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• Optimizing drawing on UITableViewCell

  - by Brian

  I am drawing content to a UITableViewCell and it is working well, but I'm trying to understand if there is a better way of doing this. Each cell has the following components: Thumbnail on the left side - could come from server so it is loaded async Title String - variable length so each cell could be different height Timestamp String Gradient background - the gradient goes from the top of the cell to the bottom and is semi-transparent so that background colors shine through with a gloss It currently works well. The drawing occurs as follows: UITableViewController inits/reuses a cell, sets needed data, and calls [cell setNeedsDisplay] The cell has a CALayer for the thumbnail - thumbnailLayer In the cell's drawRect it draws the gradient background and the two strings The cell's drawRect it then calls setIcon - which gets the thumbnail and sets the image as the contents of the thumbnailLayer. If the image is not found locally, it sets a loading image as the contents of the thumbnailLayer and asynchronously gets the thumbnail. Once the thumbnail is received, it is reset by calling setIcon again & resets the thumbnailLayer.contents This all currently works, but using Instruments I see that the thumbnail is compositing with the gradient. I have tried the following to fix this: setting the cell's backgroundView to a view whose drawRect would draw the gradient so that the cell's drawRect could draw the thumbnail and using setNeedsDisplayInRect would allow me to only redraw the thumbnail after it loaded --- but this resulted in the backgroundView's drawing (gradient) covering the cell's drawing (text). I would just draw the thumbnail in the cell's drawRect, but when setNeedsDisplay is called, drawRect will just overlap another image and the loading image may show through. I would clear the rect, but then I would have to redraw the gradient. I would try to draw the gradient in a CAGradientLayer and store a reference to it, so I can quickly redraw it, but I figured I'd have to redraw the gradient if the cell's height changes. Any ideas? I'm sure I'm missing something so any help would be great.

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• Source of UIView Implicit Animation delay?

  - by iPhoneToucher

  I have a block of UIView animation code that looks like this: [UIView beginAnimations:@"pushView" context:nil]; [UIView setAnimationDelay:0]; [UIView setAnimationDuration:.5]; [UIView setAnimationDelegate:self]; [UIView setAnimationWillStartSelector:@selector(animationWillStart)]; view.frame = CGRectMake(0, 0, 320, 416); [UIView commitAnimations]; The code basically mimics the animation of a ModalView presentation and is tied to a button on my interface. When the button is pressed, I get a long (.5 sec) delay (on iPod Touch...twice as fast on iPhone 3GS) before the animationWillStart: actually gets called. My app has lots going on besides this, but I've timed various points of my code and the delay definitely occurs at this block. In other words, a timestamp immediately before this code block and a timestamp when animationWillStart: gets called shows a .5 sec difference. I'm not too experienced with Core Animation and I'm just trying to figure out what the cause of the delay is...Memory use is stable when the animation starts and CoreAnimation FPS seems to be fine in Instruments. The view that gets animated does have upwards of 20 total subviews, but if that were the issue wouldn't it cause choppiness after the animation starts, rather than before? Any ideas?

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• Memory Leak question

  - by franz

  I am having a memory leak issue with the following code. As much as I can tell I don't see why the problem persists but it still does not release when called. I am detecting the problem in instruments and the following code is keeping its "cards" classes alive even when it should had released them. Any help welcome. ... ... -(id)initDeckWithCardsPicked: (NSMutableArray*)cardsPicked andColors:(NSMutableArray*)cardColors { self = [self init]; if (self != nil) { int count = [cardsPicked count]; for (int i=0; i<count; i++) { int cardNum = [[cardsPicked objectAtIndex:i] integerValue]; Card * card = [[MemoryCard alloc] initWithSerialNumber:cardNum position: CGPointZero color:[cardColors objectAtIndex:i]]; [_cards addObject: card]; [card release]; } } return self; } - (id) init { self = [super init]; if (self != nil) { self.bounds = (CGRect){{0,0},[Card cardSize]}; self.cornerRadius = 8; self.backgroundColor = kAlmostInvisibleWhiteColor; self.borderColor = kHighlightColor; self.cards = [NSMutableArray array]; } return self; } ... ...

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• How to write C++ audio processing applications?

