I have tried some ways to perform NSURLConnection when lock the screen but none of it works.
I have tried as following:
[self performSelectorInBackground:#selector(startConnection) withObject:nil];
I also tried:
dispatch_queue_t request_queue = dispatch_queue_create("com.app.download", NULL);
dispatch_async(request_queue, ^{
[self startConnection];
});
in startConnection:
- (void)startConnection{
... some URL processing
responseData_ = [[NSMutableData alloc] init];
connection_ =
[[NSURLConnection alloc] initWithRequest:urlRequest delegate:self];
}
The NSURLConnection delegate methods aren't called by this way.
What is the real code to make it works? Thanks!
A small update that may help:
It only calls this delegate method:
- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
with message:
A server with the specified hostname could not be found.
I am very sure my wi-fi is connected, still not sure why it is called :(
If you lock your screen, your app will be turn into background mode, not background running mode.
If you want to download while user locks the screen, you should check this method [UIApplication -beginBackgroundTaskWithExpirationHandler:]
Related
I have a problem loading a large web page in a UIWebView where the connection drops for some reason trying to load a java script file. The load stalls at the point with neither didFailLoadWithError or webViewDidFinishLoad ever being invoked. The delegate is setup correct as when there is no networking error the page loads fine and the webViewDidFinishLoad method is invoked.
While trying to figure out why the page load stalls I implemented and registered a custom NSURLProtocol where I found out that connection delegate didFailWithError would be invoked most of the time, but the web view delegate would never be invoked after that.
I changed the custom protocol to run the connection in the main thread, which caused the didFailWithError method to be invoked every time the network connection dropped
- (void)startLoading {
NSMutableURLRequest *newRequest = [self.request mutableCopy];
[NSURLProtocol setProperty:#YES forKey:ProtocolKey inRequest:newRequest];
self.connection = [[NSURLConnection alloc]
initWithRequest:newRequest
delegate:self startImmediately:NO];
[self.connection scheduleInRunLoop:[NSRunLoop mainRunLoop]
forMode:NSDefaultRunLoopMode];
[self.connection start];
}
The web view delegate webViewDidFinishLoad method was still not being called so I added a notification to the didFailWithError method, which allows me to handle the error in my web view controller
- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error {
NSDictionary *dict = #{ #"errorDescription":error.localizedDescription };
[[NSNotificationCenter defaultCenter] postNotificationName:ErrorKey object:nil ];
[self.client URLProtocol:self didFailWithError:error];
}
I can't figure out why it seems that the request being run by the web view on the background thread seem to get destroyed before the delegate methods can be invoked and the errors handled?
I was having similar issues with WKWebView, I assume with the same resource javascript, but I can not trap the errors in the custom protocol handler so I don't know what is going on there.
Has any one run into this before? Or have a better way of resolving this problem?
I start a NSURLConnection in another thread:
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0),
^{
NSURLConnection *connection = [NSURLConnection connectionWithRequest:[request preparedURLRequest] delegate:self];
[connection start];
});
But my delegate method is not called:
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData*)data;
When run on the main thread everything is fine. How can I run connection on another thread and get the delegate methods called at the same thread too?
GCD creates, destroys, reuses threads implicitly and there is a chance that the thread you call start from will stop existing immediately afterwards. This may result in the delegate not receiving any callbacks.
If you would like to receive callback in background thread, you can use setDelegateQueue or sendAsynchronousRequest:queue:completionHandler: method:
NSURLConnection* connection = [[NSURLConnection alloc] initWithRequest:request
delegate:self
startImmediately:NO];
[connection setDelegateQueue:[[NSOperationQueue alloc] init]];
[connection start];
The easiest way to start NSURLConnection in the background thread via GCD is:
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0),
^{
NSURLResponse* response = nil;
NSError* error = nil;
[NSURLConnection sendSynchronousRequest:request] returningResponse:&response error:&error];
NSLog(#"%#", response);
});
Yes, this is well known behavior of NSURLConnection because it needs a run loop to process the delegate events. The most common solution is (a) instantiate it with initWithRequest:delegate:startImmediately: where startImmediately is FALSE; (b) manually scheduleInRunLoop:forMode: to schedule it in the main run loop; and then (c) start the connection.
