ios7 中的 UIKit 粒子系统。粒子数增加

Posted 2023-03-16

【中文标题】ios7 中的 UIKit 粒子系统。粒子数增加

【英文标题】：UIKit Particle Systems in ios7. Number of particles increased

【发布时间】：2013-09-12 13:36:27

【问题描述】：

ios7 上的粒子系统似乎与 ios6 和 ios5 上的不同。粒子数增加。 应用程序中的所有粒子效果都会出现同样的问题。 唯一可行的解​​决方案是检查是否是 ios7 并降低粒子出生率。有没有更好的解决方案？

粒子发射器视图代码。

- (id)initWithFrame:(CGRect)frame

    self = [super initWithFrame:frame];
    if (self) 
        //initialize the emitter
        _emitter = (CAEmitterLayer*)self.layer;
        _emitter.emitterPosition = CGPointMake(self.bounds.size.width /2, self.bounds.size.height/2 );
        _emitter.emitterSize = self.bounds.size;
        _emitter.emitterMode = kCAEmitterLayerAdditive;
        _emitter.emitterShape = kCAEmitterLayerRectangle;
    
    return self;


- (void)didMoveToSuperview

    //Check if parent is initialized
    [super didMoveToSuperview];
    if (self.superview==nil) return;

    //Load png
    UIImage* texture = self.explosionImage; //[UIImage imageNamed:@"particle.png"];
    NSAssert(texture, @"particle.png not found");

    //Create a new emitter cell
    CAEmitterCell* emitterCell = [CAEmitterCell emitterCell];

    //Set the cell’s contents property to the texture you loaded
    emitterCell.contents = (__bridge id)[texture CGImage];

    //Name the cell “cell”
    emitterCell.name = @"cell";

    //Parameters
    emitterCell.birthRate = self.birthRate;// 40;//1000
    emitterCell.lifetime = 2.8;
    emitterCell.lifetimeRange = 0.7;

    //Set the cell’s color to randomly vary its components
    if (!self.explosionColor) 
        emitterCell.blueRange = 0.33;
        emitterCell.blueSpeed = -0.33;
        emitterCell.redRange = 0.33;
        emitterCell.redSpeed = -0.33;
        emitterCell.greenRange = 0.33;
        emitterCell.greenSpeed = -0.33;
    

    //Explosion color
    if (self.explosionColor) emitterCell.color = [self.explosionColor CGColor];

    //velocity
    emitterCell.velocity = IS_IPAD?40:20;//160
    emitterCell.velocityRange = RANDOMF(10, 20);//15

    //Alpha
    emitterCell.alphaSpeed = -0.73;
    emitterCell.alphaRange = 0.9;

    //Scale
    emitterCell.scale = IS_IPAD?0.6:0.30;//0.5
    emitterCell.scaleRange = 0.6;//0.5
    emitterCell.scaleSpeed = 0;

    //Range
    emitterCell.emissionRange = M_PI*2;//2

    //Add the cell to the emitter layer
    _emitter.emitterCells = @[emitterCell];

    [self performSelector:@selector(disableEmitterCell) withObject:nil afterDelay:self.cellIsEmitting];
    [self performSelector:@selector(removeFromSuperview) withObject:nil afterDelay:self.emittingInView];

【参考方案1】：

在 iOS7 上运行时，看起来粒子系统在添加发射器层之前开始动画。 这可能是一个错误，希望将来会得到解决。

目前，要获得与 iOS6 上类似的行为，可以将 CAEmitterLayer 的 beginTime 设置为当前时间：

_emitter.beginTime = CACurrentMediaTime();