I want to update an UISlider according to a notification generated by another singleton class.
sondDuration=audioPlayer.currentItem.asset.duration;
songDurationinSeconds=CMTimeGetSeconds(sondDuration);
[NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:#selector(updateTime:) userInfo:nil repeats:YES];
This is my notofication generation.
According to this how I can update my UISlider in another ViewController Please help me.
You can use Delegate Method For that
Like the given Below:
http://www.roostersoftstudios.com/2011/04/12/simple-delegate-tutorial-for-ios-development/
I think you have to add a NSNotification in your viewcontroller which updates the UISlider
In your viewcontroller
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(receiveSliderUpdate:)
name:#"UpdateSlider"
object:nil];
- (void) receiveSliderUpdate:(NSNotification *) notification
{
// [notification name] should always be #"UpdateSlider"
// unless you use this method for observation of other notifications
// as well.
if ([[notification name] isEqualToString:#"UpdateSlider"])
// do something with your slider
}
In your controller add the code to notify your view controller
[[NSNotificationCenter defaultCenter]
postNotificationName:#"UpdateSlider"
object:self];
Related
I am facing an issue with NSNotificationCenter.
I am not able to send message and receive message using NSNotificationCenter in latest ios 8.4 (XCode 6.4)
Please check the following code:
1) I want to send data using first view controller to another view.
so i have written the following code in first viewcontroller:
When user btn clicked method as following :
- (IBAction)btnClicked:(id)sender
{
[self postNotification];
[self performSegueWithIdentifier:#"asGo" sender:self];
}
-(void)postNotification{
[[NSNotificationCenter defaultCenter] postNotificationName:#"MyNotification" object:self];
}
2) In Second view controller i have added observer in ViewWillApper as following :
-(void) viewWillAppear:(BOOL)animated
{
[super viewWillAppear:YES];
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(eventListenerDidReceiveNotification:)
name:#"MyNotification"
object:nil];
}
-(void)eventListenerDidReceiveNotification:(NSNotification*)txt
{
NSLog(#"i got notfication:");
}
so eventListenerDidReceiveNotification is not called while come on view.
But i am not getting above log while i come on second vc with navigation
As others have noted, NSNotificationCenter doesn't work like a post office. It only delivers notifications if someone actually listens to them at the moment they arrived. This is the reason your eventListenerDidReceiveNotification method is not being called: you add an observer in viewWillAppear, which is called after the segue (I assume that you're using segues because of the performSegueWithIdentifier method in your code) is finished, so it's definitely called after postNotification has been called.
So, in order to pass data via NSNotificationCenter you have to add an observer before you post a notification.
The following code is completely useless and unnecessarily overcomplicated, you shouldn't do anything like that, but since you keep insisting on using a scheme like this, here you go:
//Didn't test this code. Didn't even compile it, to be honest, but it should be enough to get the idea.
NSString * const SOUselessNotificationName = #"MyUselessNotification";
#pragma mark - FIRST VC
#interface SOFirstVC : UIViewController
#end
#implementation SOFirstVC
NSString * const SOasGoSegueIdentifer = #"asGo";
- (IBAction)btnClicked:(id)sender {
[self performSegueWithIdentifier:SOasGoSegueIdentifer sender:self];
}
-(void)postNotification {
[[NSNotificationCenter defaultCenter] postNotificationName:SOUselessNotificationName object:self];
}
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
if ([segue.identifer isEqualToString:SOasGoSegueIdentifer]) {
SOSecondVC *destinationVC = (SOSecondVC *)segue.destinationViewController;
[destinationVC registerToReceiveNotificationsFromObject:self];
[self postNotification];
}
}
#end
#pragma mark - SECOND VC
#interface SOSecondVC : UIViewController
-(void)registerToReceiveNotificationsFromObject:(id)object;
#end
#implementation SOSecondVC
-(void)registerToReceiveNotificationsFromObject:(id)object {
[[NSNotificationCenter defaultCenter] addObserver:self selector:(eventListenerDidReceiveUselessNotification:) name:SOUselessNotificationName object:object];
}
-(void)eventListenerDidReceiveUselessNotification:(NSNotification*)uselessNotification {
NSLog(#"I got a useless notfication! Yay!");
}
-(void)dealloc {
[[NSNotificationCenter defaultCenter] removeObserver:self];
}
#end
NSNotificationCenter basically has 3 steps
Adding Observer like [[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(open:) name:#"OpenDetail" object:nil];
Posting Notification [[NSNotificationCenter defaultCenter] postNotificationName:#"OpenDetail" object:self];
Removing Observer [[NSNotificationCenter defaultCenter] removeObserver:self name:#"OpenDetail" object:nil];
I think you are posting your notification and then later adding observer while it's vie versa. You have to add observer first then post notification.