  - by cesko82

  Hi everyone, I'm an Electronics and Telecommunications student, next to my graduation. I'm gonna work on a project that involves my knowledge about DSP, music and audio in general. I allready know all the basic mathematic instruments and all the stuff I need to manage it, such as FFT, circular convolution ecc ecc. I want to learn C++ programming basically for one reason: it's very important in the professional world!!! And I think it's one of the most used to write applications working with audio, especially when it's about real time processing. Ok, after this small introduction I would like to know first, which are the most used libraries to work with audio processing in c++?? I was longer looking on the web but i couldn't find a lo of working stuff. (I work under linux with eclipse CDT enviroment). Then I would like to know if there are good sources to learn how to write some working code, such as for example how to write a simple low pass filter. Basically now i will not write real time applications, I would like to start from the processing of a WAV file, or even better an MP3 file, so basically on vectors of samples. Let's say that basically for now I would like to extract the waveform from an audio file, and save it to a thumbnail or to a PNG image. Ok, for now I think it's all I would need. Any ideas, advices, libraries, books, interesting sources about that? Thanks a lot in advance for any kind of answer. Giovanni.

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• Capturing time intervals when somebody was online? How would you impement this feature?

  - by Kirzilla

  Hello, Our aim is to build timelines saying about periods of time when user was online. (It really doesn't matter what user we are talking about and where he was online) To get information about onliners we can call API method, someservice.com/api/?call=whoIsOnline whoIsOnline method will give us a list of users currently online. But there is no API method to get information about who IS NOT online. So, we should build our timelines using information we got from whoIsOnline. Of course there will be a measurement error (we can't track information in realtime). Let's suppose that we will call whoIsOnline method every 2 minutes (yes, we will run our script by cron every 2 minutes). For example, calling whoIsOnline at 08:00 will return Peter_id Michal_id Andy_id calling whoIsOnline at 08:02 will return Michael_id Andy_id George_id As you can see, Peter has gone offline, but we have new onliner - George. Available instruments are Db(MySQL) / text files / key-value storage (Redis/memcache); feel free to choose any of them (or even all of them). So, we have to get information like this George_id was online... 12 May: 08:02-08:30, 12:40-12:46, 20:14-22:36 11 May: 09:10-12:30, 21:45-23:00 10 May: was not online And now question... How would you store information to implement such timelines? How would you query/calculate information about periods of time when user was online? Additional information.. You cannot update information about offline users, only users who are "currently" online. Solution should be flexible: timeline information could be represented relating to any timezone. We should keep information only for last 7 days. Every user seen online is automatically getting his own identifier in our database. Uff.. it was really hard for me to write it because my English is pretty bad, but I hope my question will be clear for you. Thank you.

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• iPhone OS: Strategies for high density image work

  - by Jasconius

  I have a project that is coming around the bend this summer that is going to involve, potentially, an extremely high volume of image data for display. We are talking hundreds of 640x480-ish images in a given application session (scaled to a smaller resolution when displayed), and handfuls of very large (1280x1024 or higher) images at a time. I've already done some preliminary work and I've found that the typical 640x480ish image is just a shade under 1MB in memory when placed into a UIImageView and displayed... but the very large images can be a whopping 5+ MB's in some cases. This project is actually be targeted at the iPad, which, in my Instruments tests seems to cap out at about 80-100MB's of addressable physical memory. Details aside, I need to start thinking of how to move huge volumes of image data between virtual and physical memory while preserving the fluidity and responsiveness of the application, which will be high visibility. I'm probably on the higher ends of intermediate at Objective-C... so I am looking for some solid articles and advice on the following: 1) Responsible management of UIImage and UIImageView in the name of conserving physical RAM 2) Merits of using CGImage over UIImage, particularly for the huge images, and if there will be any performance gain 3) Anything dealing with memory paging particularly as it pertains to images I will epilogue by saying that the numbers I have above maybe off by about 10 or 15%. Images may or may not end up being bundled into the actual app itself as opposed to being loaded in from an external server.

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• How to make a custom NSFormatter work correctly on Snow Leopard?

