Question

I have several subviews that are controlled by a navigation controller. One of them is crashing on resume. It is a class that “rotates” a model 360 degrees (think globe) through advancing a series of images and a pan gesture controller.

All is well and good until I hit that pesky home button. When I hit the home button I have until the image is set on the UIView before it crashes…Most of the time at least. Some times it will change once and crash on the second change apparently just to make my life more interesting.

Any insight you could shed on this would be great.

Thanks in Advance.

//  RotationController.m
//

#import "RotationController.h"

@implementation RotationController

@synthesize myRotationView;
@synthesize imageName;
@synthesize scheme;
int maxFrame;
int currentX;

- (void)viewDidLoad {
    [super viewDidLoad];

    //self.title = @"Cutaway View";

    UIPanGestureRecognizer *panGesture = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(panPiece:)];
    [myRotationView addGestureRecognizer:panGesture];
    [panGesture release];
}

-(void)setup:(int) currentNode{

    if (currentNode <= 2)
    {
        currentX = 0;
        maxFrame = 199;
        scheme = @"Trailer1Rotation_";
        self.title = @"Trailer One Cutaway View";
        [self.myRotationView setImage:[UIImage imageNamed:@"Trailer1Rotation_000.jpg"]];
    }
    else if (currentNode > 2 && currentNode <= 5)
    {
        currentX = 0;
        maxFrame = 199;
        scheme = @"spinTrailer2_00";
        self.title = @"Trailer Two Cutaway View";
        [self.myRotationView setImage:[UIImage imageNamed:@"spinTrailer2_00000.jpg"]];
    }
    else if (currentNode > 5 && currentNode <= 8)
    {
        currentX = 0;
        maxFrame = 199;
        scheme = @"spinTrailer3_00";
        self.title = @"Trailer Three Cutaway View";
        [self.myRotationView setImage:[UIImage imageNamed:@"spinTrailer3_00000.jpg"]];
    }
    else if (currentNode > 8)
    {
        currentX = 0;
        maxFrame = 199;
        scheme = @"spinTrailer4_00";
        self.title = @"Trailer Four Cutaway View";
        [self.myRotationView setImage:[UIImage imageNamed:@"spinTrailer4_00000.jpg"]];
    }
}

-(void)viewWillAppear:(BOOL)animated {

    self.myRotationView.userInteractionEnabled = YES;
}

-(void)applicationDidEnterBackground:(UIApplication *)application
{
    NSLog(@"Test - DidEnterBackGround");
}

-(void)applicationWillResignActive
{
    NSLog(@"Test - WillResignActive");
}

- (void)applicationDidBecomeActive
{
    NSLog(@"Test - DidBecomeActive");

    [self.myRotationView setImage:[UIImage imageNamed:@"Trailer1Rotation_000.jpg"]];
}

-(void)panPiece:(UIPanGestureRecognizer *) gesture{

    switch(gesture.state) {
        case UIGestureRecognizerStateChanged: {
            //CGPoint center = gesture.view.center;
            CGPoint translation = [gesture translationInView:gesture.view];

//          center = CGPointMake((center.x + translation.x),
//                               (center.y + translation.y));
//          gesture.view.center = center;
//          [gesture setTranslation:CGPointZero inView:gesture.view];

            NSLog(@"Changed");
            NSLog(@"%f", translation.x);
            NSLog(@"%f", translation.y);

            int changeX = (int)translation.x / 20;

            if (changeX == 0)
                changeX = 1;

            currentX = (int)currentX + (int)changeX;

            while (currentX > 174) {
                currentX = currentX - 174;
            }

            while (currentX < 0) {
                currentX = currentX + 174;
            }

            if (currentX < 10) {
                imageName = [NSString stringWithFormat:@"%@00%i.jpg", scheme, currentX];
                NSLog(@"%@", imageName);
            } else if (currentX < 100) {
                imageName = [NSString stringWithFormat:@"%@0%i.jpg", scheme, currentX];
                NSLog(@"%@", imageName);
            } else {
                imageName = [NSString stringWithFormat:@"%@%i.jpg", scheme, currentX];
                NSLog(@"%@", imageName);
            }

