對UIView隨機位置和開始時間的閃爍效果

Question

如何在應用程序上創建一個像閃閃效果的魔術？

Answer 1

//Header file 

#import "QuartzCore/QuartzCore.h" 

@interface SparklesViewController : UIViewController 
{ 
CAEmitterLayer *emitter; 
} 

//Implementation file 

    - (void)viewDidLoad 
    { 
     [NSTimer scheduledTimerWithTimeInterval:3 target:self selector:@selector(destroyEmitter) userInfo:nil repeats:YES]; 
     [self sparklesIt]; 
     [super viewDidLoad]; 
     // Do any additional setup after loading the view, typically from a nib. 
    } 

    -(void)sparklesIt 
    { 
    int delay; 

    UIImage *image; 

    int imgSel=[self numberWithMin:0 :6]; 
    switch (imgSel) { 
     case 0: 
     image=[UIImage imageNamed:@"green.png"]; 
     break; 
     case 1: 
     image=[UIImage imageNamed:@"silver.png"]; 
     break; 
     case 2: 
     image=[UIImage imageNamed:@"yellow.png"]; 
     break; 
     case 3: 
     image=[UIImage imageNamed:@"red.png"]; 
     break; 
     case 4: 
     image=[UIImage imageNamed:@"purple.png"]; 
     break; 
     case 5: 
     image=[UIImage imageNamed:@"pink.png"]; 
     break; 
     case 6: 
     image=[UIImage imageNamed:@"blue.png"]; 
     break; 
     default: 
     break; 
    } 

    CGPoint pt=CGPointMake([self numberWithMin:0 :320],[self numberWithMin:0 :460]); 

    float multiplier=0.25f; 

    //create the emitter layer 
    emitter=[CAEmitterLayer layer]; 
    emitter.emitterPosition=pt; 
    emitter.emitterMode=kCAEmitterLayerOutline; 
    emitter.emitterShape=kCAEmitterLayerCircle; 
    emitter.renderMode=kCAEmitterLayerAdditive; 
    emitter.emitterSize=CGSizeMake(100*multiplier, 0); 

    //Flare particles emitted from the rocket as it flys 
    CAEmitterCell *flare = [CAEmitterCell emitterCell]; 
    flare.contents = (__bridge id)([image CGImage]); 
    flare.emissionLongitude = (4 * M_PI)/2; 
    flare.scale = 0.4; 
    flare.velocity = 100; 
    flare.birthRate = 45; 
    flare.lifetime = 1; 
    flare.emissionRange = M_PI/7; 
    flare.alphaSpeed = -0.7; 
    flare.scaleSpeed = -0.1; 
    flare.scaleRange = 0.1; 
    flare.beginTime = 0.01; 
    flare.duration = 0.7; 

    emitter.emitterCells=[NSArray arrayWithObject:flare]; 
    [self.view.layer addSublayer:emitter]; 

    delay=[self numberWithMin:5 :10]; 
    [self performSelector:@selector(sparklesIt) withObject:nil afterDelay:delay]; 
    } 

    -(void)destroyEmitter 
    { 
    NSLog(@"destroy emitter called "); 
    if (emitter!=nil) { 
     [emitter removeFromSuperlayer]; 
     emitter=nil; 
    } 
    } 

    -(int)numberWithMin:(int)min:(int)max 
    { 
    return rand() % (max - min) + min; 
    } 

//綠色，如它的名字規定紫色，紅色等都是用不同的顏色恆星的圖像，其大小是16×16