We are using a UInavigationController with one of the views being one that plays soundtracks.
We are using the AVfountation framework.
We navigate to audiolist(where music is played) on button click
-(IBAction)audioBtnClicked
{
audiolist *audio=[[audiolist alloc] initWithNibName:#"audiolist" bundle:nil];
[self.navigationController pushViewContrller:audio animated:YES];
[audiolist release];
}
When the user plays music and navigates away, the music continues playing
Problem: when the user navigates back to the list of songs and plays another track,
2 songs are playing at the same time.
We think that a new instance of audiolist is created everytime the user navigates back.
We would like to only have one instance of audiolist. How do we make the first instance of audiolist persistent and how do we refer back to it?
You have to do
[audio release];
and not
[audiolist release];
audiolist seems to be your class name. The naming conventions says that classes should be capital and camel-cased, so it should be AudioList. It'll make your code more readable.
To have one single shared instance of your AudioList, you could do this:
Add a class method to your header:
+ (AudioList *) sharedInstance;
then add this to your implementation file:
#implementation AudioList
static AudioList *gSharedInstance = nil;
+ (AudioList *) sharedInstance {
if (gSharedInstance == nil) {
gSharedInstance = [[AudioList alloc] init];
}
return gSharedInstance;
}
Now you can always access that instance with
[AudioList sharedInstance];
Cheers.
Create a singleton AudioManager class that handles all your music playback. When you navigate to that view controller, grab the shared instance of that AudioManager to do whatever you do in that view.
You don't want the view to persist as that would be bad separation of MVC.
Apple has some discussion of different design patterns and their objective-c implementations, including the singleton:
http://developer.apple.com/library/ios/documentation/Cocoa/Conceptual/CocoaFundamentals/CocoaDesignPatterns/CocoaDesignPatterns.html#//apple_ref/doc/uid/TP40002974-CH6-SW6
Related
REVISED...
The crux of the app is communicating with a database server. Responses from the server to the app are all in XML. There are several screens. Example, screen 1 lists the user's information, screen 2 lists the user's past trades, allows new trades, and so on.
Here is some code from my AppDelegate:
StartViewController *svc = [[StartViewController alloc] init];
TradeViewController *tvc = [[TradeViewController alloc] init];
CashViewController *cvc = [[CashViewController alloc] init];
ComViewController *covc = [[ComViewController alloc] init];
PrefsViewController *pvc = [[PrefsViewController alloc] init];
NSMutableArray *tabBarViewControllers = [[NSMutableArray alloc] initWithCapacity:5];
UITabBarController *tabBarController = [[UITabBarController alloc] init];
UINavigationController *navigationController = [[UINavigationController alloc] initWithRootViewController:svc];
[tabBarViewControllers addObject:navigationController];
navigationController = nil;
navigationController = [[UINavigationController alloc] initWithRootViewController:tvc];
[tabBarViewControllers addObject:navigationController];
navigationController = nil;
navigationController = [[UINavigationController alloc] initWithRootViewController:cvc];
[tabBarViewControllers addObject:navigationController];
navigationController = nil;
navigationController = [[UINavigationController alloc] initWithRootViewController:covc];
[tabBarViewControllers addObject:navigationController];
navigationController = nil;
navigationController = [[UINavigationController alloc] initWithRootViewController:pvc];
[tabBarViewControllers addObject:navigationController];
navigationController = nil;
[tabBarController setViewControllers:tabBarViewControllers];
[[self window] setRootViewController:tabBarController];
self.window.backgroundColor = [UIColor whiteColor];
[self.window makeKeyAndVisible];
Trying to stick with the MVC style, I have a singleton class which does all of the "processing".
Now an example on how I run into a wall… the user can change their email address on screen 5. Enter new email address into text field and click the save button. The button then calls a method from the singleton class which sends the new email address to the server and (via the URL) and receives a XML response confirming the change.
Here are my problems:
1. I start the spinner from the view controller before I make the singleton class method call - but not knowing when the app to server send/receive is finished, how do I make the spinner stop at the right time? I can't of it from the singleton class, I tried that. From what I know, it has to be from within the VC or is there a way to change VC output from my singleton class?
