedData;
NSURL *fileUrl;
id <fileDownloaderDelegate> delegate;
double totalFileSize;
}
#property (nonatomic, strong) NSMutableURLRequest *_request;
#property (nonatomic, strong) NSMutableData *downloadedData;
#property (nonatomic, strong) NSURL *fileUrl;
#property (nonatomic, strong) id <fileDownloaderDelegate> delegate;
- (void)downloadFromURL:(NSString *)urlString;
#end
Step 2 : Create a "FileDownloader.m" and write following
#import "FileDownloader.h"
#implementation FileDownloader
#synthesize _request, downloadedData, fileUrl;
#synthesize delegate;
- (void)downloadFromURL:(NSString *)urlString
{
[self setFileUrl:[NSURL URLWithString:[urlString stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]]];
self._request = [NSMutableURLRequest requestWithURL:self.fileUrl cachePolicy:NSURLRequestReloadIgnoringCacheData timeoutInterval:60.0f];
NSURLConnection *cn = [NSURLConnection connectionWithRequest:self._request delegate:self];
[cn start];
}
#pragma mark - NSURLConnection Delegate
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
if([delegate respondsToSelector:#selector(downloadingStarted)])
{
[delegate performSelector:#selector(downloadingStarted)];
}
totalFileSize = [response expectedContentLength];
downloadedData = [NSMutableData dataWithCapacity:0];
}
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
[downloadedData appendData:data];
if([delegate respondsToSelector:#selector(downloadProgres:forObject:)])
{
[delegate performSelector:#selector(downloadProgres:forObject:) withObject:[NSNumber numberWithFloat:([downloadedData length]/totalFileSize)] withObject:self];
}
}
- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
if([delegate respondsToSelector:#selector(downloadingFailed:)])
{
[delegate performSelector:#selector(downloadingFailed:) withObject:self.fileUrl];
}
}
- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
if([delegate respondsToSelector:#selector(downloadingFinishedFor:andData:)])
{
[delegate performSelector:#selector(downloadingFinishedFor:andData:) withObject:self.fileUrl withObject:self.downloadedData];
}
}
#end
Step 3 : Now Import "#import "FileDownloader.h"" in your viewcontroller and "fileDownloaderDelegate" Delegate in .h file
Step 4 : Create Object , Set Delegate and URL to Download file.
FileDownloader *objDownloader = [[FileDownloader alloc] init];
[objDownloader setDelegate:self];
[objDownloader downloadFromURL:#"yourURL"];
Step 5 : Dont forget to implement Delegate methods in your view controller to get notify about download progress. enjoy..