HTH
First you have to setup the data you want to send
NSDictionary *userInfo = [NSDictionary dictionaryWithObject:myObject forKey:#"aKey"];
Then you post it with the data like so:
[[NSNotificationCenter defaultCenter] postNotificationName: #"MyNotification" object:nil userInfo:userInfo];
And finally you read the data off the notification:
-(void)eventListenerDidReceiveNotification:(NSNotification*)notification
{
NSLog(#"i got notification:");
NSDictionary *userInfo = notification.userInfo;
NSString *myObject = [userInfo objectForKey:#"aKey"];
}
I have in my app a UITableview Controller, a View Controller and I'm trying to pass NSDictionary from UITableview Controller to my ViewController, using NSNotificationCenter. So, I push a notification at my UITableview Controller and then I add an observer ,using a selector at my ViewController.The selector is called,but I have an NSLog and get memory results ,like :
ViewController: 0x8a0bcc0
I have tried to pass NSString instead of NSDictionary , but I get again memory results , and not the value of the string.
My code :
UITableView Controller
NSString *string=#"This is a test string";
[[NSNotificationCenter defaultCenter] postNotificationName: #"Update" object: string];
ViewController
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(incomingNotification:) name:#"Update" object:nil];
[[NSNotificationCenter defaultCenter] postNotificationName:#"Update" object:self];
And here is the incomingNotification selector method:
-(void) incomingNotification : (NSNotification *)notification{
NSLog(#"Trying to print : %#",[notification object]);
}
All Notifications take place at ViewDidLoad method.Thank you!
UPDATE
Finally , I quit using NSNotificationCenter and used properties to pass data ,changing a bit the inheretence from my TableViewController. No idea why Notifications did not work ,as they were supposed to. Thank you all ,very much for your suggestions and ideas :)
[[NSNotificationCenter defaultCenter] postNotificationName:#"Update" object:self]
Object means the object that generates a notification. To post parameters use another method
[[NSNotificationCenter defaultCenter] postNotificationName:#"Update" object:self userInfo:string]
If I understand correctly, UIViewController is shown after you tap a button on UITableViewController. And you if you are adding a ViewController as observer in its -viewDidLoad:, then it will be able to receive notifications only when it is loaded.
What do you need:
1) override -init or -initWithNibName: method of ViewController like this:
-(id) init
{
self = [super init];
if (self)
{
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(incomingNotification:) name:#"Update" object:nil];
}
return self;
}
so you can be sure ViewController is observing for notifications from the beginning (well, this might be unnecessary step for your case)
2) when you push ViewController you need to send a notification after it was created, like this:
-(void) tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
ViewController *nextController = [[ViewController alloc] initWithNibName:nil bundle:nil];
[self.navigationController pushViewController:nextController animated:YES];
NSString *string=#"This is a test string";
[[NSNotificationCenter defaultCenter] postNotificationName: #"Update" object: string];
}
However, if you're trying just to send some parameters from one view controller to another, this is the wrong way. Just create a property in ViewController and in method -tableView:didSelectRowAtIndex: of UITableViewController set this property
I'm trying to make my timer "run" in the background by saving the time to disk on entering background and retrieving it on entering foreground. Each view controller has a timer and a timeInterval specified by the user. The problem is, I don't know how to access the timeInterval variable. I think I can get the difference of time by using something like this (would this work?):
NSTimeInterval idleTime = [dateReturnedToForeground timeIntervalSinceDate:dateEnteredBackground];
NSTimeInterval elapsedTime = [[NSDate date] timeIntervalSinceDate:startDate];
elapsedTime -= idleTime;
Each view controller (and timer/time interval) is accessed like this:
-(void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath{
DetailViewController *detailVC;
if (![self.detailViewsDictionary.allKeys containsObject:indexPath]){
detailVC = [[DetailViewController alloc]initWithNibName:#"DetailViewController" bundle:nil];
[self.detailViewsDictionary setObject:detailVC forKey:indexPath];
detailVC.context = self.managedObjectContext;
}else{
detailVC = self.detailViewsDictionary[indexPath];
}
Tasks *task = [[self fetchedResultsController] objectAtIndexPath:indexPath];
detailVC.testTask = task;
[[self navigationController] pushViewController:detailVC animated:YES];
NSLog(#"%#", self.detailViewsDictionary);
[[NSNotificationCenter defaultCenter] addObserver:detailVC forKeyPath:self.detailViewsDictionary[indexPath] options:nil context:nil];
}
I am adding each view controller to the Notification Center so it can be accessed in the app delegate (i think this is right?). Problem is, I don't know how to combine the first code with the view controller code, because I can't access the view controller's properties in the app delegate. Any suggestions so that I can make my timer "run" in the background?