The singleton class NSURLConnection is handling ALL of my communication. Everything from a simple, email change all the way to updating transaction tables. This just seems wrong to me and makes it very difficult to keep track on who is calling what. Again, I am going by my interpretation of MVC. I think it would be much easier to have a NSURLConnection for every VC and do some processing in those classes. However that would not be MVC(ish).
I have close to a 100 variables, arrays, etc… in my singleton class which I use to assign values to all my VC. This also seems wrong to me but I can't think of any other way.
how can I distinguish in the NSURLConnection delegate
(connectionDidFinishLoading) which URL call is being made?
Each of the delegate methods (such as -connectionDidFinishLoading:) has a connection parameter that tells you which connection sent the message. A given connection can only load one URL at a time, so there's a one to one correspondence between URLs and connections.
How can I tell outside of "connectionDidFinishLoading" when the download is completed?
That method tells you when the connection is finished. It's up to you to store that information somewhere where it's useful to your app.
Update: Based on what you've added, your "processing" class is your app's model. The rest of the app shouldn't care that each transaction involves a message to the server -- that's the model's business alone. Also, there's no reason that the model has to be a single object (let alone a singleton) -- it can be a group of objects that work together.
So, you might have a class (let's call it Processor) that represents the application's interface to the model (some might even call this a "model controller"). An instance of Processor might create a local database for storing the current local state of the app.You might also have a Transaction class that represents a single transaction with the server. A transaction could create a request, send it to the server, get the response, update the database, and tell the Processor that the transaction is done. Or, maybe when some other part of the app (like one of your view controllers) asks the Processor to process a new transaction, the Processor passes the requesting object along to the transaction that it creates so that the transaction can update the requestor directly.
It's hard to say what the best plan for your app is without knowing where you're planning on taking it, but the usual guidelines hold:
break your problem into parts that are easier to solve
limit the scope of each class's responsibilities
if something seems to complicated, it probably is
Breaking your model up into several classes will make it easier to test, as well. You can imagine how easy it would be to write a set of unit tests for the Transaction class. The same goes for Processor -- if the server transaction stuff is in a different class, it's easier to test that the Processor is doing the right thing.
If you have multiple NSURLConnections for the same delegate, consider using a global (well, let's say rather an instance variable) NSMutableDictionary instance, in which you store the data depending on which NSURLConnection is being called. You can use, for example, the in-memory address of the connections converted to an NSString (something like
[NSString stringWithFormat:#"%p", connection]
should do the trick).
Also, in the connectionDidFinishLoading: and connection:didFailLoadWithError: methods, remove the keys corresponding to the NSURLConnections. Thus, you can tell it from 'outside' if a connection is finished: just check if it is in the dictionary or not.
If you're downloading any data over a network connection, I would suggest using ASIHttpRequest. This will allow you to download files asynchronously, meaning your interface doesn't freeze during the download process.
If you use ASIHttpRequest, you can also set the didFinishSelector. By doing this, you can control which method is called when a specific URL has finished loading.
Have a look at this:
NSURL *url = [NSURL URLWithString:#"http://allseeing-i.com"];
ASIHTTPRequest *request = [ASIHTTPRequest requestWithURL:url];
[request setDelegate:self];
[request startAsynchronous];
[request setDidFinishSelector:#selector(requestDone:)];
Then:
- (void)requestDone:(ASIHTTPRequest *)request
{
// Use when fetching text data
NSString *responseString = [request responseString];
// Use when fetching binary data
NSData *responseData = [request responseData];
// If you want, you can get the url of the request like this
NSURL *url = [request url];
}
As for the second part of your question, if the requestDone: method has not been called, you know the download has not completed.
If you want to do something more complicated with multiple downloads, ASIHttpRequest offers queue functionality too. Take a look here.
Hope this will help you.