  - by Nathan

  I have a custom NSFormatter attached to several NSTextFields who's only purpose is to uppercase the characters as they are typed into field. The entire code for my formatter is included below. The stringForObjectValue() and getObjectValue() implementations are no-ops and taken pretty much directly out of Apple's documentation. I'm using the isPartialStringValid() method to return an uppercase version of the string. This code works correctly in 10.4 and 10.5. When I run it on 10.6, I get "strange" behaviour where text fields aren't always render the characters that are typed and sometimes are just displaying garbage. I've tried enabling NSZombie detection and running under Instruments but nothing was reported. I see errors like the following in "Console": HIToolbox: ignoring exception '*** -[NSCFString replaceCharactersInRange:withString:]: Range or index out of bounds' that raised inside Carbon event dispatch ( 0 CoreFoundation 0x917ca58a __raiseError + 410 1 libobjc.A.dylib 0x94581f49 objc_exception_throw + 56 2 CoreFoundation 0x917ca2b8 +[NSException raise:format:arguments:] + 136 3 CoreFoundation 0x917ca22a +[NSException raise:format:] + 58 4 Foundation 0x9140f528 mutateError + 218 5 AppKit 0x9563803a -[NSCell textView:shouldChangeTextInRange:replacementString:] + 852 6 AppKit 0x95636cf1 -[NSTextView(NSSharing) shouldChangeTextInRanges:replacementStrings:] + 1276 7 AppKit 0x95635704 -[NSTextView insertText:replacementRange:] + 667 8 AppKit 0x956333bb -[NSTextInputContext handleTSMEvent:] + 2657 9 AppKit 0x95632949 _NSTSMEventHandler + 209 10 HIToolbox 0x93379129 _ZL23DispatchEventToHandlersP14EventTargetRecP14OpaqueEventRefP14HandlerCallRec + 1567 11 HIToolbox 0x933783f0 _ZL30SendEventToEventTargetInternalP14OpaqueEventRefP20OpaqueEventTargetRefP14HandlerCallRec + 411 12 HIToolbox 0x9339aa81 SendEventToEventTarget + 52 13 HIToolbox 0x933fc952 SendTSMEvent + 82 14 HIToolbox 0x933fc2cf SendUnicodeTextAEToUnicodeDoc + 700 15 HIToolbox 0x933fbed9 TSMKeyEvent + 998 16 HIToolbox 0x933ecede TSMProcessRawKeyEvent + 2515 17 AppKit 0x95632228 -[NSTextInputContext handleEvent:] + 1453 18 AppKit 0x9562e088 -[NSView interpretKeyEvents:] + 209 19 AppKit 0x95631b45 -[NSTextView keyDown:] + 751 20 AppKit 0x95563194 -[NSWindow sendEvent:] + 5757 21 AppKit 0x9547bceb -[NSApplication sendEvent:] + 6431 22 AppKit 0x9540f6fb -[NSApplication run] + 917 23 AppKit 0x95407735 NSApplicationMain + 574 24 macsetup 0x00001f9f main + 24 25 macsetup 0x00001b75 start + 53 ) Can anybody shed some light on what is happening? Am I just using NSFormatter incorrectly? -(NSString*) stringForObjectValue:(id)object { if( ![object isKindOfClass: [ NSString class ] ] ) { return nil; } return [ NSString stringWithString: object ]; } -(BOOL)getObjectValue: (id*)object forString: string errorDescription:(NSString**)error { if( object ) { *object = [ NSString stringWithString: string ]; return YES; } return NO; } -(BOOL) isPartialStringValid: (NSString*) cStr newEditingString: (NSString**) nStr errorDescription: (NSString**) error { *nStr = [NSString stringWithString: [cStr uppercaseString]]; return NO; }

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• Hausman Test, Fixed/random effects in SAS?

  - by John

  Hey guys, I'm trying to do a fixed effecs OLS regression, a random effects OLS Regression and a Hausman test to back up my choice for one of those models. Alas, there does not seem to be a lot of information of what the code looks like when you want to do this. I found for the Hausman test that proc model data=one out=fiml2; endogenous y1 y2; y1 = py2 * y2 + px1 * x1 + interc; y2 = py1* y1 + pz1 * z1 + d2; fit y1 y2 / ols 2sls hausman; instruments x1 z1; run; you do something like this. However, I do not have the equations in the middle, which i assume to be the fixed and random effects models? On an other site I found that PROC TSCSREG automatically displays the Hausman test, unfortunately this does not work either. When I type PROC TSCSREG data = clean; data does not become blue meaning SAS does not recognize this as a type of data input? proc tscsreg data = clean; var nof capm_erm sigma cv fvyrgro meanest tvol bmratio size ab; run; I tried this but obviously doesn't work since it does not recognize the data input, I've been searching but I can't seem to find a proper example of how the code of an hausman test looks like. On the SAS site I neither find the code one has to use to perform a fixed/random effects model. My data has 1784 observations, 578 different firms (cross section?) and spans over a 2001-2006 period in months. Any help?