            //NSLog(@"%@", myRotationView.image);
            [self.myRotationView setImage:[[UIImage imageNamed:imageName]autorelease]];
            //NSLog(@"%@", myRotationView.image);
        }
        case UIGestureRecognizerStateBegan: {
            [gesture setTranslation:CGPointZero inView:gesture.view];

            NSLog(@"Began");

            break;
        }
        case UIGestureRecognizerStateEnded: {
            //CGPoint velocity = [gesture velocityInView:self.view];
            //The user lifted their fingers. Optionally use the velocity to contain rotating the globe automatically

            NSLog(@"Ended");

            break;
        }
        default: {
            //Something else happened. Do any cleanup you need to.
            NSLog(@"Something else happened.");
        }
    }
}

/*
// Only override drawRect: if you perform custom drawing.
// An empty implementation adversely affects performance during animation.
- (void)drawRect:(CGRect)rect {
    // Drawing code.
}
*/

- (void)dealloc {
    [super dealloc];


    NSLog(@"Rotation Controller - DeAlloc");
    [myRotationView release];
    [scheme release];
    [imageName release];
}

@end

The Back Trace:

2011-04-21 14:38:39.442 MCIT[52259:207] Test - DidBecomeActive
Program received signal:  “EXC_BAD_ACCESS”.
(gdb) backtrace
#0  0x01326a78 in objc_msgSend ()
#1  0x0633d540 in ?? ()
#2  0x000138b2 in -[RotationController applicationDidBecomeActive] (self=0x6607dc0, _cmd=0x17540) at /Users/jacob/Documents/iOS Dev/MCIT/Classes/RotationController.m:83
#3  0x00002a1c in -[MCITAppDelegate applicationDidBecomeActive:] (self=0x6603f30, _cmd=0x6e25a7, application=0x6300700) at /Users/jacob/Documents/iOS Dev/MCIT/Classes/MCITAppDelegate.m:100
#4  0x002d2542 in -[UIApplication _setActivated:] ()
#5  0x002dfe18 in -[UIApplication _handleApplicationResumeEvent:] ()
#6  0x002df7d4 in -[UIApplication handleEvent:withNewEvent:] ()
#7  0x002d7202 in -[UIApplication sendEvent:] ()
#8  0x002dc732 in _UIApplicationHandleEvent ()
#9  0x01afaa36 in PurpleEventCallback ()
#10 0x01afaabd in PurpleEventSignalCallback ()
#11 0x011a601f in __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ ()
#12 0x0110428b in __CFRunLoopDoSources0 ()
#13 0x01103786 in __CFRunLoopRun ()
#14 0x01103240 in CFRunLoopRunSpecific ()
#15 0x01103161 in CFRunLoopRunInMode ()
#16 0x01af9268 in GSEventRunModal ()
#17 0x01af932d in GSEventRun ()
#18 0x002e042e in UIApplicationMain ()
#19 0x00001f0e in main (argc=1, argv=0xbffff070) at /Users/jacob/Documents/iOS Dev/MCIT/main.m:14

it’s failing where I thought on my testing code… when the image is set.

- (void)applicationDidBecomeActive
{
    NSLog(@"Test - DidBecomeActive");

    [self.myRotationView setImage:[UIImage imageNamed:@"Trailer1Rotation_000.jpg"]];
}

Answer 1

I find the easiest way to debug these problems is to turn on NSZombieEnabled for your executable.

Expand the ‘Executable’ item for your project in Xcode, double click on it. Now click the plus (‘+’) icon at the bottom left and add an NSZombieEnabled variable with value YES.

You should only use this setting during development, otherwise memory won’t ever get properly freed by your app. You don’t want to try and deliver your app with this setting turned on.

I check this by adding some test code to my UIApplicationDelegate class:

- (void)applicationDidFinishLaunching:(UIApplication *)application
{
  if (getenv("NSZombieEnabled"))
  {
    NSLog(@"WARNING! NSZombieEnabled enabled!");
  }

  if (getenv("NSAutoreleaseFreedObjectCheckEnabled"))
  {
    NSLog(@"WARNING! NSAutoreleaseFreedObjectCheckEnabled enabled!");
  }