iOS 动画 —— 礼花效果实例详细

- (void)viewDidLoad {
 [super viewDidLoad];
 [self makeFireworksDisplay];
}

- (void)makeFireworksDisplay {
 // 粒子发射系统 的初始化
 CAEmitterLayer *fireworksEmitter = [CAEmitterLayer layer];
 CGRect viewBounds = self.view.layer.bounds;
 // 发射源的位置
 fireworksEmitter.emitterPosition = CGPointMake(viewBounds.size.width/2.0, viewBounds.size.height);
 // 发射源尺寸大小
 fireworksEmitter.emitterSize = CGSizeMake(viewBounds.size.width/2.0, 0.0);
 // 发射模式
 fireworksEmitter.emitterMode = kCAEmitterLayerOutline;
 // 发射源的形状
 fireworksEmitter.emitterShape = kCAEmitterLayerLine;
 // 发射源的渲染模式
 fireworksEmitter.renderMode = kCAEmitterLayerAdditive;
 // 发射源初始化随机数产生的种子
 fireworksEmitter.seed = (arc4random()%100)+1;

 /**
  * 添加发射点
  一个圆（发射点）从底下发射到上面的一个过程
  */
 CAEmitterCell* rocket = [CAEmitterCell emitterCell];
 rocket.birthRate = 1.0; //是每秒某个点产生的effectCell数量
 rocket.emissionRange = 0.25 * M_PI; // 周围发射角度
 rocket.velocity = 400; // 速度
 rocket.velocityRange = 100; // 速度范围
 rocket.yAcceleration = 75; // 粒子y方向的加速度分量
 rocket.lifetime = 1.02; // effectCell的生命周期，既在屏幕上的显示时间要多长。

 // 下面是对 rocket 中的内容，颜色，大小的设置
 rocket.contents = (id) [[UIImage imageNamed:@"circle"] CGImage];
 rocket.scale = 0.2;
 rocket.color = [[UIColor redColor] CGColor];
 rocket.greenRange = 1.0;
 rocket.redRange = 1.0;
 rocket.blueRange = 1.0;
 rocket.spinRange = M_PI; // 子旋转角度范围

 /**
  * 添加爆炸的效果，突然之间变大一下的感觉
  */
 CAEmitterCell* burst = [CAEmitterCell emitterCell];
 burst.birthRate = 1.0;
 burst.velocity = 0;
 burst.scale = 2.5;
 burst.redSpeed =-1.5;
 burst.blueSpeed =+1.5;
 burst.greenSpeed =+1.0;
 burst.lifetime = 0.35;

 /**
  * 添加星星扩散的粒子
  */
 CAEmitterCell* spark = [CAEmitterCell emitterCell];
 spark.birthRate = 400;
 spark.velocity = 125;
 spark.emissionRange = 2* M_PI;
 spark.yAcceleration = 75; //粒子y方向的加速度分量
 spark.lifetime = 3;

 spark.contents = (id) [[UIImage imageNamed:@"star"] CGImage];
 spark.scaleSpeed =-0.2;
 spark.greenSpeed =-0.1;
 spark.redSpeed = 0.4;
 spark.blueSpeed =-0.1;
 spark.alphaSpeed =-0.25; // 例子透明度的改变速度
 spark.spin = 2* M_PI; // 子旋转角度
 spark.spinRange = 2* M_PI;

 // 将 CAEmitterLayer 和 CAEmitterCell 结合起来
 fireworksEmitter.emitterCells = [NSArray arrayWithObject:rocket];
 //在圈圈粒子的基础上添加爆炸粒子
 rocket.emitterCells = [NSArray arrayWithObject:burst];
 //在爆炸粒子的基础上添加星星粒子
 burst.emitterCells = [NSArray arrayWithObject:spark];
 // 添加到图层上
 [self.view.layer addSublayer:fireworksEmitter];

}