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• is this uibutton autoreleased ?

  - by dubbeat

  HI This is just a question to check my sanity really. I'm hunting memory leaks that show up in instruments but not the static analyzer. In one spot the analyzer is pointing to this block of code UIButton *randomButton = [UIButton buttonWithType:UIButtonTypeRoundedRect ]; randomButton.frame = CGRectMake(205, 145, 90, 22); // size and position of button [randomButton setTitle:@"Random" forState:UIControlStateNormal]; randomButton.backgroundColor = [UIColor clearColor]; randomButton.adjustsImageWhenHighlighted = YES; [randomButton addTarget:self action:@selector(getrandom:) forControlEvents:UIControlEventTouchUpInside]; [self.view addSubview:randomButton]; For some reason I thought the above code would auto release the button because I'm not calling init or alloc? If I add [randombutton release] at the bottom of the code my button fails to show. Could somebody describe to me the correct way to release a button from memory that is created in the above way? Or would I be better off making the button a class variable and sticking the release in the dealloc method?

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• Memory leak when returning object

  - by Yakattak

  I have this memory leak that has been very stubborn for the past week or so. I have a class method I use in a class called "ArchiveManager" that will unarchive a specific .dat file for me, and return an array with it's contents. Here is the method: +(NSMutableArray *)unarchiveCustomObject { NSMutableArray *array = [NSMutableArray arrayWithArray:[NSKeyedUnarchiver unarchiveObjectWithFile:/* Archive Path */]]; return array; } I understand I don't have ownership of it at this point, and I return it. CustomObject *myObject = [[ArchiveManager unarchiveCustomObject] objectAtIndex:0]; Then, later when I unarchive it in a view controller to be used (I don't even create an array of it, nor do I make a pointer to it, I just reference it to get something out of the array returned by unarchiveCustomIbject (objectAtIndex). This is where Instruments is calling a memory leak, yet I don't see how this can leak! Any ideas? Thanks in advance. Edit: CustomObject initWithCoder added: -(id)initWithCoder:(NSCoder *)aDecoder { if (self = [super init]) { self.string1 = [aDecoder decodeObjectForKey:kString1]; self.string2 = [aDecoder decodeObjectForKey:kString2]; self.string3 = [aDecoder decodeObjectForKey:kString3]; UIImage *picture = [[UIImage alloc] initWithData:[aDecoder decodeObjectForKey:kPicture]]; self.picture = picture; self.array = [aDecoder decodeObjectForKey:kArray]; [picture release]; } return self; }

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• AVAudioPlayer not unloading cached memory after each new allocation

  - by Rob

  I am seeing in Instruments that when I play a sound via the standard "AddMusic" example method that Apple provides, it allocates 32kb of memory via the prepareToPlay call (which references the AudioToolBox framework's Cache_DataSource::ReadBytes function) each time a new player is allocated (i.e. each time a different sound is played). However, that cached data never gets released. This obviously poses a huge problem if it doesn't get released and you have a lot of sound files to play, since it tends to keep allocating memory and eventually crashes if you have enough unique sound files (which I unfortunately do). Have any of you run across this or what am I doing wrong in my code? I've had this issue for a while now and it's really bugging me since my code is verbatim of what Apple's is (I think). How I call the function: - (void)playOnce:(NSString *)aSound { // Gets the file system path to the sound to play. NSString *soundFilePath = [[NSBundle mainBundle] pathForResource:aSound ofType:@"caf"]; // Converts the sound's file path to an NSURL object NSURL *soundURL = [[NSURL alloc] initFileURLWithPath: soundFilePath]; self.soundFileURL = soundURL; [soundURL release]; AVAudioPlayer * newAudio=[[AVAudioPlayer alloc] initWithContentsOfURL: soundFileURL error:nil]; self.theAudio = newAudio; // automatically retain audio and dealloc old file if new m4a file is loaded [newAudio release]; // release the audio safely // this is where the prior cached data never gets released [theAudio prepareToPlay]; // set it up and play [theAudio setNumberOfLoops:0]; [theAudio setVolume: volumeLevel]; [theAudio setDelegate: self]; [theAudio play]; } and then theAudio gets released in the dealloc method of course.

