i've an app that when start control updates and other things. If the app find some updates they will ask user if this updates have to be done. If user select YES i want that a spinner appear on main screen until update finish. But when i tap YES my alert view doesn't disappear and remain on screen until update is finished.
Is it possible to create a thread that run on the main thread and stop when update in finished?
Thanks
-(void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex {
if (buttonIndex==1) {
[self showActivityViewer];
[self downloadControlAndUpdatePoi];
[self downloadControlAndUpdateItinerari];
[self downloadControlAndUpdateArtisti];
[self downloadControlAndUpdateEventi];
[self hideActivityViewer];
NSLog(#"AGGIORNA");
} else {
NSLog(#"NON AGGIORNARE");
return;
}
}
If the methods
[self downloadControlAndUpdatePoi];
[self downloadControlAndUpdateItinerari];
[self downloadControlAndUpdateArtisti];
[self downloadControlAndUpdateEventi];
are executed synchronously (that means that they return only after having processed completely), so:
[self hideActivityViewer];
is executed only at the very end.
A simple approach to this is scheduling the execution of your methods on the main thread:
[self performSelector:#selector(downloadControlAndUpdatePoi) withObject:nil afterDelay:0];
....
[self hideActivityViewer];
so that those methods are executed only after control has returned to the main loop and the UI has been updated.
Otherwise, you could use:
+ detachNewThreadSelector:toTarget:withObject:
from NSThread, to do more or less the same. In this case I would suggest creating a wrapper method for all of your dowloadAndUpdate... methods, but keep in mind that you can't update the UI from a secondary thread.
In both cases, you should take some care about synchronizing the download... operations with the rest of your workflow after removing the alert view.
Related
I am uploading a picture to a server. I am using a UIAlertView, AlertView1, which asks the user if he/she wants to upload the picture. If Yes, a second alertview, AlertView2 will show with a progress bar and disappear after the upload is complete.
So, once the user clicks on Yes in AlertView1, I call show AlertView2 and call the method [self uploadPhoto]. So the problem comes that even before AlertView2 has time to show up, the CPU intensive uploadPhoto is running and it delays the AlertView2 from showing up for several seconds. It seems like the AlertView2 finally shows a ways through the uploading process.
How do I start the uploading process only once AlertView2 has shown?
Here is the code
- (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex
{
//Detectss AlertView1's buttonClick
[self.alertView2 show];
}
- (void)alertView:(UIAlertView *)alertView didDismissWithButtonIndex:(NSInteger)buttonIndex
{
//Launches when AlertView1 is dismissed
[self UploadPhoto]
}
-(void)uploadPhoto
{
//CPU/Network Intensive Code to Upload a photo to a server.
}
Set your controller as the delegate of the second alert view, and upload the photo when you receive the didPresentAlertView: message from your second alert.
Use multi-threading to dispatch uploadPhoto to another thread. That way you won't block the main thread while performing costly network operations.
dispatch_queue_t queue = dispatch_queue_create("upload queue", NULL);
dispatch_async(queue, ^{
[self uploadPhoto];
dispatch_async(dispatch_get_main_queue(), ^{
//dismiss alertview2 here
});
});
Call your method [self uploadPhoto] after calling [self.alertView2 show] with a timer using -
[self performSelector:#selector(uploadPhoto) withObject:nil afterDelay:0.3];
It will call your method after a 3 seconds gap after your alert appears.
Is there a way in the normal obj-c or cocos2d to make a delay inside a if-else block?
Like
if ([self isValidTileCoord:cTileCoord] && ![self isWallAtTileCoord:cTileCoord])
{
[self addChild:circle0];
//wait two seconds
//perform another task
}
Just a simple lag to wait between two tasks, or stalling an action. Is there any simple way to do this?
There are many ways to do this. I would use GCD
if ([self isValidTileCoord:cTileCoord] && ![self isWallAtTileCoord:cTileCoord])
{
[self addChild:circle0];
//wait two seconds
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, 2 * NSEC_PER_SEC), dispatch_get_current_queue(), ^{
//perform another task;
});
}
You can use the performSelector: withObject: afterDelay: method to delay tasks:
if ([self isValidTileCoord:cTileCoord] && ![self isWallAtTileCoord:cTileCoord])
{
[self addChild:circle0];
//wait two seconds
[self performSelector:#selector(continueTask) withObject:nil afterDelay:2.0];
}
And in the selector method:
-(void)continueTask
{
//perform another task
}
Inside the cocos2d you can also run an Action on the node like,
[self runAction:[CCSequence actions:[CCDelayTime actionWithDuration:2.0],[CCCallFunc actionWithTarget:self selector:#selector(anothertaks)],nil]];
Perform selector will also work but the problem is that all the schedulers of cocos2D get paused when the app go to background but on the other side perform selector will still count the time, so some time it create task,animation,etc syncing problems.
Perform selector:
[self performSelector:#selector(continueTask) withObject:nil afterDelay:2.0];
I have 3 screens on my app.First is login. Second is search and third is process the task.
