Discursive UIAlertView animation while continuous animation? - iphone

Question

I'm trying to write a little app, where on the main screen, I animate a flying "bubble". This animation has to be continuous. (I reuse the bubbles, which fly off the screen) I heard that animations have to run on the main thread, as does every operation which changes the UI. Is this true? When I try to show a UIAlertView on this screen, it's animation becomes very discursive because of the continuous bubble animation. (this is a custom alertview with an indicator) The device is an iPhone 4, so I don't think it should be a problem to show a normal UIAlertView.
And I would like to ask if I use the correct method for the bubble animation. So first of all, I use an NSTimer, which invokes the startAnimation method in every 0.01 seconds (I start it in the controller's viewDidAppear: method). In the startAnimation method, at first I generate bubbles with random x and y coordinates (to see bubbles on the screen right after the viewdidappear), and I generate bubbles on the bottom with random x and y = 460 coordinates. In the startAnimation method, I run a counter (called frames), and when the value of this counter equals 35, I call the bubble generate method again.
The problem:
I store the generated bubbles in an array, and the 'gone' bubbles (which are off the screen) in another array. First I try to reuse the bubbles in the gonebubbles array, then if the array is run out, I generate new bubbles. While this operation is processed, the continuous animation stops, then continues. The break is about one second, but this is very disturbing.
Can anyone help in this problem? Thanks in advice, madik
- (void)viewDidAppear {
.
timer = [NSTimer scheduledTimerWithTimeInterval:0.01 target:self selector:#selector(startAnimation) userInfo:nil repeats:YES];
.
}
- (void)startAnimation {
self.current = [NSDate timeIntervalSinceReferenceDate];
double diff = (self.start - self.current);
if ( diff < 0 ) {
diff = (-1) * diff;
}
self.start = self.current;
frames++;
if ( shouldMoveBubbles ) {
[mug moveBubbles:diff];
}
if ( frames == 35 ) {
DebugLog(#"################################################################");
DebugLog(#"####################### FRAME = 35 ###########################");
DebugLog(#"################################################################");
[mug createNewBubbleOnTheBottomOfView:self.view];
frames = 0;
}
}
In the Mug class:
- (void)moveBubbles:(double)millisElapsed {
for (Bubble *bubble in bubbles) {
int bubbleSpeed = bubble.speed;
float deltaX = (float)(bubbleSpeed * -degrees_sinus * millisElapsed * 100);
float deltaY = (float)(bubbleSpeed * -degrees_cosinus * millisElapsed);
DebugLog(#"movebubbles x: %f, y:%f, speed: %d, sin:%f, cos:%f", deltaX, deltaY, bubbleSpeed, degrees_sinus, degrees_cosinus);
[bubble moveBubbleX:deltaX Y:deltaY];
}
}
And in the Bubble class:
- (void)moveBubbleX:(float)deltaX Y:(float)deltaY {
self.bubbleImage.center = CGPointMake(self.bubbleImage.center.x + deltaX, self.bubbleImage.center.y + deltaY);
}

Answer 1

This sounds like a memory problem. Slow UIAlertView animation is a sure sign of this. It sounds like the way you are generating bubbles is causing the problem. You mentioned the you keep two arrays of bubbles. You never say if you limit the number of bubbles that can be in either array at once. You also don't mention when you clean up these bubbles. It sounds like a memory "black hole". I'd recommend setting a maximum number of bubbles that you can show on screen at once.
Also, you mention a custom alert view. If you're modifying the UIAlertView, you're going to run into problems since that's not officially supported. Additionally, I've seen UIAlertView animation become slow when memory is tight. If you solve the memory issues with your bubbles, you'll probably solve this one too.
Finally, a word of advice. Making an animated game in UIKit is probably not a good idea. NSTimers are not as accurate as many people would like to think. UIImages are relatively expensive to load. Touching moving buttons is known to be unreliable at worst, hackish at best. I suggest looking into a game framework, such as Cocos2d-iphone.
Good luck!