随机动画效果
ViewController.m
1 #import "ViewController.h" 2 #define MAX_SIZE 25//雪花大小 3 #define MAX_TIME 20//飘落时间 4 #define MIN_TIME 5 5 6 @implementation ViewController 7 8 - (void)viewDidLoad 9 { 10 [super viewDidLoad]; 11 //背景颜色 12 [self.view setBackgroundColor:[UIColor colorWithRed:0.45 green:0.45 blue:1 alpha:1]]; 13 14 /*每隔0.05秒执行一次onTimer函数*/ 15 [NSTimer scheduledTimerWithTimeInterval:0.05 target:self selector:@selector(onTimer) userInfo:nil repeats:YES]; 16 } 17 18 #pragma mark - viewDidLoad NSTimer onTimer 19 -(void)onTimer 20 { 21 UIImage *snowImage = [UIImage imageNamed:@"3.png"]; 22 UIImageView *view = [[UIImageView alloc]initWithImage:snowImage]; 23 [snowImage release]; 24 25 /*随机：开始位置、结束位置、大小、速度、透明度*/ 26 int startX = random() % 320; 27 int endX = random() % 320; 28 int width = random() % MAX_SIZE; 29 int time = (random() % (MAX_TIME - MIN_TIME)) + MIN_TIME; 30 float alpha = random() % 1000 / (float)1200; 31 32 //开始位置 从屏幕上沿出现 33 view.frame = CGRectMake(startX, -1*MAX_SIZE, width, width); 34 view.alpha = alpha;//透明度 35 36 [self.view addSubview:view]; 37 38 [UIView beginAnimations:nil context:view]; 39 //速度 40 [UIView setAnimationDuration:time]; 41 42 //结束位置 43 view.frame = CGRectMake(endX, 480, width, width); 44 //解决内存溢出 45 [UIView setAnimationDidStopSelector:@selector(onAnimationComplete:finished:context:)]; 46 [UIView setAnimationDelegate:self]; 47 48 [UIView commitAnimations]; 49 } 50 51 #pragma mark - onTimer UIView onAnimationComplete:finished:context: 52 53 - (void)onAnimationComplete:(NSString*)animationID finished:(NSNumber*)finished context:(void*)context 54 { 55 UIImageView *snowView = context; 56 if (snowView == nil) { 57 return; 58 } 59 [snowView removeFromSuperview]; 60 // [snowView release];//若两个都执行会崩 61 } 62 63 @end