- (void)connectionDidFinishLoading:(NSURLConnection*)connection
{
NSString *urlString = [[[connection originalRequest] URL] absoluteString];
if ([urlString caseInsensitiveCompare:#"http://www.apple.com"] == NSOrderedSame) {
//Do Task#1
}
else if ([urlString caseInsensitiveCompare:#"http://www.google.com"] == NSOrderedSame)
{
//Do Task#2
}
}
I would recommend subclassing NSURLConnection. Simply add two properties: an NSInteger, tag, and a BOOL, isFinished. This way, you can #define tags for each different request and then identify them by tag in your delegate methods. In connectionDidFinishLoading, you can set the isFinished BOOL to YES, and then you can check in other methods if then connection is finished.
Here's my own NSURLConnection subclass, TTURLConnection:
TTURLConnection.h:
#import <Foundation/Foundation.h>
#interface TTURLConnection : NSURLConnection <NSURLConnectionDelegate>
#property (nonatomic) NSInteger tag;
#property (nonatomic) BOOL isLocked;
- (id)initWithRequest:(NSURLRequest *)request delegate:(id)delegate startImmediately:
(BOOL)startImmediately tag:(NSInteger)tagParam;
#end
TTURLConnection.m:
#import "TTURLConnection.h"
#implementation TTURLConnection
#synthesize tag;
- (id)initWithRequest:(NSURLRequest *)request delegate:(id)delegate startImmediately:
(BOOL)startImmediately tag:(NSInteger)tagParam {
self = [super initWithRequest:request delegate:delegate
startImmediately:startImmediately];
if(self) {
self.tag = tagParam;
}
return self;
}
#end
I am writing my first comprehensive app using Core Data, and I want to see what the best way to keep track of various object changes / updates / deletes is. For example, I have a Notes entity and a Location entity, and a one-to-one relationship between them, the idea being that each note could have its location tagged. I then have a UITableView with a fetchedResultsController driving the list of notes (where you can add new notes and attach a date and location to them), but then I have 2 other view controllers, one with a map view and one with a calendar view. The map view fetches all the locations in Location and displays them on a map. The calendar view basically gets all the data from Notes again and just shows it in a calendar view.
How should I keep track of changes to Notes and Location in my calendar and map view? It's easy to load them up once in viewDidLoad, but how should I keep track of all the changes, so that when the user revisits the mapview (for e.g.) he/she sees the latest data as well.
The one way I've deciphered is to listen for notifications in NSManagedObjectContextObjectsDidChangeNotification, in both the maps view and the calendar view. This seems to return all the inserted, deleted and updated objects from a managed context, each time there's a save. I could then go through these objects and see if I need to update my view. This is how I'm thinking of doing it:
In MapViewController viewDidLoad:
[[NSNotificationCenter defaultCenter]
addObserver: self
selector: #selector(objectChangedNotificationReceived:)
name: NSManagedObjectContextObjectsDidChangeNotification
object: context];
Then:
- (void) objectChangedNotificationReceived: (NSNotification *) notification
{
NSArray* insertedObjects = [[notification userInfo]
objectForKey:NSInsertedObjectsKey] ;
NSArray* deletedObjects = [[notification userInfo]
objectForKey:NSDeletedObjectsKey] ;
NSArray* updatedObjects = [[notification userInfo]
objectForKey:NSUpdatedObjectsKey] ;
NSLog(#"insertObjects: %#", [insertedObjects description]);
NSLog(#"deletedObjects: %#", [deletedObjects description]);
NSLog(#"updatedObjects: %#", [updatedObjects description]);
for (NSManagedObject *obj in insertedObjects) {
if ([obj class] == [Location class]) {
NSLog(#"adding a new location");
Location *locationObj = (Location *) obj;
[self.mapview addAnnotation: locationObj];
}
}
}
Does this seem about right? It seems like a lot of redundant code to put into each view controller, especially if I'm interested in more than one NSManagedObject. Is there some other technique that I'm missing?
NSFetchedResultsController seems to fit your requirement. It will efficiently manage the data handling from the Core Data. You reuse the same fetch request for both of your calendar view controller and map view controller.
Why can't you just fetch the latest data directly from CoreData on the viewWillLoad or viewDidLoad method. This will ensure that you have the latest objects.
Seems like that would be more modular and cleaner.