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• howto distinguish composition and self-typing use-cases

  - by ayvango

  Scala has two instruments for expressing object composition: original self-type concept and well known trivial composition. I'm curios what situations I should use which in. There are obvious differences in their applicability. Self-type requires you to use traits. Object composition allows you to change extensions on run-time with var declaration. Leaving technical details behind I can figure two indicators to help with classification of use cases. If some object used as combinator for a complex structure such as tree or just have several similar typed parts (1 car to 4 wheels relation) than it should use composition. There is extreme opposite use case. Lets assume one trait become too big to clearly observe it and it got split. It is quite natural that you should use self-types for this case. That rules are not absolute. You may do extra work to convert code between this techniques. e.g. you may replace 4 wheels composition with self-typing over Product4. You may use Cake[T <: MyType] {part : MyType} instead of Cake { this : MyType => } for cake pattern dependencies. But both cases seem counterintuitive and give you extra work. There are plenty of boundary use cases although. One-to-one relations is very hard to decide with. Is there any simple rule to decide what kind of technique is preferable? self-type makes you classes abstract, composition makes your code verbose. self-type gives your problems with blending namespaces and also gives you extra typing for free (you got not just a cocktail of two elements but gasoline-motor oil cocktail known as a petrol bomb). How can I choose between them? What hints are there? Update: Let us discuss the following example: Adapter pattern. What benefits it has with both selt-typing and composition approaches?

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• Trouble Running Leaks Instrument

  - by TheGeoff

  I'm having trouble running the Leaks Instrument since installing the 3.0 SDK. An NDA disclaimer here I don't think this is a 3.0 SDK issue, just a configuration problem. So I'm looking for advice on configuring the tools in question not the 3.0 SDK per se. Here’s the breakdown of the behavior I am seeing. My Application is compiled to OS version 2.2. I can run it out of XCode in debug mode on the Simulator and Device running 2.2, 2.2.1, 3.0. If I start it with Performance Tools - Leaks, I get an error message from the OS, “The application xxxx quit unexpectedly”, “Ignore, Report, Relaunch.” If I click “Ignore” one of two things will happen, either Leaks tells me it couldn’t attach, or Leaks stop responding to input and I have to Force Quit. Interesting thing is the Simulator starts in 3.0 OS. If I start Instruments Manually and attach to a running 2.2 Simulator it shows the same behavior. If I attach Leaks to an iPhone Device it works. It seems that once I launch Leaks my app won't run in the simulator until I do a new build. Any ideas for getting my Simulator/Leaks/Xcode synced back up? Thanks, Geoff

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• iPhone NSCFString leaks in fetchRequest

  - by camilo

  In the following code: - (NSMutableArray *) fetchNotesForGroup: (NSString *)groupName { // Variables declaration NSMutableArray *result; NSFetchRequest *fetchRequest; NSEntityDescription *entity; NSSortDescriptor *sortDescriptor; NSPredicate *searchPredicate; NSError *error = nil; // Creates the fetchRequest and executes it fetchRequest = [[[NSFetchRequest alloc] init] autorelease]; entity = [NSEntityDescription entityForName:@"Note" inManagedObjectContext:managedObjectContext]; [fetchRequest setEntity:entity]; sortDescriptor = [[[NSSortDescriptor alloc] initWithKey:@"noteName" ascending:YES] autorelease]; [fetchRequest setSortDescriptors:[NSArray arrayWithObject:sortDescriptor]]; [fetchRequest setReturnsDistinctResults:YES]; searchPredicate = [NSPredicate predicateWithFormat:@"categoryName like %@", groupName]; [fetchRequest setPredicate:searchPredicate]; [fetchRequest setPropertiesToFetch:[NSArray arrayWithObject:@"noteName"]]; result = [[managedObjectContext executeFetchRequest:fetchRequest error:&error] mutableCopy]; // Variables release return result; } ... I Fetch notes for a given categoryName. When I'm running Instruments, it says that a NSCFString is leaking. I know leaks are mean for iPhone developers... but I don't have any idea on how to plug this one. Any clues? All help is welcome. Thanks a lot!

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• Which to use, XMP or RDF?