On login i retrieve data from a web service. It returns data in XML format. So the data is considerably large. So i am doing that task on a background thread like this to stop Mainthread freezing up on me:
-(BOOL)loginEmp
{
.....some computation
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT,
(unsigned long)NULL), ^(void) {
[self getAllCustomerValues];
});
}
-(void)getAllCustomerValues
{
....more computation.Bring the data,parse it and save it to CoreData DB.
//notification - EDIT
NSNotification *notification =[NSNotification notificationWithName:#"reloadRequest"
object:self];
[[NSNotificationCenter defaultCenter] postNotification : notification];
}
//EDIT
//SearchScreenVC.m
- (void)viewDidLoad
{
....some computation
[self.customerActIndicator startAnimating];
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(stopActivityIndicator)
name:#"reloadRequest"
object:nil];
}
- (void)stopActivityIndicator
{
[self.customerActIndicator stopAnimating];
self.customerActIndicator.hidesWhenStopped = YES;
self.customerActIndicator.hidden =YES;
NSLog(#"HIt this at 127");
}
So on condition that login was successful, i move to screen 2. But the background thread is still in process( i know because i have logs logging values) . I want an activity indicator showing up here (2nd screen)telling user to wait before he starts searching. So how do i do it?How can i make my activity indicator listen/wait for background thread. Please let me know if you need more info.Thanks
EDIT: so I edited accordingly but the notification never gets called. I put a notification at the end of getAllCustomerValues and in viewDidLoad of SearchScreen i used it. That notification on 2nd screen to stop animating never gets called. What is the mistake i am doing.?Thanks
EDIT 2: So it finally hits the method. I dont know what made it to hit that method. I put a break point. I wrote to stop animating but it wouldn't. I wrote hidesWhenStoppped and hidden both to YES. But it still keeps animating.How do i get it to stop?
Ok, if it is not the main thread, put the following in and that should fix it.
- (void)stopActivityIndicator
{
if(![NSThread isMainThread]){
[self performSelectorOnMainThread:#selector(stopActivityIndicator) withObject:nil waitUntilDone:NO];
return;
}
[self.customerActIndicator stopAnimating];
self.customerActIndicator.hidesWhenStopped = YES;
self.customerActIndicator.hidden =YES;
NSLog(#"HIt this at 127");
}
Could you put your background operation into a separate class and then set a delegate on it so you can alert the delegate once the operation has completed?
I havent tried this, its just an idea :)
You could use a delegate pointing to your view controller & a method in your view controller like:
- (void) updateProgress:(NSNumber*)percentageComplete {
}
And then in the background thread:
float percentComplete = 0.5; // for example
NSNumber *percentComplete = [NSNumber numberWithFloat:percentComplete];
[delegate performSelectorOnMainThread:#selector(updateProgress:) withObject:percentageComplete waitUntilDone:NO];
the question is simple : my app control if there is an update every time it starts. If there is an update a popup will be shown with a Yes or No choose. When user tap Yes 4 methods start. These methods download xml file and upload CoreData. This is the code of the alert :
-(void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex {
if (buttonIndex==1) {
[self showActivityViewer];
[self downloadControlAndUpdatePoi];
[self downloadControlAndUpdateItinerari];
[self downloadControlAndUpdateArtisti];
[self downloadControlAndUpdateEventi];
[self hideActivityViewer];
NSLog(#"AGGIORNA");
} else {
NSLog(#"NON AGGIORNARE");
return;
}
}
But there is a problem : when user tap Yes the alert doesn't disappear and remain on screen until all methods are finished. So i try this other code :
-(void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex {
if (buttonIndex==1) {
[self showActivityViewer];
[NSThread detachNewThreadSelector:#selector(startDownloads) toTarget:self withObject:nil];
[self hideActivityViewer];
NSLog(#"AGGIORNA");
} else {
NSLog(#"NON AGGIORNARE");
return;
}
}
-(void)startDownloads {
NSInvocationOperation *opPoi=[[NSInvocationOperation alloc] initWithTarget:self selector:#selector(downloadControlAndUpdatePoi) object:nil];
NSInvocationOperation *opItinerari=[[NSInvocationOperation alloc] initWithTarget:self selector:#selector(downloadControlAndUpdateItinerari) object:nil];
NSInvocationOperation *opArtisti=[[NSInvocationOperation alloc] initWithTarget:self selector:#selector(downloadControlAndUpdateArtisti) object:nil];
NSInvocationOperation *opEventi=[[NSInvocationOperation alloc] initWithTarget:self selector:#selector(downloadControlAndUpdateEventi) object:nil];
NSArray *operations=[[NSArray alloc] initWithObjects:opPoi,opItinerari,opArtisti,opEventi, nil];
NSOperationQueue *queue=[[NSOperationQueue alloc] init];
[queue addOperations:operations waitUntilFinished:YES];
[queue waitUntilAllOperationsAreFinished];
}
There is a problem even here : i tap start, but the activity viewer doesn't appear. The alert disappear and the thread start and run the 4 methods one after another.
I need the processes run in background, just like happened with my 2nd code, but i need even my showActityViewer method will be run and show the spinner.
