In my iOS App,I have hundreds of image download.
I use AFNetworking to get those images.I want to manage the request number of AFWorking.
This is my code:
The problem is:It will block my UI.
THX for help me!
dispatch_group_t group = dispatch_group_create();
dispatch_queue_t queue = dispatch_queue_create(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
dispatch_semaphore_t semaphore = dispatch_semaphore_create(5);
for (NSString *urlString in self.downloadImageList) {
dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER);
dispatch_group_async(group, queue, ^{
NSURL *url = [NSURL URLWithString:urlString];
NSURLRequest *request = [NSURLRequest requestWithURL:url];
NSString *filename = url.lastPathComponent;
NSURL *outputFileURL = APPLICATION_DOCUMENTS_DIRECTORY;
outputFileURL = [outputFileURL URLByAppendingPathComponent:[NSString stringWithFormat:#"%#/images/%#",self.boardId,filename]];
dispatch_group_async(group, dispatch_get_main_queue(), ^{
AFHTTPRequestOperation *operation = [[AFHTTPRequestOperation alloc] initWithRequest:request];
operation.outputStream = [NSOutputStream outputStreamWithURL:outputFileURL append:YES];
[operation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject) {
[self.downloadImageList removeObject:urlString];
NIDINFO(#"download success %#",filename);
dispatch_semaphore_signal(semaphore);
} failure:^(AFHTTPRequestOperation *operation, NSError *error) {
NIDERROR(#"download image error:%#\n%#",error,urlString);
dispatch_semaphore_signal(semaphore);
}];
[operation start];
});
});
}
dispatch_group_wait(group, DISPATCH_TIME_FOREVER);
dispatch_release(semaphore);
dispatch_release(group);
The problem is: It will block my UI.
Well yeah, that's sort of the point of dispatch_semaphore_t. If you remove those calls, your AFNetworking calls will execute asynchronously in the background without affecting your main / UI thread.
I don't know the full context of where this code is being used, but it looks like you may want to consider having the method that calls this take a block parameter, that can be called once all of the requests have finished. You may also want to take a look at AFHTTPClient's batch operations features, which allows you to track the progress of a group of operations, getting callbacks for each individually, and when all of then finish.
Related
I'm using AFNetworking to download more or less 200 images. The problem is that the main thread is blocked during the download, not during the success/failure block.
Here is my code:
imageDownloads=[[NSMutableArray alloc]init];
for(NSString *url in liens){
NSString *totalURL = [NSString stringWithFormat:#"http://%#", url];
[imageDownloads addObject:[[ImageDownload alloc] initWithURL:[NSURL URLWithString:totalURL] filename:nil]];
}
for (int i=0; i < imageDownloads.count; i++)
{
ImageDownload *imageDownload = imageDownloads[i];
[self downloadImageFromURL:imageDownload];
}
- (void)downloadImageFromURL:(ImageDownload *)imageDownload
{
NSURLRequest *request = [NSURLRequest requestWithURL:imageDownload.url];
AFHTTPRequestOperation *operation = [[AFHTTPRequestOperation alloc] initWithRequest:request];
[operation setDownloadProgressBlock:^(NSUInteger bytesRead, long long totalBytesRead, long long totalBytesExpectedToRead) {
imageDownload.totalBytesRead = totalBytesRead;
imageDownload.totalBytesExpected = totalBytesExpectedToRead;
[self updateProgressView];
}];
[operation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject) {
NSAssert([responseObject isKindOfClass:[NSData class]], #"expected NSData");
imageDownload.totalBytesExpected = imageDownload.totalBytesRead;
[self updateProgressView];
//all kind of basic stuff here I left out: I get store the data inside CoreData
NSLog(#"finished %#", imageDownload);
} failure:^(AFHTTPRequestOperation *operation, NSError *error) {
NSLog(#"error %#", error);
}];
[operation start];
}
Basically, when I launch the code, the thread is blocked for like 30-40 seconds (the pictures are about 100MB in total), and then suddenly I can see all the NSLog logs appear with the "Finished"... text. So that part if really quick. But I thought AFNetworking wasn't supposed to block the main thread while I was downloading? This also doesn't allow me to track the progress of the download...Am I doing something wrong or misinterpreting something?