  - by zotty

  What's the difference between RDF and XMP? From what I can tell, XMP is derived from RDF... so what does it offer that RDF doesn't? My particular situation is this: I've got some images which need tagging with details of how an experiment was performed, and what sort of data analysis has been performed on the images. A colleague of mine is pushing for XMP, but he's thinking of the images as photos - they're not really, they're just bits of data. From what I've seen (mainly by opening images in notepad++) the XMP data looks very similar to RDF - even so far as using RDF in the tag names (e.g. <rdf:Seq>). I'd like this data to be usable by other people who use similar instruments for similar experiments, so creating a mini standard (schema?) seems like the way to go. Apologies for the lack of fundemental understanding - I'm a Doctor, not a programmer! If it makes any difference, the language of choice will be C#. Edit for more information: First off, thanks for the excellent replies - thinking of XMP as a vocabulary for RDF makes things a lot clearer. The sort of data I'll be storing wont be avaliable in any of the pre-defined sets. It'll detail experimental set ups, locations and results. I think using RDF is the way to go.

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• iPhone: Leak with UIWebView loading Office documents. Any ideas how to avoid it?

  - by Thomas Tempelmann

  While there are already quite a few posts about leaks around UIWebView, mine is a bit more special, I believe, and thus deserves its own post here. I see a reproducible large leak every time I load a Office document such as a Word or Excel file. For instance, every time I display a 180KB .doc file, I get a 100KB leak. And that happens with both the simulator and an actual device, running OS 3.1.3. The leak is not visible with the Leaks instrument but only by looking at the malloc instances via the ObjectAlloc instrument. Here's a picture from the instruments trace: I've also made a demo project, UIWebView-Leak.zip, so you can verify this yourself. To see the leak, use the ObjectAlloc instrument, switch to the view where you see individual allocation objects, and sort by size so that you see the large ones in a group, just like in my picture above. Then view a Office document a few times and find the Malloc objects that keep staying "Live" even after the actual UIWebView has been freed. Is this a known bug? Or is there any way I can avoid these leaks? I.e, have you successfully shown Office documents on an iPhone withing getting such leaks? Note: I've reported this as a bug to Apple now, too (ID 7950594) I am still waiting for someone (including Apple) to confirm this as a true leak or show why it isn't (i.e. that I do something wrong or make wrong assumptions)

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• Animation is slow on iPhone

  - by Anthony Chan

  I'm developing an app that would display images and change them according to the user's action. I've created a subclass of UIView to contain an image, an index number and an array of image names. The code is like this: @interface CustomPic : UIView { UIImageView *pic; NSInteger index; NSMutableArray *picNames; //<-- an array of NSString } And in the implementation part, it has a method to change the image using a dissolve effect. - (void)nextPic { index++; if (index >= [picNames count]) { index = 0; } UIImageView *temp = pic; pic.image = [UIImage imageNamed:[picNames objectAtIndex:index]]; temp.alpha = 0; [UIView beginAnimations:nil context:nil]; [UIView setAnimationCurve:UIViewAnimationCurveEaseOut]; [UIView setAnimationDuration:0.25]; pic.alpha = 0; temp.alpha = 1; [UIView commitAnimations]; } In the viewController, there are several CustomPic which would change the images depends on users' choice. The images would change as expected with the fade in/out effect, but the animation performance is really bad. I've tested it on an iPhone 3G, the Instruments shows that the animation is only 2-3FPS! I tried many methods to simplify and modify the codes but with no hope. Is there something wrong in my code or in my concept? Thanks for any help. P.S. all the images are 320*480 PNGs with a max size of 15KB.

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• How to remove an object from the canvas?

  - by Marius Jonsson

  Hello there, I am making this script that will rotate a needle on a tachometer using canvas. I am a newbie to this canvas. This is my code: function startup() { var canvas = document.getElementById('canvas'); var context = canvas.getContext('2d'); var meter = new Image(); meter.src = 'background.png'; var pin = new Image(); pin.src = 'needle.png'; context.drawImage(meter,0,0); context.translate(275,297); for (var frm = 0; frm < 6000; frm++){ var r=frm/1000; //handle here var i=r*36-27; //angle of rotation from value of r and span var angleInRadians = 3.14159265 * i/180; //converting degree to radian context.rotate(angleInRadians); //rotating by angle context.drawImage(pin,-250,-3); //adjusting pin center at meter center } } Here is the script in action: http://www.kingoslo.com/instruments/ The problem is, as you can see, that the red needle is not removed beetween each for-loop. What I need to do is to clear the canvas for the pin object between each cycle of the loop. How do I do this? Thanks. Kind regards, Marius

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• JS: Why isn't this variable available to the other functions?

