iOS实现爆炸的效果

    CAEmitterLayer *emitter = [CAEmitterLayer layer];

    emitter.frame = self.view.bounds;     [self.view.layer addSublayer:emitter];     emitter.renderMode = kCAEmitterLayerAdditive;     emitter.emitterPosition = CGPointMake(emitter.frame.size.width/2, emitter.frame.size.height/2);     CAEmitterCell *cell = [[CAEmitterCell alloc] init];     cell.contents = (__bridge id)[UIImage imageNamed:@"yuandan1"].CGImage;     cell.birthRate = 150;     cell.lifetime = 5;     cell.alphaSpeed = -0.4;     cell.velocity = 50;     cell.velocityRange = 50;     cell.emissionRange = M_PI *2.0;

    emitter.emitterCells = @[cell];