Question

My app moves 10 UIImageViews randomly around the screen, and once an UIImageView hits the corner, it changes its image. The problem is: after switching between apps and going back to mine, the app crashes.

The console gives me this message:

"App" exited abnormally with signal 10: Bus error

The crash log states this:

Exception Type:  EXC_BAD_ACCESS (SIGBUS)

Exception Codes: KERN_PROTECTION_FAILURE at 0x0000000000000011

Crashed Thread:  0  Dispatch queue: com.apple.main-thread

I think the problem is due to the fact that I’m using UIImage imageNamed, here is the code:

In ViewController.h:

UIImage *red;
UIImage *green;
UIImage *blue;

UIImageView *ballOne;
UIImageView *ballTwo;
UIImageView *ballThree;
UIImageView *ballFour;
// And declare UIImageView for other balls
int clr

In ViewController.m:

- (void)viewDidLoad {
  ...
  red = [UIImage imageNamed: @"redTexture.png"];
  green = [UIImage imageNamed: @"greenTexture.png"];
  blue = [UIImage imageNamed: @"blueTexture.png"];
  ...
}
- (void)moveAll:(NSTimer *)theTimer{
  ...
  // If UIImageView touches a corner, Do this:
  clr = arc4random()%3 + 1;
  switch (clr) {
    case 1:
     [ballOne setImage:red];
     break;
    case 2:
     [ballOne setImage:green];
     break;
    case 3:
     [ballOne setImage:blue];
     break;
    default:
     break;
   }
   // And do this for the rest of 9 "balls" 
}

Why does my App crash, and how do I solve it?

Answer 1

[UIImage imageNamed:] returns an autoreleased instance of a UIImage. That means that the memory will be released as soon as the event loop ends.

Yo need to retain those instance either by calling.

[[UIImage imageNamed:@"blabl.png"] retain]

or (preferred method) by setting up your blue, red, green members as property with

@property(nonatomic, retain) UIImage* red;

and your code will be like :

- (void)viewDidLoad {
  ...
  self.red = [UIImage imageNamed: @"redTexture.png"];
  self.green = [UIImage imageNamed: @"greenTexture.png"];
  self.blue = [UIImage imageNamed: @"blueTexture.png"];
  ...
}

Of course do not forget to release them when your done otherwize you will have the opposite of what you have now : memory leaks.

to release red, call

[red release]

inthe dealloc method.