Can anyone point me to some strategies for debugging memory leaks in monotouch?

I am almost finished with my first monotouch app, almost that is, but for some big problems with memory leaks. Even though I override the viewDidUnload on every view controller so that for every UI element that I create I first remove it from its superview, then call Dispose and then set it to null, the problem persists. Using Instruments is no help, it doesn't detect the memory leaks and the memory allocations doesn't point me to anything that I can track.

My app uses mainly the MPMoviePlayer to play video streams and also displays an image gallery from images loaded through http. Both operation are causing problems.

Any ideas wou开发者_如何学JAVAld be very much appreciated, thanks.

The Master is right of course. Gracias Miguel. I wanted though to give a more thorough explanation of what I did, with the hope that it may help future Xamarin colleges.

1) The MPMoviePlayer stores a video buffer which is kind of sticky. What I have done is have a unique instance running on the AppDelegate an reuse this across the views that show a video. So instead of initializing the MPMoviePlayerController with an url you use the constructor with no arguments, and then set the ContentUrl property and call Play().

2) Do not rely on ViewDidUnload being called to clean up you objects, because it is not called consistently. For example I use a lot of modal view controllers and this method never got called. Memory just kept accumulating until the app crashed. Better call you clean up code directly.

3) Images were the biggest memory hug I had. Even Images inside UIImageViews that were just used as background would never get disposed. I had to specifically call the following code on each image before I could clear up the memory:

myImageView.RemoveFromSuperview();
myImageView.Image.Dispose();
myImageView.Image = null;
myImageView.Dispose();
myImageView = null;

4) Beware of the UIWebView, it can hug a lot of memory, specially if there is some kind of AJAX interaction running on the page that you are loading. Calling the following code help a little but didn't solve all the problems. Some memory leaks remain that I wasn't able to get rid off:

NSString keyStr = new NSString("WebKitCacheModelPreferenceKey");
NSUserDefaults.StandardUserDefaults.SetValueForKey(NSObject.FromObject(val), keyStr);

5) If you can, avoid using Interface Builder. On several occasions I was never able to release UI elements created on the xib files. Positioning everything by hand can be a pain but if you are using a memory intensive application creating all your view controllers in code may be the way to go.

6) Using anonymous methods as event handlers is nice and my help code readability, but on some occasions not being able to manually detach an event handler became a problem. References to unwanted object remain in memory.

7) In my UITableViewSource I was able to have a more efficient memory handling by creating the UIImages that I use to style the cells independently and then just reusing them on my GetViewForHeader and GetCell methods.

One last thing; even though instruments is not really compatible with the way monotouch is doing things using the "Memory Monitor" was a valuable tool, if you are having problem it can indeed help.

These strategies solved most of my problems. Some may be pretty obvious in hindsight but I thought it wont hurt to pass them along.

Happy Coding and long live c# on the iPhone

The UI elements are not likely the responsible ones, those barely use any memory. And calling Dispose()/nulling helps, but only a tiny bit.

The more likely source of the problem are objects like the MPMoviePlayer, the image downloading and the image rendering. You might be keeping references to those objects which prevent the GC from getting rid of them.