Thanks :)
First things first. You don't need to start 4 operations, since you are already in a secondary thread and do not need that the 4 operations be executed in parallel. You could simply do:
-(void)startDownloads {
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
[self downloadControlAndUpdatePoi];
[self downloadControlAndUpdateItinerari];
[self downloadControlAndUpdateArtisti];
[self downloadControlAndUpdateEventi];
[pool release];
}
Above all, you need define an autorelease pool in startDownloads if you use autorelease in the downloadControl* methods, otherwise I suspect you will have leaks.
As to why the activity indicator does not show up, it depends on the fact that you are calling:
[self hideActivityViewer];
immediately after detach. So, you are showing it and removing it, before event the UI has got the time to update itself. Remove that line from there and rewrite startDownloads like this:
-(void)startDownloads {
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
[self downloadControlAndUpdatePoi];
[self downloadControlAndUpdateItinerari];
[self downloadControlAndUpdateArtisti];
[self downloadControlAndUpdateEventi];
[self performSelectorOnMainThread:#selector(hideActivityViewer) withObject:nil waitUntilDone:NO];
[pool release];
}
Here notice that I am calling into the main thread to hideActivityViewer because only the main thread can safely use UIKit.
EDIT:
I did not know that you were using Core Data in the download methods...
Have a look at Concurrency with Core Data. You will need to tweak a bit your code by at least using a separate managed object context for your secondary thread (I don't know if it is feasible for you to create the moc there).
Also have a look at this tutorial from Cocoa is my Girlfriend.
As an alternative to all that, you could consider doing:
if (buttonIndex==1) {
[self showActivityViewer];
[self performSelector:#selector(startDownloads) withObject:nil afterDelay:0];
NSLog(#"AGGIORNA");
} else {
NSLog(#"NON AGGIORNARE");
return;
}
with:
-(void)startDownloads {
[self downloadControlAndUpdatePoi];
[self downloadControlAndUpdateItinerari];
[self downloadControlAndUpdateArtisti];
[self downloadControlAndUpdateEventi];
[self hideActivityViewer];
}
This does not use threads at all, but I am not sure that the activity viewer will show without any glitch. One more level of hack, if needed, and you could specify a delay in
[self performSelector:#selector(startDownloads) withObject:nil afterDelay:0.1];
I'm using GCD for background downloading in my Tab Bar app.
First step is to do some background downloading in -viewWillAppear: (to setup some basic data before the view is loaded).
Second step is to the rest of the background downloading in -viewDidAppear:
For some reason, the dispatch block in -viewDidAppear: gets called before the dispatch block in -viewWillAppear:.
This only happens once after loading the application for the first time switching to the tab with the GCD background methods. Switching to another tab and then switching back to the tab with the GCD background methods. The third (and all the rest subsequent times) time I'm switching back it's works as expected (-viewWillAppear: firing first and then -viewDidAppear:).
Here are excerpts of my code (-viewWillAppear: and -viewDidAppear:):
-viewWillAppear:
- (void)viewWillAppear:(BOOL)animated {
DLog(#"viewWillAppear method running");
[super viewWillAppear:animated];
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
[[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:YES];
[self setDiskCareerIds:[CareersParser idsFrom:#"disk"]];
[self setDownloadedCareerIds:[CareersParser idsFrom:#"web"]];
DLog(#"diskCareerIds after being set in viewWillAppear: %#", [self diskCareerIds])
DLog(#"downloadedCareerIds after being set in viewWillAppear: %#", [self downloadedCareerIds])
if ([[self downloadedCareerIds] isEqualToArray:[self diskCareerIds]]) {
DLog(#"viewWillAppear: ids equal, loading careers from disk.");
self.careers = [CareersParser loadCareersFromDisk];
dispatch_async(dispatch_get_main_queue(), ^{
[self.table reloadData];
[[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:NO];
});
}
});
//[self downloadData];
}
-viewDidAppear:
- (void)viewDidAppear:(BOOL)animated {
DLog(#"viewDidAppear method running");
[super viewDidAppear:animated];
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
[[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:YES];
if (![[self downloadedCareerIds] isEqualToArray:[self diskCareerIds]]) {
DLog(#"ids not equal, saving careers to disk.");
dispatch_async(dispatch_get_main_queue(), ^{
[self showLoadingView];
});
[CareersParser saveCareersToDisk];
self.careers = [CareersParser loadCareersFromDisk];
}
dispatch_async(dispatch_get_main_queue(), ^{
[self.table reloadData];
[[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:NO];
[self removeLoadingView];
});
});
//[self download3];
//[self downloadData];
}
Check the debug log at Pastie.
Well, you're printing that log message in that first block (the one scheduled in viewWillAppear:) after it has done a bunch of parsing, not when it actually starts executing.
The thing is that global queue is a concurrent queue. So even though you are scheduling that first block first, it's not surprising that it sometimes falls behind the other block which is executing concurrently with it.
One simple answer would be to create a serial queue, and then you'll be sure the first block completes before the second one is executed. That seems to be what you want, right?