You're updating the progress view in the progress block. Because AFNetworking is inherently async anyway, each of these requests will stack and run at the same time. If you're running 200 of them, that's going to freeze up the app. Try using NSOperationQueue's maxConcurrentOperationCount to limit the number of concurrent threads.
Alternatively, you could save all the trouble and just use sdwebimage.
I tried to use afnetworking for a simple testing, but it seemed that the success/failure blcok was not triggered at all, is there anything I forgot to set up?
My code is below:
int main(int argc, const char * argv[]) {
#autoreleasepool {
NSString *string = [NSString stringWithFormat:#"%#weather.php?format=json", BaseURLString];
NSURL *url = [NSURL URLWithString:string];
NSURLRequest *request = [NSURLRequest requestWithURL:url];
AFHTTPRequestOperation *operation = [[AFHTTPRequestOperation alloc] initWithRequest:request];
operation.responseSerializer = [AFJSONResponseSerializer serializer];
[operation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject) {
NSLog(#"Succeed!");
} failure:^(AFHTTPRequestOperation *operation, NSError *error) {
NSLog(#"Fail");
}];
[operation start];
}
return 0;
}
Updated: I tried use a loop a to wait the operation to execute and print out, but nothing was printed out. Here is my updated version
int main(int argc, const char * argv[]) {
#autoreleasepool {
__block bool result = false;
NSString *string = [NSString stringWithFormat:#"%#weather.php?format=json", BaseURLString];
NSURL *url = [NSURL URLWithString:string];
NSURLRequest *request = [NSURLRequest requestWithURL:url];
AFHTTPRequestOperation *operation = [[AFHTTPRequestOperation alloc] initWithRequest:request];
operation.responseSerializer = [AFJSONResponseSerializer serializer];
[operation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject) {
NSLog(#"Succeed!");
result = true;
} failure:^(AFHTTPRequestOperation *operation, NSError *error) {
NSLog(#"Fail");
result = true;
}];
[operation start];
while (1) {
if (result) {
break;
}
}
}
return 0;
}
Yes they will not be called because the program exits out before the operation even starts.
The main function returns 0 and the program ends and the operation have still not started.
You need to read more on asynchronous blocks.
A common and simple approach to solve this problem (having an async function and a continuation) in a console test app would leveraging a semaphore which you wait on in the main function before you exit and release it in the continuation, which runs on some other thread. Now, the main thread will be blocked when waiting on the semaphore up until the semaphore gets released when the continuation has been run. Quite simple.
If you want to try out AFN in an console application, however, this does not work. You need to use a run loop which adds some undesired complexity in order to get this simple test app to run. This is unfortunate, and stems from the simple fact that AFN executes its continuations on the main thread. IMHO, this is is a very bad design decision, which can lead to dead locks (as it would happen in your case) and is also less efficient.
So, your approach would use a RunLoop where you basically loop and check a flag for the condition "done" which is set by the continuation (the completion blocks). Since you are reading an writing the flag on the main thread only, you don't get a data race - that is, it should be thread safe.
I'm trying to figure out a way to download multiple images with AFNewtorking 2.0. I've read a lot of posts here in SO, but can't find the answer I'm looking for, hope you guys can help me.
The problem is that I want to know when all of the downloads finished and if all images where downloaded.
So I have an array with image URL's ant trying to do something like this.
for(NSString *photoUrlString in self.photos){
NSURL *url = [NSURL URLWithString:photoUrlString];
AFHTTPRequestOperation *requestOperation = [[AFHTTPRequestOperation alloc] initWithRequest:[NSURLRequest requestWithURL:url]];
requestOperation.responseSerializer = [AFImageResponseSerializer serializer];
[requestOperation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject) {
} failure:^(AFHTTPRequestOperation *operation, NSError *error) {
NSLog(#"Image error: %#", error);
}];
[requestOperation start];
}
I've found some answers with putting these requests into a queue and setting max concurrent operations to 1. But don't know how that works really.
