UIProgressView update fail with UINotification

Question

I try to solve this problem for several days now I have to ask you...

I've got a View (and a ViewController) with a UITableview. There is a TableViewController for that table which is generated in the ViewController. The TableViewController calls a DataSyncManager sharedInstant object (which is obviously in a separate class) which starts to sync data with the server.

I do it this way (first the refresh method):

-(void) refresh{
    [serverQueueProgressView setProgress:0.0];
    [syncingLabel setAlpha:0.5];
    [serverQueueProgressView setAlpha:1];
    [self performSelector:@selector(reloadTableViewDataSource) withObject:nil afterDelay:1.0];
}

Then the method reloadTableViewDataSource (of TableViewController) is called:

- (void)reloadTableViewDataSource
{
    [dataSyncManager getEntriesFromServer];
}

dataSyncManager is my sharedInstance.

In the getEntriesFromServer method of dataSyncManager I do the loop with different sync items and call everytime

[[NSNotificationCenter defaultCenter]
     postNotificationName:@"ServerQueueProgress"
     object:progress];

with the proper progress as NSNumber (that part works well). The message is now sent and catched by my ViewController (it works, I checked with a breakpoint, it also gets the right progress-NSNumber and converts it to float):

- (void)serverQueueProgress:(NSNotification *)notification {
    if(![NSThread isMainThread])
    {
        [self performSelectorOnMainThread:_cmd withObject:notification waitUntilDone:NO];
        return;
    }

    [queueProgressView setProgress:[[notification object] floatValue]];
}

This is one solution which I found here on stackoverflow. But the if is always skipped because obviously I'm on main thread.

Unfortunately the UIProgressview doesn't get updated, it just hangs around, but I connected it well in Interface Builder (I checked that by setting the progress in another method of ViewController.

I also tried to catch the Notification with my TableViewController and put in some other solutions, but no chance, the UIProgressView doesn't get updated live. Only after the sync is done.

Here is the mentioned code in TableViewController which also gets executed without errors (I also stepped it to make sure every line gehts executed well):

This is the method called when received a the notification:

- (void)serverQueueProgress:(NSNotification *)notification {
    [self performSelectorOnMainThread:@selector(updateProgress:) withObject:[notification object] waitUntilDone:NO];

    [serverQueueProgressView setProgress:[[notification object] floatValue]];
}

Which also calls updateProgress: of the same class:

- (void)updateProgress:(NSNumber *)newProgressValue {
    [serverQueueProgressView setProgress:[newProgressValue floatValue]];
}

No chance. I tried many ways and implemented some in parallel as you see, but the ProgressView won't get updated live. Only at the end of syncing. What am I doing wrong??

EDIT: Here is my getEntriesFromServer and some other stuff in DataSyncManager:

- (void)getEntriesFromServer
{
    [[NSNotificationCenter defaultCenter]
     postNotificationName:@"SynchingStarted"
     object:nil];

    [self completeServerQueue];
    ...
}

and completeServerQueue is the function which sends messages to my ViewController with the proper progress float value (it's only a dummy for loop, which gets executed properly... I've checked it):

- (void)completeServerQueue {  
    NSNumber *progress = [[NSNumber alloc] init];
    for (int i=0; i<15; i++) {
        progress = [[NSNumber alloc] initWithFloat:(100/15*i) ];

        [[NSNotificationCenter defaultCenter]
         postNotificationName:@"ServerQueueProgress"
         object:progress];

        sleep(1);
    }
}

score 0 · Answer 1 · answered Apr 10 '11 at 00:44

0

my guess is the problem isn't the code you've shown here, but other code in getEntriesFromServer. Are you using NSURLConnection? Something like:

NSURLConnection *connection = [[NSURLConnection alloc] initWithRequest:request delegate:self];

then you will get callbacks asynchronously that you can use to update your progress view.

answered Apr 10 '11 at 00:44

ax123man

578
5
17

Thanks for your comment but I'm not using NSURLConnection. I edited my starting question and added getEntriesFromServer and some additional relevant code. Any suggestions how I could do it right? I simply don't have a clue how I should manage it. – tamasgal Apr 10 '11 at 10:15
you have some other problems I see. You use "postNotificationName" but you never register for the notifications with "addObserver". Also, the "object" you pass to postNotificationName should be a dictionary that contains your NSNumber. Read up on NSNotificationCenter and/or check out one of the sample code projects in help. – ax123man Apr 11 '11 at 14:00
The notification is catched fine, as I wrote. I simply didn't post that code because it works. – tamasgal Apr 11 '11 at 15:08
ok, got that (sorry) but I think you still need to change how you are passing "progress" back on the notification. The "object" parameter is the object posting the notification. If you want to send any data back you need to use "postNotification:object:userInfo" and put "progress" in the userInfo dictionary. – ax123man Apr 11 '11 at 21:05

score 0 · Accepted Answer · answered Apr 11 '11 at 14:04

also, when you're having trouble, break the problem down a bit. Instead of:

[serverQueueProgressView setProgress:[[notification object] floatValue]];

do this;

float prog = [notification object] floatValue];
[serverQueueProgressView setProgress:prog];

then debugging would give a clue that this isn't working.

UIProgressView update fail with UINotification

2 Answers2