But, as you have it here, there's no point in dispatching this to a background queue, as it's already asynchronous so you should just initiate this from the main queue and none of the above is necessary. You use the above pattern in special cases (e.g. you were using NSOperation subclass to manage your requests), but generally it's not needed.
Also, FYI, effective iOS9, NSURLConnection is deprecated, so you should be using NSURLSession, anyway. And NSURLSession doesn’t suffer this limitation.
I had a similar issue. What I'm doing now is running NSURLConnection request in the main thread - it is running asynchronously so it won't slow down your application. In connectionDidFinishLoading, I run the following code to process the results of my calls. I perform the check because I have NSURLConnection call which may trigger other network calls. Since they are already running on a background thread I don't want to start a new one.
- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
if ([NSThread isMainThread]) {
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^(void){
//Background Thread
[self processFinishLoading:connection];
});
}
else {
[self processFinishLoading:connection];
}
}
I've read through tons of messages saying the same thing all over again : when you use a NSURLConnection, delegate methods are not called. I understand that Apple's doc are incomplete and reference deprecated methods, which is a shame, but I can't seem to find a solution.
Code for the request is there :
// Create request
NSURL *urlObj = [NSURL URLWithString:url];
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:urlObj cachePolicy:NSURLRequestReloadIgnoringCacheData timeoutInterval:30];
[request setValue:#"gzip" forHTTPHeaderField:#"Accept-Encoding"];
if (![NSURLConnection canHandleRequest:request]) {
NSLog(#"Can't handle request...");
return;
}
// Start connection
dispatch_async(dispatch_get_main_queue(), ^{
self.connection = [[NSURLConnection alloc] initWithRequest:request delegate:self startImmediately:YES]; // Edited
});
...and code for the delegate methods is here :
- (void) connection:(NSURLConnection *)_connection didReceiveResponse:(NSURLResponse *)response {
NSLog(#"Receiving response: %#, status %d", [(NSHTTPURLResponse*)response allHeaderFields], [(NSHTTPURLResponse*) response statusCode]);
self.data = [NSMutableData data];
}
- (void) connection:(NSURLConnection *)_connection didFailWithError:(NSError *)error {
NSLog(#"Connection failed: %#", error);
[self _finish];
}
- (void) connection:(NSURLConnection *)_connection didReceiveData:(NSData *)_data {
[data appendData:_data];
}
- (void)connectionDidFinishDownloading:(NSURLConnection *)_connection destinationURL:(NSURL *) destinationURL {
NSLog(#"Connection done!");
[self _finish];
}
There's not a lot of error checking here, but I've made sure of a few things :
Whatever happens, didReceiveData is never called, so I don't get any data
...but the data is transfered (I checked using tcpdump)
...and the other methods are called successfully.
If I use the NSURLConnectionDownloadDelegate instead of NSURLConnectionDataDelegate, everything works but I can't get a hold on the downloaded file (this is a known bug)
The request is not deallocated before completion by bad memory management
Nothing changes if I use a standard HTML page somewhere on the internet as my URL
The request is kicked off from the main queue
I don't want to use a third-party library, as, ultimately, these requests are to be included in a library of my own, and I'd like to minimize the dependencies. If I have to, I'll use CFNetwork directly, but it will be a huge pain in the you-know-what.
If you have any idea, it would help greatly. Thanks!
I ran into the same problem. Very annoying, but it seems that if you implement this method:
- (void)connectionDidFinishDownloading:(NSURLConnection *)connection destinationURL:(NSURL *)destinationURL
Then connection:didReceiveData: will never be called. You have to use connectionDidFinishLoading: instead... Yes, the docs say it is deprecated, but I think thats only because this method moved from NSURLConnectionDelegate into NSURLConnectionDataDelegate.
