iOS-如何按顺序显示大量图像

Question

I am working on an app that needs to flip through 300 or so images in sequence, with a 2 second delay between images.

These images are barcodes that are generated on the fly during the display. They are not stored images.

The display is in a navigation controller and I would like the user to be able to click the 'back' button without the app crashing from a selector being sent to an instance that no longer exists.

I know that it is possible to animate a UIImageView, but I don't want to create an large array of images because of memory issues.

I'd like to do this in a loop where I generate the barcode, display the image, delay 2 seconds, and then repeat with the next image.

The following code works, but crashes if you click the 'back' button, with a 'message sent to deallocated instance' error.

   NSSet *dataSet = [self fetchDataSet];

    for (MyBarCode *data in dataSet) {

        // display barcode in UIImageView
        [self updateBarCodeImage:data ];

        [[NSRunLoop currentRunLoop] runUntilDate:[NSDate dateWithTimeIntervalSinceNow: 2.0]];
    }

There doesn't seem to be a way to cancel this timer, or I could do that in viewWillDisapear.

What's the right way to do this?

Please don't just point me to the animationImages examples. I've already seen all of them and -- again -- I don't want to have to hold all these images in memory during the animation. If there's a way to generate the images on the fly during animation, now that would be interesting.

Answer 1

I think something like this should work:

__weak ViewController *bSelf = self;
NSSet *dataSet = [self fetchDataSet];
dispatch_queue_t myQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0ul);
dispatch_async(myQueue, ^{
    __strong ViewController *sSelf = bSelf;

    for (BoardingPass *data in dataSet) {
    {
        dispatch_after(dispatch_time(DISPATCH_TIME_NOW, 2 * NSEC_PER_SEC), dispatch_get_main_queue(), ^{
        [sSelf updateBarCodeImage:data]
        });
    }

});

Answer 2

UPDATED:

Well I am not sure what exactly you are looking for. If you are talking about a simple animation than yes, Cocos 2D would be overkill. In that case I suggest doing this tutorial which gave me a lot of ideas on a project I was working on some time back:

http://www.raywenderlich.com/2454/how-to-use-uiview-animation-tutorial