无需 opengl 和 cocos2D 创建粒子。降雪应用

Question

好吧，我想在没有 openGL 或 cocs2D 的情况下创建像 (snow ) 这样的粒子，我发现了这个名为 snowfall 的示例代码，在这段代码中有这样的内容：

flakeImage = [UIImage imageNamed:@"flake.png"];

// start a timet that will fire 20 times per second
[NSTimer scheduledTimerWithTimeInterval:(0.5) target:self selector:@selector(onTimer) userInfo:nil repeats:YES];
}



// Timer event is called whenever the timer fires

- (void)onTimer
{


// build a view from our flake image
UIImageView* flakeView = [[UIImageView alloc] initWithImage:flakeImage];

// use the random() function to randomize up our flake attributes
int startX = round(random() % 320);
int endX = round(random() % 320);
double scale = 1 / round(random() % 100) + 1.0;
double speed = 1 / round(random() % 100) + 1.0;

// set the flake start position
flakeView.frame = CGRectMake(startX, -100.0, 5.0 * scale, 5.0 * scale);
flakeView.alpha = 0.25;

// put the flake in our main view
[self.view addSubview:flakeView];

[UIView beginAnimations:nil context:flakeView];
// set up how fast the flake will fall
[UIView setAnimationDuration:5 * speed];

// set the postion where flake will move to
flakeView.frame = CGRectMake(endX, 500.0, 5.0 * scale, 5.0 * scale);

// set a stop callback so we can cleanup the flake when it reaches the
// end of its animation
[UIView setAnimationDidStopSelector:@selector(onAnimationComplete:finished:context:)];
[UIView setAnimationDelegate:self];
[UIView commitAnimations];  }
- (void)onAnimationComplete:(NSString *)animationID finished:(NSNumber *)finished context:(void *)context {

UIImageView *flakeView = context;
[flakeView removeFromSuperview];
// open the debug log and you will see that all flakes have a retain count 
// of 1 at this point so we know the release below will keep our memory 
// usage in check
NSLog([NSString stringWithFormat:@"[flakeView retainCount] = %d", [flakeView retainCount]]);
[flakeView release];


}

我想知道这段代码是否会损害性能或内存（也许是因为它使用计时器）？如果这不是一个好主意，我听说 CAReplicator 可以用于 iphone，但 CAReplicatorDemo 只适用于苹果文档中的 mac :/ 抱歉我的英语我是法国人：/

Answer 1

当然，这会影响性能。但您不会在模拟器中看到它。 UIImageView 太重，无法每秒创建 20 次。您可以尝试使用 CALayer-s 池（和 CAAnimation）。

Answer 2

您可以使用 CAEmitterLayer 来在 iOS 5 上做粒子效果。我以前用过它来处理火焰和烟雾，但它应该适用于雪。

Answer 3

你可以试试我的KHParticleView，它使用cocos2d粒子并在顶部添加cocos2d视图。检查此处的代码：https://github.com/lephukhanhhuy/KHParticleView