I like to use the sendAsynchronousRequest method.. there's less information during the connection, but the code is a lot cleaner.
[NSURLConnection sendAsynchronousRequest:request queue:[[NSOperationQueue alloc] init] completionHandler:^(NSURLResponse *response, NSData *data, NSError *error){
if (data){
//do something with data
}
else if (error)
NSLog(#"%#",error);
}];
From Apple:
By default, a connection is scheduled on the current thread in the
default mode when it is created. If you create a connection with the
initWithRequest:delegate:startImmediately: method and provide NO for
the startImmediately parameter, you can schedule the connection on a
different run loop or mode before starting it with the start method.
You can schedule a connection on multiple run loops and modes, or on
the same run loop in multiple modes.
Unless there is a reason to explicitly run it in [NSRunLoop currentRunLoop],
you can remove these two lines:
[connection scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSRunLoopCommonModes];
[connection start];
or change the mode to NSDefaultRunLoopMode
NSURLConnection API says " ..delegate methods are called on the thread that started the asynchronous load operation for the associated NSURLConnection object."
Because dispatch_async will start new thread, and NSURLConnection will not pass to that other threat the call backs, so do not use dispatch_async with NSURLConnection.
You do not have to afraid about frozen user interface, NSURLConnection providing only the controls of asynchronous loads.
If you have more files to download, you can start some of connection in first turn, and later they finished, in the connectionDidFinishLoading: method you can start new connections.
int i=0;
for (RetrieveOneDocument *doc in self.documents) {
if (i<5) {
[[NSURLConnection alloc] initWithRequest:request delegate:self];
i++;
}
}
..
-(void)connectionDidFinishLoading:(NSURLConnection *)connection
{
ii++;
if(ii == 5) {
[[NSURLConnection alloc] initWithRequest:request delegate:self];
ii=0;
}
}
One possible reason is that the outgoing NSURLRequest has been setup to have a -HTTPMethod of HEAD. Quite hard to do that by accident though!
I'm trying to pull images from the server for the scrollview. After the user zooms the view in or out, the image should be downloaded:
- (void)scrollViewDidEndZooming:(UIScrollView *)scrollView withView:(UIView *)view atScale:(float)scale {
Ymin=365000+375000*_scrollView.contentOffset.x/(scale*1024);
Ymax=365000+375000*(_scrollView.contentOffset.x/scale+1024/scale)/1024;
Xmin=6635000-260000*(_scrollView.contentOffset.y/scale+748/scale)/748;
Xmax=6635000-260000*_scrollView.contentOffset.y/(scale*748);
[self looYhendus]; //Creates NSURLConnection and downloads the image according to scale, Ymin, Ymax, Xmin and Xmax values
UIImage *saadudPilt=_kaardiPilt;
imageView=[[UIImageView alloc] initWithImage:saadudPilt];
imageView.frame=CGRectMake(_scrollView.contentOffset.x,_scrollView.contentOffset.y,1024,748);
[_scrollView addSubview:imageView];
}
On some occasions (I can't figure out, on what conditions), it works, but on some occasions NSURLConnection delegate methods won't get fired and the image set as the subview is still the image that is initially downloaded (when the application launches). Then, only after I touch the screen again (the scrollview scrolls), the NSLog message shows that the image is downloaded. What could be the reason of this kind of a behaviour?
EDIT: Added the NSURLConnection delegate methods. I've tried a few other ways but they all end up not executing the delegate methods. Which made me think that it's not about NSURConnection but rather UIScrollView (obviously, I can be wrong about this).