  - by Marius Jonsson

  Hello there, I've am trying to make a canvas animation: var context; var meter; var pin; function init() { var meter = new Image(); var pin = new Image(); var context = document.getElementById('canvas').getContext('2d'); meter.src = 'background.png'; pin.src = 'needle.png'; context.drawImage(meter,0,0); context.translate(275,297); context.save(); setTimeout(startup,500); } function startup() { var r=2; // set rpm here. var i=r*36-27; var angleInRadians = 3.14159265 * i/180; //converting degree to radian context.rotate(angleInRadians); //rotating by angle context.drawImage(pin,-250,-3); //adjusting pin center at meter center context.restore(); } You can see the script at http://www.kingoslo.com/instruments/ With firebug I get error saying that context is undefined, which I think is strange. Thanks. Kind regards, Marius

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• How can I release this NSXMLParser without crashing my app?

  - by prendio2

  Below is the @interface for an MREntitiesConverter object I use to strip all html tags from a string using an NSXMLParser. @interface MREntitiesConverter : NSObject { NSMutableString* resultString; NSString* xmlStr; NSData *data; NSXMLParser* xmlParser; } @property (nonatomic, retain) NSMutableString* resultString; - (NSString*)convertEntitiesInString:(NSString*)s; @end And this is the implementation: @implementation MREntitiesConverter @synthesize resultString; - (id)init { if([super init]) { self.resultString = [NSMutableString string]; } return self; } - (NSString*)convertEntitiesInString:(NSString*)s { xmlStr = [NSString stringWithFormat:@"<data>%@</data>", s]; data = [xmlStr dataUsingEncoding:NSUTF8StringEncoding allowLossyConversion:YES]; xmlParser = [[NSXMLParser alloc] initWithData:data]; [xmlParser setDelegate:self]; [xmlParser parse]; return [resultString autorelease]; } - (void)dealloc { [data release]; //I want to release xmlParser here but it crashes the app [super dealloc]; } - (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)s { [self.resultString appendString:s]; } @end If I release xmlParser in the dealloc method I am crashing my app but without releasing I am quite obviously leaking memory. I am new to Instruments and trying to get the hang of optimising this app. Any help you can offer on this particular issue will likely help me solve other memory issues in my app. Yours in frustrated anticipation: ) Oisin

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• Technology and language for a stable Digital Audio Workstation development

  - by Kill KRT

  Hi, I'm designing a cross platform (Windows/Linux/OS X) application, something like a digital audio workstation. I'd like to create a software where users have a fully featured sequencer (multiple tracks with automation) and where it is possible to create instruments using a visual language (as Pure Data/Max MSP). Ehm... I know that I've already posted a question about a related issue... But in order to decide which technology I should use, I think I'd better to make more investigation. I'm a quite experted user of audio trackers (Renoise, Protracker,...) and sequencers (FL Studio, Cubase 5), but I didn't ever try to develop even a basic audio tracker. I know just the basic theory of mixing sound and know how basically a DSP works. My questions are: Where I can find a good tutorial/guide/book about this issue? Do you think using C# (with NAudio) could dramatically reduce performance? I know C++ would be the best choice, but I find C# so elegant and easy to build and port, while C++ is so powerful and fast, but there are too #define and bad things for my taste! ;-) Thank you.

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• ObjectiveC - Releasing objects added as parameters

  - by NobleK

  Ok, here goes. Being a Java developer I'm still struggling with the memory management in ObjectiveC. I have all the basics covered, but once in a while I encounter a challenge. What I want to do is something which in Java would look like this: MyObject myObject = new MyObject(new MyParameterObject()); The constructor of MyObject class takes a parameter of type MyParameterObject which I initiate on-the-fly. In ObjectiveC I tried to do this using following code: MyObject *myObject = [[MyObject alloc] init:[[MyParameterObject alloc] init]]; However, running the Build and Analyze tool this gives me a "Potential leak of an object" warning for the MyParameter object which indeed occurs when I test it using Instruments. I do understand why this happens since I am taking ownership of the object with the alloc method and not relinquishing it, I just don't know the correct way of doing it. I tried using MyObject *myObject = [[MyObject alloc] init:[[[MyParameterObject alloc] init] autorelease]]; but then the Analyze tool told me that "Object sent -autorelease too many times". I could solve the issue by modifying the init method of MyParameterObject to say return [self autorelease]; in stead of just return self;. Analyze still warnes about a potential leak, but it doesn't actually occur. However I believe that this approach violates the convention for managing memory in ObjectiveC and I really want to do it the right way. Thanx in advance.