What I want to do is I have many classes first of all, they all have the same music throughout, as i said in the app delegates bool application did finish launching method. But in my last 3 classes, I want different music, fair enough, I put these lines of code:
[(Smart2AppDelegate *)[UIApplication sharedApplication].delegate pauseAudioPlayer];
[(Smart2AppDelegate *)[UIApplication sharedApplication].delegate newAudioPlayer];
And in my app delegate:
-(void)newAudioPlayer {
NSString *music = [[NSBundle mainBundle]
pathForResource:#"win" ofType:#"m4a"];
audio.delegate = self;
self.audio = [[AVAudioPlayer alloc] initWithContentsOfURL:[NSURL fileURLWithPath:music] error:NULL];
[audio play];
audio.numberOfLoops = -1;
}
-(void)pauseAudioPlayer {
[audio pause];
}
So it works, whenever I go to that view, it changes music, lets call that view, view x. Now, from that view x I can go to and from only to 2 other views, e.g. I can go to the info page and there is a back button that leads back to that view x, and the same with a prize page. But when I go back to the view x, the music starts from the beginning, when in these three classes, i want them to all loop and not go from beginning because it sounds akward. The reason is simple it is because I put it in the viewDidLoad. But how can I do this, I was thinking of a way to actually group classes and put in the avaudioplayer method in there.
Here you have a possible approach:
Refactor out the music+sounds mechanisms into a separate class, i.e. something like Smart2AudioPlayer.
Public the necessary methods: play, pause, resume so you can use the audio player from anywhere.
In each viewDidLoad method, call the audio player and pass along a parameter to indicate who is the sender (who wants the sound to be played) and a preference indicating whether you wish to continue playing the current group song (see bellow) or start it all over again.
Implement the necessary logic in your audio player to allow certain groups of classes to be associated together. This way, when you are playing a song from a class that belongs to a group, and another class of the same group asks for the music to be played, you won't start the song again, you simply do nothing.
Hope this helps
In my Iphone application I am trying to navigate from one table view controller to next table view controller. Problem I am facing is that I have to fetch data using http request and then parse this data when the user select a cell. I am able to fetch and parse the data but the view controller is not waiting for the data to parsed and the next view controller is shown (which is empty). How to over come this problem.
indexSelected = [NSString stringWithFormat: #"%d",[indexPath row] ];
[[MySingletonClass sharedMySingleton] doAnAuthenticatedAPIFetch_Subscriber_Detail : indexSelected];
SubscribersDetailViews2 *viewController = [[SubscribersDetailViews2 alloc] initWithNibName:#"SubscribersDetailViews2" bundle:nil];
[[self navigationController] pushViewController:viewController animated:YES];
[viewController release];
This is what you do:
indexSelected = [NSString stringWithFormat: #"%d",[indexPath row] ];
SubscribersDetailViews2 *viewController = [[SubscribersDetailViews2 alloc] initWithNibName:#"SubscribersDetailViews2" bundle:nil];
[[MySingletonClass sharedMySingleton] doAnAuthenticatedAPIFetch_Subscriber_Detail:indexSelected delegate:self];
[[self navigationController] pushViewController:viewController animated:YES];
[viewController release];
You define a protocol that your view controller conforms to and when the fetching and parsing of data is done you call a method on the delegate to let the view controller know that the data is ready to be displayed.
If you need more information on how to do this, leave a comment.
EDIT: So here's how to declare and use a protocol. I'm going to try to keep it as simple as possible. I'm not sure if I like your naming convention, but I'll still use it for this example.
So let's get down to the code. This is how you declare a protocol:
#protocol MySingletonClassDelegate <NSObject>
#optional
- (void)didDoAnAuthenticatedAPIFetch_Subscriber_Detail_WithData:(NSArray *)data;
- (void)failedToDoAnAuthenticatedAPIFetch_Subscriber_Detail_WithError:(NSError *)error;
#end
Again, I'm not too fond of the naming convention. You shouldn't have underscores in objective-c method names.
The protocol should be defined in MySingletonClass.h before the declaration of MySingletonClass.
I declared two methods in the protocol, one for delivering the data and one for delivering an error if it fails, so that you can notify the user that it failed.
To use the protocol you need the following:
#interface SubscribersDetailViews2 : UITableViewController <MySingletonClassDelegate>
You also need to implement the methods declared in the protocol, but I'll leave that implementation to you.