- (void)looYhendus
{
yhendused=CFDictionaryCreateMutable(
kCFAllocatorDefault,
0,
&kCFTypeDictionaryKeyCallBacks,
&kCFTypeDictionaryValueCallBacks);
NSString *aadress = [NSString stringWithFormat:#"http://xgis.maaamet.ee/wms-pub/alus?version=1.1.1&service=WMS&request=GetMap&layers=MA-ALUSKAART&styles=default&srs=EPSG:3301&BBOX=%d,%d,%d,%d&width=%d&height=%d&format=image/png",Ymin,Xmin,Ymax,Xmax,512,374];
NSURL *url = [[NSURL alloc] initWithString:aadress];
NSMutableURLRequest *theRequest = [NSMutableURLRequest requestWithURL:url];
NSURLConnection *theConnection = [[NSURLConnection alloc] initWithRequest:theRequest delegate:self];
if( theConnection )
{
andmedServerist = [NSMutableData data];
CFDictionaryAddValue(
yhendused,
(__bridge void *)theConnection,
(__bridge_retained CFMutableDictionaryRef)[NSMutableDictionary
dictionaryWithObject:[NSMutableData data]
forKey:#"receivedData"]);
}
CFRunLoopRun();
}
-(void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
[andmedServerist setLength: 0];
}
-(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
NSMutableDictionary *connectionInfo =
(NSMutableDictionary*)objc_unretainedObject(CFDictionaryGetValue(yhendused, (__bridge void *)connection));
[[connectionInfo objectForKey:#"receivedData"] appendData:data];
}
-(void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:#"Ühenduse viga" message:#"Kõige tõenäolisemalt on kaardiserveril probleeme või puudub seadmel internetiühendus" delegate:self cancelButtonTitle:#"Sulge" otherButtonTitles:nil];
[alert show];
CFRunLoopStop(CFRunLoopGetCurrent());
}
-(void)connectionDidFinishLoading:(NSURLConnection *)connection
{
NSMutableDictionary *connectionInfo =
(NSMutableDictionary*)objc_unretainedObject(CFDictionaryGetValue(yhendused, (__bridge void *)connection));
[connectionInfo objectForKey:#"receivedData"];
andmedServerist=[connectionInfo objectForKey:#"receivedData"];
_kaardiPilt = [UIImage imageWithData: andmedServerist];
CFDictionaryRemoveValue(yhendused, (__bridge void *)connection);
CFRunLoopStop(CFRunLoopGetCurrent());
}
EDIT: added this:
- (void)viewDidLoad
{
[super viewDidLoad];
Ymin=365000;
Ymax=740000;
Xmin=6375000;
Xmax=6635000;
[self looYhendus];
UIImage *saadudPilt=_kaardiPilt;
imageView=[[UIImageView alloc] initWithImage:saadudPilt];
imageView.frame=CGRectMake(0,0,1024,748);
[_scrollView addSubview:imageView];
[_scrollView setContentSize: CGSizeMake(1024, 748)];
_scrollView.minimumZoomScale = 1.0;
_scrollView.maximumZoomScale = 50.0;
_scrollView.delegate = self;
}
Why are you explicitly calling CFRunLoopRun(); and stopping it in connectionDidFinishLoading: or didFailWithError: methods ? (CFRunLoopStop(CFRunLoopGetCurrent());)
Assuming you are doing this on main thread. You are stopping mainthread's runloop. There can be timers, ScrollView uses events which stop responding because you stopped the main thread's runloop.
If you are calling NSURLConnection on the main thread you don't need to explicitly run it (or stop it). You can just schedule to run on current runloop which is main threads runloop. If you are doing it on a background thread, then your code seems valid (Although you shouldn't show UIAlertView in didFailWithError: if its called on separate thread).
Updated Answer(Based on #Shiim's comment):
In the viewDidLoad method you are calling [self looYhendus]; which returns immediately (as you are using Asynchronous URL Connection for the load). So its working as expected. Move [scrollView addSubview:imageView] to connectionDidFinishLoading: method which would add your downloaded imageView data to scrollView's subView once finished downloading it. Or you can consider using dispatch_queue's to create a thread and load the URL request synchronously then using dispatch_queue's main queue to dispatch drawing of imageView added as subView to ScrollView onto main thread.
My recommendation in your case would be redesigned approach using dispatch_queue's. Which would be give you better understanding of solving problem (in this scenario) and also improves your code readability.