You are going about this all wrong. There is no need to do any of this in the app delegate.
Have each view controller listen for the UIApplicationWillResignActiveNotification notification. Then each view controller can do whatever it feels is appropriate to save its data when the notification is received.
Update:
In the view controller's init... method, register for the notification:
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(resigningActive) name:UIApplicationWillResignActiveNotification object:nil];
In the view controller's dealloc method, unregister:
- (void)dealloc {
[[NSNotificationCenter defaultCenter] removeObserver:self name:UIApplicationWillResignActiveNotification object:nil];
}
Then implement the resigningActive method:
- (void)resigningActive {
// The app is resigning active - do whatever this view controller needs to do
}
I totally understand if they are, but what I'm looking for is a timer that pauses when the application enters the background and unpauses after the user returns to the app. I do not need a background task; I just want to make sure that after approximately x minutes within the app a certain action occurs whether that is today or tomorrow.
Thanks!
Brett
Backgrounding the app (assuming you have no background task) doesn't "pause" the timer. It's still counting down in theory so if the app is reopened, it will fire if enough time has passed. This goes for NSTimer's as well. (Let me know if you want more details as to why and I'll edit the answer).
Consider using the following code:
#implementation MyCustomClass {
int elapsedTime;
NSTimer *timer;
}
- (id) init {
if ( ( self = [super init] ) ) {
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(applicationEnteredBackground)
name:UIApplicationDidEnterBackgroundNotification
object:nil];
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(applicationEnteredForeground)
name:UIApplicationDidBecomeActiveNotification
object:nil];
}
return self;
}
- (void) applicationEnteredForeground {
timer = [NSTimer timerWithTimeInterval:1
target:self
selector:#selector(timerTicked)
userInfo:nil
repeats:YES];
[[NSRunLoop mainRunLoop] addTimer:timer forMode:NSRunLoopCommonModes];
}
- (void) applicationEnteredBackground {
[timer invalidate];
}
- (void) timerTicked {
elapsedTime += 1;
// If enough time passed, do something
}
I want to show a full page image Ad every time a UIViewController is shown.
I think I have to call the method inside a viewDidAppear or ViewWillAppear, but they are being called once.
- (void) viewDidAppear:(BOOL)animated{
[self showAds];
}
- (void) showAds{
//Do Something
}
What should I do to call a method every time a uiviewcontroller is shown( even if its already created)?
ViewWillAppear will be called every time a UIViewController is shown，but won't be called when the app is back to foreground.
you can use Notification to achieve your goal by following code,
This scenario is specially when your app is in background and user press HOME button to active it.
Register for Notifcation when your application enterForground in viewDidLoad only.
[[NSNotificationCenter defaultCenter] addObserver: self
selector: #selector(handleEnteredBackground)
name: UIApplicationDidBecomeActiveNotification
object: nil];
write a method to invoke when application enterForground
-(void)handleEnteredBackground
{
NSLog(#"%s",__FUNCTION__);
// Your stuff here
}
Dont forget to Remove Observer in viewDidUnload method
[[NSNotificationCenter defaultCenter] removeObserver:self];
Post New Notification everytime your application enterForground
- (void)applicationWillEnterForeground:(UIApplication *)application
{
[[NSNotificationCenter defaultCenter] postNotificationName:UIApplicationDidBecomeActiveNotification object:nil];
}
ViewWillAppear should be called every time. Use:
- (void) viewWillAppear:(BOOL)animated{
[self showAds];
}