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• LINQ : How to query how to sort result by most similarity/equality

  - by aNui

  I want to do a search for Music instruments which has its informations Name, Category and Origin as I asked in my post. But now I want to sort/group the result by similarity/equality to the keyword such as. If I have the list { Harp, Piano, Drum, Guitar, Guitarrón } and if I queried "p" the result should be { Piano, Harp } but it shows Harp first because of the list's sequence and if I add {Grand Piano} to the list and query "piano" the result shoud be like { Piano, Grand Piano } here's my code static IEnumerable<MInstrument> InstrumentsSearch(IEnumerable<MInstrument> InstrumentsList, string query, MInstrument.Category[] SelectedCategories, MInstrument.Origin[] SelectedOrigins) { var result = InstrumentsList .Where(item => SelectedCategories.Contains(item.category)) .Where(item => SelectedOrigins.Contains(item.origin)) .Where(item => { if ( (" " + item.Name.ToLower()).Contains(" " + query.ToLower()) || item.Name.IndexOf(query) != -1 ) { return true; } return false; } ) .Take(30); return result.ToList<MInstrument>(); } Or the result may be like my old self-invented algorithm that I called "by order of occurence", that is just OK to me. Is there any way to do that, please tell me. Thanks in advance.

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• Rapid taps on an OpenGL ES app introducing input delay

  - by Tim R.

  I am starting out writing a 2D game in OpenGL ES, and I have encountered an odd problem: if I rapidly tap the touchscreen, the input starts lagging behind the display. The more times I tap, the more delay it causes between the input and any indication of that input onscreen. It only happens if I intentionally tap very rapidly, but not from tapping and dragging with any number of fingers. What could be causing this? Excessive details follow: Both accelerometer input and taps are delayed by just tapping. The only events I am responding to are touchesBegan (below) in my EAGLView and accelerometer:(UIAccelerometer *)accelerometer didAccelerate:(UIAcceleration *)acceleration in my Game object. There doesn't seem to be any upper limit to the amount of delay: I've gotten up to 12 seconds of delay by tapping rapidly with five fingers. I have not seen any drops in framerate (it stays constantly at 60 fps) in the OpenGL ES tool in Instruments or by taking 1/the time between updates. Possibly relevant code: - (void) drawView:(id) sender { [game update:allTouches]; [renderer render:game]; } -(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event { allTouches = [event allTouches]; } allTouches is a pointer that gets passed to my Game every update, which passes it to each GameObject in their update methods.

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• Memory Leak in returning NSMutableArray from class

  - by Structurer

  Hi I am quite new to Objective C for the iPhone, so I hope you wont kill me for asking a simple question. I have made an App that works fine, except that Instruments reports memory leaks from the class below. I use it to store settings from one class and then retrieve them from another class. These settings are stored on a file so they can be retrieved every time the App is ran. What can I do do release the "setting" and is there anything that can be done to call (use) the class in a smarter way? Thanks ----- Below is Settings.m ----- import "Settings.h" @implementation Settings @synthesize settings; -(NSString *)dataFilePath // Return path for settingfile, including filename { NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); NSString *documentsDirectory = [paths objectAtIndex:0]; return [documentsDirectory stringByAppendingPathComponent:kUserSettingsFileName]; } -(NSMutableArray *)getParameters // Return settings from disk after checking if file exist (if not create with default values) { NSString *filePath = [self dataFilePath]; if ([[NSFileManager defaultManager] fileExistsAtPath:filePath]) // Getting data from file { settings = [[NSMutableArray alloc] initWithContentsOfFile:filePath]; } else // Creating default settings { settings = [[NSMutableArray alloc] initWithObjects: [NSNumber numberWithInteger:50], [NSNumber numberWithInteger:50], nil]; [settings writeToFile:[self dataFilePath] atomically:YES]; } return settings; } ----- Below is my other class from where I call my Settings class ----- // Get settings from file Settings *aSetting = [[Settings alloc] init]; mySettings = [aSetting getParameters]; [aSetting release];

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