Any help is appreciated, thanks in advance!
for(Photo *photo in array){
//form the path where you want to save your downloaded image to
NSString *constPath = [photo imageFullPath];
//url of your photo
NSURL *url = [NSURL URLWithString:photo.serverPath];
AFHTTPRequestOperation *op = [[AFHTTPRequestOperation alloc] initWithRequest:[NSURLRequest requestWithURL:url]];
op.responseSerializer = [AFImageResponseSerializer serializer];
op.outputStream = [NSOutputStream outputStreamToFileAtPath:constPath append:NO];
op.queuePriority = NSOperationQueuePriorityLow;
[op setDownloadProgressBlock:^(NSUInteger bytesRead, long long totalBytesRead, long long totalBytesExpectedToRead){
}];
op.completionBlock = ^{
//do whatever you want with the downloaded photo, it is stored in the path you create in constPath
};
[requestArray addObject:op];
}
NSArray *batches = [AFURLConnectionOperation batchOfRequestOperations:requestArray progressBlock:^(NSUInteger numberOfFinishedOperations, NSUInteger totalNumberOfOperations) {
} completionBlock:^(NSArray *operations) {
//after all operations are completed this block is called
if (successBlock)
successBlock();
}];
[[NSOperationQueue mainQueue] addOperations:batches waitUntilFinished:NO];
Try this:
// _group, _queue are iVar variable
dispatch_group_t *_group = dispatch_group_create();
dispatch_queue_t *_queue = dispatch_queue_create("com.company.myqueue2", NULL);
// all files download
for(int i = 0 ; i < numberOfFileDownloads; i++){
dispatch_group_async(_group, _queue, ^{
// here is background thread;
// download file
});
}
// all files are download successfully, this method is called
dispatch_group_notify(_group, _queue, ^{
}
Check out +[AFURLConnectionOperation batchOfRequestOperations:progressBlock:completionBlock:]
Although it's not documented, implementation is self-explanatory. Also it allows you to monitor the progress.
You will need to have an array of HTTP operations prior to using this method (this is if you decided to stick to NSURLConnection-based implementation of AFNetworking).
I download asynchronously some object, I store it in array. Next for each object I download some coordinates with geocoding (it is also asynchronously), and update my database for each object with new parameters which is coordinate. My method looks like this:
- (void)downloadObjectsWithTitle:(NSString *)title andHandler:(void(^)(NSMutableDictionary *result))handler {
AFHTTPClient *httpClient = [[AFHTTPClient alloc] initWithBaseURL:url];
NSMutableURLRequest *request = [httpClient requestWithMethod:#"GET"
path:nil
parameters:nil];
AFHTTPRequestOperation *operation = [[AFHTTPRequestOperation alloc] initWithRequest:request];
[httpClient registerHTTPOperationClass:[AFHTTPRequestOperation class]];
[operation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject) {
//I get here array of objects
//now for each object I want to download geocoding localization so i called another asynchronyous method getLocationWithTitle:andHandler;
for(int i = 0; i < resutArray.count; i++) {
[self downloadLocationWithString:[dictionary objectForKey:#"string"] andHandler:^(NSMutableDictionary *result) {
//update database;
}];
}
handler(dictionary);
} failure:^(AFHTTPRequestOperation *operation, NSError *error) {
NSLog(#"Error: %#", error);
}];
[operation start];
}
My question is how to downalod coordinates for each object and that fire:
handler(dictionary);
so wait for each coordinates download (for each object) before quit method (fire handler).
Thnaks for all sugestions.
Maintain a count of all the tasks. When it's zero you're done.
Assuming you're using dispatch_async in downloadLocationWithString: on a concurrent queue:
dispatch_barrier_async(queue, ^{
// will only be called after all the blocks submitted to queue have finished.
}];
(If you're using serial queue, simply call handler at the last line of the last block)
Try a global flag. set NO first. In download block, after download complete set flag to yes. You can check that flag.
EDIT: The highlighted row in the screenshot is what I have a problem with, why is NSURLConnection running on [NSThread main] when I'm not calling it, AFNetworking is.
I'm using AFNetworking for my project, but when running Time Profiler in Instruments I'm seeing a lot of activity on the main thread for NSURLConnection, I have a feeling this is not what I want.
