In the simulator I'm using ZBarCameraSimulator to load a picture with a qrcode in it.
This never invokes the delegate method though
- (void) readerView:(ZBarReaderView*)view
didReadSymbols:(ZBarSymbolSet*)syms
fromImage:(UIImage*)image
ZBarReader works fine on an actual device though - is there something i'm overlooking about using ZBarCameraSimulator?
Related
a quick question for any of you who might have an idea:
I recently encounter a bug in on of my app, and that have raised a little question.
The bug was caused by a piece of code trying to access to an array not yet set.
The funny buisness here was that the same code worked absolutely fine on an iPad Air, and crashed on an iPad Pro.
Indeed, i was trying to access the array in the collectionView:cellForItemAtIndexPath: method of my controller, and the array was initialized in the viewWillAppear: method of the same controller.
In any device that i have tried, exepted on the iPad Pro, the collectionView:cellForItemAtIndexPath: method was always called after the viewWillAppear:, but on the iPad Pro, it is the other way.
I easily fixed the issue, but i'm still wondering why the iPad Pro have a different cycle than the other. Anyone have a clue about that?
(I'm on Objective-C, iOS 11.0)
Change the collectionView:cellForItemAtIndexPath method for conditions like following
if (array has data || data is downloading) {
show activity indicator
} else {
show data
}
Reload collection view when data loads
Following a tutorial exactly, I created files that extend UITableViewController. The problem is that his uitableviewcontroller.m files is filled with pre written code (like the viewDidLoad), while mine is completely blank! Both our uitableviewcontroller.h files all have the code of
#import <UIKit/UIKit.h>
#interface ChemTable : UITableViewController
#property (strong,nonatomic)NSMutableArray *Chemarray;
#end
For learning purpose the auto-generated method are of least use(its perfectly ok even if You remove it). even you can create app without them....."viewDidLoad" is the one very necessary method that runs when the view is loaded, but when you go for real apps you will surely use some of auto-generated methods.
Extra -->I think you also also should see this:
ViewDidLoad - Called when you create the class and load from xib. Great for initial setup and one-time-only work
ViewWillAppear - Called right before your view appears, good for hiding/showing fields or any operations that you want to happen every time before the view is visible. Because you might be going back and forth between views, this will be called every time your view is about to appear on the screen
ViewDidAppear - Called after the view appears - great place to start an animations or the loading of external data from an API.
ViewWill/DidDisappear - Same idea as the WillAppear.
ViewDidUnload/Dispose - Available to you, but usually not necessary in Monotouch. In objective-c, this is where you do your cleanup and release of stuff, but this is handled automatically so not much you really need to do here.
Of the many problems I've been having with my current app, this is one of the most annoying.
In the simulator the login dialog works fine, however on a device it's just a frozen white box and the console prints the following:
void SendDelegateMessage(NSInvocation*): delegate
(webView:resource:willSendRequest:redirectResponse:fromDataSource:)
failed to return after waiting 10 seconds. main run loop mode: kCFRunLoopDefaultMode
I've looked this up but I'm still not sure what it means.
If I try switching
[self authorizeWithFBAppAuth:NO safariAuth:NO];
to
[self authorizeWithFBAppAuth:NO safariAuth:YES];
it switches to the safari app to verify but this somehow kills my app with an error which says ReturnNotPermittedKillClient.
Has anyone experienced a similar problem? On my last app it just worked without any of these issues, and as far as I can see I've done everything the same way this time. However this project was inherited from someone else so there may be underlying causes that I am not aware of.
Edit: Just tried moving the login request from didFinishLaunchingWithOptions to a point in the intro screen class where everything else has already been loaded, just in case it was a memory issue caused by too many tasks trying to run at the same time. This time the error message didn't appear, however the login box still remained white and then closed the app a few seconds later.
Edit2: Seems like it's simply a memory error. I changed all variables which I had previously released to be retained, which has fixed the problem on my 3GS. However on my iPad 1 the problem persists. Incidentally, when changing shouldAutorotateToInterfaceOrientation from using landscaperight to using landscaperight or landscapeleft, when I rotate the iPad I get a memory warning and then the same crash. In both cases there are no debug error messages other than the memory warning, and the app just closes down - there is no breakpoint etc to see where the issue lies.
if you are using the webview then we need to do this first b4 moving to next view .delegate = nil;
This might be what you want:
There are other branches of this in NSObject in the documentation.
Code:
[self performSelector: withObject: afterDelay: ]
The problem was simply down to memory. After changing the way it loads images, sounds etc the problem has gone away.
I am playing some short sounds on my iPad like so: Play a short sound in iOS
I am using a caf file which I can successfully play from the Finder. Now I went through quite a bit of a hassle trying to achieve the playback of the sound and I am curious what might be the problems which I don't seem to understand:
Option 1: When I create the SystemSoundID and then play it right away I don't hear anything on the device and the simulator.
Option 2: When I create an instance variable for the SystemSoundID and initialize it in viewDidLoad I manage to play sound but only on the iPad, not the Simulator.
Option 3: Instead of using SystemSoundID I can also use AVAudioPlayer to playback a .wav file which then works on both the iPad and the Simulator but here I need to create the AVAudioPlayer in viewDidLoad otherwise I won't get any sound if I do everything in one go.
The best option currently seems to be Option 3 because it works on both the Simulator and the iPad, but because I need to pre-initialize the Player I would need an AVAudioPlayer instance for every different sound that I want to play, which does not seem to be very memory-wise...
Is there something that I am missing and is it possible to play sounds on both platforms using the AudioToolbox framework (Option 1 & Option 2)
I wrote a library to simplify all this. It wraps AVAudioPlayer, and works fine on both the device and simulator.
https://github.com/nicklockwood/SoundManager
The code is fairly straightforward, although I do some semi-clever stuff to initialise the audio player. If you don't want to use the library you can just copy the code.
A word of warning though - the simulator throws some odd exceptions internally whenever you use AVAudioPlayer. They don't affect the app at all, but if you have enabled break-on-exceptions in Xcode then the app will drop into the debugger a few times during startup and you'll have to manually resume, which may freak you out if you're not expecting it.
I'm working on a simple proof-of-concept for an iPhone app (and important bit of info, I'm pretty new to Mac OSX development all around). I created a view based app with a timer. I declared my NSTimer in the interface of my app's controller, used #property and #synthesize, and I initialize it in the controller's viewDidLoad method with scheduledTimerWithTimeInterval method. My selector is a method with the signature -(void)someMethod:(NSTimer *)timer which is declared in the interface and defined in the implementation file of the controller as well. I can step past the line where I assign the timer and see that it points to a valid object, but my program goes no further than the end of the viewDidLoad method and never reaches the breakpoint at the first line of my method that is called by the timer. Also, I see GDB: Program received bad signal: "EXC_BAD_ACCESS" in the status bar of xcode at this point (viewDidLoad end is reached). I didn't do anything in IB but add a view and a picker just so I'd see if the UI actually loads...it never does.
So, am I doing something wrong with the NSTimer, or are my troubles elsewhere? How can I use the debugging tools in xcode to get more information?
EXC_BAD_ACCESS usually indicates a memory management error, without seeing the code probably from somewhere else in your app. It's a very common error for beginners, but an important subject to fully understand, so I'd suggest looking through some of the questions on memory management here and find a few guides or tutorials to look through. It's actually pretty easy to learn.
Also, it shouldn't hurt but unless you need to access the timer in between fire events, you don't actually need to store it as an instance variable. Once you create and start a timer it's added to and retained by the application's run loop.
Have you got NSZombieEnabled?
Might be useful if this is failing on an over released object.