I had the same problem recently. The issue was that I was putting my connection in an asynchronous thread, when connections are already asynchronous.
I found the solution here: NSURLConnection delegate methods are not called
There are also a few links to other people who had similar issues in that thread.
If I were you though, I would try simply using [theConnection start] and initializing the request with a set timeout so you don't have to worry about the background thread shutting out before the image is downloaded.
For example:
[request setTimeoutInterval:30];
How can I get NSURLConnection to call it's delegate methods from a different thread instead of the main thread. I'm trying to mess around with the scheduleInRunLoop:forMode:but doesn't seem to do what I want.
I have to download a large file and it interrupts the main thread so frequently that some rendering that is happening starts getting choppy.
NSURLRequest * request = [NSURLRequest requestWithURL:url];
NSURLConnection * connection = [[NSURLConnection alloc] initWithRequest:request delegate:self startImmediately:NO];
NSRunLoop * loop = [NSRunLoop currentRunLoop];
NSLog(#"loop mode: %#",[loop currentMode]);
[connection scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSRunLoopCommonModes];
[connection start];
The other thing I don't see much of is "Modes" There are only two modes documented so not much really to test with.
Any ideas?
Thanks
There are several options:
In your implementation of the delegate methods, make use of dispatch_async.
Start the schedule the connection on a background thread.
You can do the latter like this:
// all the setup comes here
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
NSRunLoop *loop = [NSRunLoop currentRunLoop];
[connection scheduleInRunLoop:loop forMode:NSRunLoopCommonModes];
[loop run]; // make sure that you have a running run-loop.
});
If you want a guarantee on which thread you're running, replace the call to dispatch_get_global_queue() appropriately.
If you want to perform downloads on a separate thread, I'm pretty sure these are the droids you're looking for...
- (void) dispatchRequest{
self->finished = NO;
NSMutableURLRequest* request = //Formulate your request
NSThread* download_thread = [[NSThread alloc] initWithTarget:self selector:#selector(downloadThreadLoop:) object:request];
[download_thread start];
}
- (void) downloadThreadLoop:(NSMutableURLRequest*) request{
NSURLConnection* connection = [[NSURLConnection alloc] initWithRequest:request delegate:self];
while(!self->finished]){
//This line below is the magic!
[[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode beforeDate:[NSDate distantFuture]];
}
}
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response{
//...
}
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data{
//...
}
- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error{
//...
}
- (void)connectionDidFinishLoading:(NSURLConnection *)connection{
//...
self->finished = YES;
}
If you truly need to do the download in a new thread, it may be easier to detachNewThreadSelector:toTarget:withObject:, setup (and destroy) an NSAutoreleasePool, and then use one of the synchronous selectors like NSData's dataWithContentsOfURL:. This will not make use of the asynchronous NSURLConnectionDelegate.
Because this call is synchronous, it will not return until the file has been downloaded, which will block the main thread, but because you're in a new thread, it won't. Please note that this is typically discouraged behavior. Is there other code happening in the main thread that can be optimized?
NSURLConnection is already doing the download off of the main thread asynchronously. If I understand your question, you would like the delegate messages to be sent on a thread other than the main thread? You can't do that as you can't modify the internal implementation of NSURLConnection. I can think of two ways to simulate this.
Create a sublcass of NSURLConnection (e.g. MyURLConnection) that assigns itself as own delegate. Note that this creates an intentional retain cycle so be careful. MyURLConnection should define a new delegate that supports NSURLConnectionDelegate. Let's call this finalDelegate. When MyURLConnection handles it's own delegate messages, forward or dispatch them to finalDelegate on whatever thread you like.
Similar to option #1 but without the subclass. Handle the NSURLConnection delegate methods on the main thread and forward/dispatch them to whatever thread you like.
The main difference is if you want a reusable subclass that behaves this way or it's a one off implementation.
EDIT: added suggestion on how to run code in the background
If you are going to process the response in the background I would either use operations or grand central dispatch. No need to mess around with run loops and creating threads. Check out Apple's Concurrency Programming Guide.