Since the fetching of data already seems to be happening in the background I don't think I'll need to explain how to do that. One important thing to remember is that you want to execute the delegate methods on the main thread. Here's the code to do that:
- (void)doAnAuthenticatedAPIFetch_Subscriber_Detail:(NSUInteger)index delegate:id<MySingletonClassDelegate>delegate {
// Fetching data in background
if (successful) {
[self performSelectorOnMainThread:#selector(didDoAnAuthenticatedAPIFetch_Subscriber_Detail_WithData:) withObject:data waitUntilDone:NO];
} else {
[self performSelectorOnMainThread:#selector(failedToDoAnAuthenticatedAPIFetch_Subscriber_Detail_WithError:) withObject:error waitUntilDone:NO];
}
}
Just to be clear the // Fetching data in background is supposed to be replaced by your code. I assume that your code produces the variables (NSArray *data, NSError *error, BOOL successful) that I use.
That's about it, if you need clarification on anything let me know.
There are a number of options:
Cache the data, i.e., take a full copy of it on the iOS device (may not be practical of course)
Display an interstitial screen saying "loading" and then move to the "real" screen when the data has downloaded
Have, effectively, two different data sources for your table. The first is your current one. The second would be a single cell saying "Loading..."
In short, there's no point and click way of doing this but there's no problem downloading the data on the fly as long as you tell your users what's happening.
Is there a general template or tutorial or web page that describes the procedure for creating a UIPickerview which selects short sound files and plays them upon selection or with a player? Thanks
You'll need a delegate/data-source class for your picker view - something that implements the protocols UIPickerViewDelegate and UIPickerViewDataSource. This can be whatever view controller you've got handling everything else or a separate class - either way, set the UIPickerView's delegate and dataSource properties to your instance of that class.
The class should have three instance variables - an NSArray soundArr to contain the sounds, an NSTimer timer to provide a delay after selection before the sound plays (more on that below), and an AVAudioPlayer audioPlayer to play the selected sound (for which you'll need to import the AVFoundation framework - it's only available in 2.2, as sound playback used to be a lot more complicated).
When you first load the sounds (in your controller class's -init method or whatever), stick 'em in an array along with the title you want them to display, something like this:
NSBundle *bdl = [NSBundle mainBundle];
soundArr = [[NSArray alloc] initWithObjects:[NSDictionary dictionaryWithObjectsAndKeys:#"Sound One",#"title",[NSURL URLWithString:[bdl pathForResource:#"sound1" ofType:#"wav"]],#"url",nil],
[NSDictionary dictionaryWithObjectsAndKeys:#"Sound Two",#"title",[NSURL URLWithString:[bdl pathForResource:#"sound2" ofType:#"wav"]],#"url",nil],
nil];
The methods you'll need to implement are:
-pickerView:numberOfRowsInComponent: - should return the size of soundArr
-pickerView:titleForRow:forComponent: - should return [[soundArr objectAtIndex:row] objectForKey:#"title"]
-numberOfComponentsInPickerView: - should return 1, since you've only got one column (component) to select from
-pickerView:didSelectRow:inComponent: - see below
You don't want the sound to start immediately when the row-selection delegate method gets called, or snippets of sounds will play continuously as the user scrolls the picker. Instead, use a timer with a short delay, something like this:
if(timer != nil)
{
[timer invalidate]; // remove any timer from an earlier selection
timer = nil;
}
timer = [NSTimer scheduledTimerWithTimeInterval:0.4 target:self selector:#selector(startSoundAtURL:) userInfo:[[soundArr objectAtIndex:row] objectForKey:#"url"] repeats:NO]; // and create the new one
Then, implement a -startSoundAtURL: method that sets up the AVAudioPlayer to play that sound:
- (void)startSoundAtURL:(NSURL *)url
{
if(audioPlayer != nil)
{
[audioPlayer stop];
[audioPlayer release];
}
NSError *err;
audioPlayer = [[AVAudioPlayer alloc] initWithContentsOfURL:url error:&err];
if(err != nil)
{
NSLog([err description]);
return;
}
[audioPlayer play];
}
That should pretty much do it.