My method is
- (void)parseArticles {
NSMutableArray *itemsToParse = [[FMDBDataAccess sharedDatabase] getItemsToParse];
NSMutableArray *operations = [[NSMutableArray alloc] init];
for (Post *p in itemsToParse) {
NSMutableString *strURL = [NSMutableString new];
[strURL appendString:#"http://xxxxxxxxxxxxxxxxxxxxxx.php?url="];
[strURL appendString:[p href]];
NSURL *url = [NSURL URLWithString:strURL];
NSURLRequest *request = [NSURLRequest requestWithURL:url];
AFHTTPRequestOperation *operation = [[AFHTTPRequestOperation alloc] initWithRequest:request];
[[ParserClient sharedInstance] registerHTTPOperationClass:[AFHTTPRequestOperation class]];
[operation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject) {
dispatch_async(loginParseQueue, ^{
Parser *parse = [[Parser alloc] init];
[parse parseLink:responseObject rowID:[p rowID]];
});
} failure:^(AFHTTPRequestOperation *operation, NSError *error) {
NSLog(#"%#",error);
}];
[operations addObject:operation];
}
NSOperationQueue *operationQueue = [[NSOperationQueue alloc] init];
[operationQueue setMaxConcurrentOperationCount:3];
[operationQueue addOperations:operations waitUntilFinished:NO];
}
Why would AFNetworking be using the main thread? and how do I fix it.
AFNetworking is running on a child thread not in main thread, but every thread has a main method, which is on the image you post. This is not the main thread.Now tell me What do you want to fix?
It's because AFNetworking uses "successCallbackQueue" to route the completion block :
AFHTTPRequestOperation.m :
self.completionBlock = ^{
if (self.error) {
if (failure) {
dispatch_async(self.failureCallbackQueue ?: dispatch_get_main_queue(), ^{
failure(self, self.error);
});
}
} else {
if (success) {
dispatch_async(self.successCallbackQueue ?: dispatch_get_main_queue(), ^{
success(self, self.responseData);
});
}
}
};
You can simply assign a different thread to success and failure completion blocks :
dispatch_queue_t backgroundQueue = dispatch_queue_create("com.name.bgqueue", NULL);
AFHTTPRequestOperation *operation = [[AFHTTPRequestOperation alloc] initWithRequest:request];
operation.successCallbackQueue = backgroundQueue;
operation.failureCallbackQueue = backgroundQueue;
EDIT:
Here is some code to run operations in a background thread. Use of any function called from the UI thread will run on on the UI thread. You can use a technique similar to the one specified below to run your operation on a background thread, and then dispatch the result back to the UI thread for later use.
Here is the technique I used, you may replace my sendSynchronousRequest call with your AFHTTPRequestOperation :
Specify a special type (a block) so you can pass blocks of code around.
typedef void (^NetworkingBlock)(NSString* stringOut);
Then, you need to dispatch to a background thread, so as not to freeze your UI thread.
Here's a function to call stuff in a background thread, and then wait for a response, and then call a block when done without using the UI thread to do it:
- (void) sendString:(NSString*)stringIn url:(NSString*)url method:(NSString*)method completion:(NetworkingBlock)completion {
//build up a request.
NSMutableURLRequest* request = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:url]];
NSData *postData = [stringIn dataUsingEncoding:NSUTF8StringEncoding];
[request setHTTPMethod:method];
[request setValue:[NSString stringWithFormat:#"%d", postData.length] forHTTPHeaderField:#"Content-Length"];
[request setValue:#"application/json" forHTTPHeaderField:#"Content-Type"]; //or whatever
[request setHTTPBody:postData];
//dispatch a block to a background thread using GCD (grand central dispatch)
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
NSURLResponse *response;
NSError* error;
//request is sent synchronously here, but doesn't block UI thread because it is dispatched to another thread.
NSData* responseData = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&error];
//call complete, so now handle the completion block.
if (completion) {
//dispatch back to the UI thread again
dispatch_async(dispatch_get_main_queue(), ^{
if (responseData == nil) {
//no response data, so pass nil to the stringOut so you know there was an error.
completion(nil);
} else {
//response received, get the content.
NSString *content = [[NSString alloc] initWithBytes:[responseData bytes] length:responseData.length encoding:NSUTF8StringEncoding];
NSLog(#"String received: %#", content);
//call your completion handler with the result of your call.
completion(content);
}
});
}
});
}
Use it like this:
- (void) myFunction {
[self sendString:#"some text in the body" url:#"http://website.com" method:#"POST" completion:^(NSString *stringOut) {
//stringOut is the text i got back
}];
}