CAEmitterLayer 在触摸事件中随机发射不需要的粒子

Question

我正在尝试设置CAEmitterLayer 来制作五彩纸屑效果，我遇到了两个问题：

1. 每当我将单元格上的 birthRate 设置为非零值以启动动画时，我都会在屏幕上随机放置一系列单元格，这些单元格可以正常动画，然后发射器在此之后继续正常发射。李>
2. 每当emitterCells 在屏幕上绘制东西时，只要我触摸屏幕，发射器就会在（看似）随机位置绘制emitterCells，这些位置存在（看似）随机的时间量。发射器中的任何内容都与任何触摸事件无关（即我不是故意在触摸事件上绘制任何东西），但该层位于具有多个嵌入式视图的视图中。我触摸的次数越多，显示的单元格就越多。

这是我设置发射器的代码，然后启动和停止它（一旦我调用了停止函数，然后点击屏幕停止创建新的随机元素）：

- (void)setupConfetti
{
    self.confettiLayer = [CAEmitterLayer layer];
    [self.view.layer addSublayer:self.confettiLayer];
    [self.view.layer setNeedsDisplay];

    self.confettiLayer.emitterPosition = CGPointMake(1024.0/2,-50.0);
    self.confettiLayer.emitterSize = CGSizeMake(1000.0, 10.0);
    self.confettiLayer.emitterShape = kCAEmitterLayerLine; 
    self.confettiLayer.renderMode =kCAEmitterLayerUnordered;

    CAEmitterCell *confetti = [CAEmitterCell emitterCell];

    confetti1.contents =  (id)[[UIImage imageNamed:@"confetti.png"] CGImage];

    confetti.emissionLongitude = M_PI;
    confetti.emissionLatitude = 0;
    confetti.lifetime = 5;
    confetti.birthRate = 0.0;
    confetti.velocity = 125;
    confetti.velocityRange = 50;
    confetti.yAcceleration = 50;
    confetti.spin = 0.0;
    confetti.spinRange = 10;
    confetti.name = @"confetti1";

    self.confettiLayer.emitterCells = [NSArray arrayWithObjects:confetti, nil];
}

开始五彩纸屑：

- (void)startConfettiAnimation
{
    [self.confettiLayer setValue:[NSNumber numberWithInt:10.0] forKeyPath:@"emitterCells.confetti.birthRate"];
}

然后停止它：

- (void)stopConfettiAnimation
{
    [self.confettiLayer setValue:[NSNumber numberWithInt:0.0] forKeyPath:@"emitterCells.confetti.birthRate"];
}

再一次，一旦开始，经过最初的随机元素，它就可以正常工作：一切正常动画，当birthRate稍后设置为零时，它会优雅地结束。它似乎只是响应触摸事件，我不知道为什么。我尝试将emitterLayer 添加到不同的视图，禁用该视图上的用户交互，然后将其添加为主视图的子视图，但这似乎不起作用。

任何帮助/见解将不胜感激！

谢谢， 山姆

Answer 1

我知道这是一篇旧帖子，但我也遇到了这个问题。 Jackslash 在这篇文章中很好地回答了这个问题： iOS 7 CAEmitterLayer spawning particles inappropriately

您需要使用 CACurrentMediaTime() 将发射器层上的 beginTime 设置为从当前时间开始。看来我们遇到的问题是因为发射器已经在过去启动了。

emitter.beginTime = CACurrentMediaTime();

Answer 2

您是否没有像 Artur Ozieranski 发布的 Wenderlich 示例中那样检查粒子是否正在发射？只要支票到位，我就不会看到翻倍。

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
    [fireView setEmitterPositionFromTouch: [touches anyObject]];
    [fireView setIsEmitting:YES];
}

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
    [fireView setIsEmitting:NO];
}

- (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event {
    [fireView setIsEmitting:NO];
}
-(void)setIsEmitting:(BOOL)isEmitting
{
    //turn on/off the emitting of particles
    [fireEmitter setValue:[NSNumber numberWithInt:isEmitting?200:0] forKeyPath:@"emitterCells.fire.birthRate"];
}

Answer 3

.h 文件

 #import <UIKit/UIKit.h>

    @interface DWFParticleView : UIView

    -(void)setEmitterPositionFromTouch: (CGPoint*)t;
    -(void)setIsEmitting:(BOOL)isEmitting;

    @end

.m 文件

  #import "DWFParticleView.h"
    #import <QuartzCore/QuartzCore.h>

    @implementation DWFParticleView
    {
        CAEmitterLayer* fireEmitter; //1
    }

    -(void)awakeFromNib
    {
        //set ref to the layer
        fireEmitter = (CAEmitterLayer*)self.layer; //2
        //configure the emitter layer
        fireEmitter.emitterPosition = CGPointMake(50, 50);
        fireEmitter.emitterSize = CGSizeMake(10, 10);

        CAEmitterCell* fire = [CAEmitterCell emitterCell];
        fire.birthRate = 0;
        fire.lifetime = 1.5;
        fire.lifetimeRange = 0.3;
        fire.color = [[UIColor colorWithRed:255 green:255 blue:255 alpha:0.1] CGColor];
        fire.contents = (id)[[UIImage imageNamed:@"Particles_fire.png"] CGImage];
        [fire setName:@"fire"];

        fire.velocity =5;
        fire.velocityRange = 20;
        fire.emissionRange = M_PI_2;

        fire.scaleSpeed = 0.1;
        fire.spin = 0.5;

        fireEmitter.renderMode = kCAEmitterLayerAdditive;

        //add the cell to the layer and we're done
        fireEmitter.emitterCells = [NSArray arrayWithObject:fire];

    }

    + (Class) layerClass //3
    {
        //configure the UIView to have emitter layer
        return [CAEmitterLayer class];
    }

    -(void)setEmitterPositionFromTouch: (CGPoint*)t
    {
        //change the emitter's position
        fireEmitter.emitterPosition = (*t);
    }

    -(void)setIsEmitting:(BOOL)isEmitting
    {
        //turn on/off the emitting of particles
        [fireEmitter setValue:[NSNumber numberWithInt:isEmitting?100:0] forKeyPath:@"emitterCells.fire.birthRate"];
    }


    @end

我使用此代码创建自定义视图并在其上发射粒子 触摸

这里是触摸发射粒子的调用语句

-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    CGPoint p =  [[touches anyObject] locationInView:self.view];
     [fireView setEmitterPositionFromTouch: &p];
     [fireView setIsEmitting:YES];

}

也许它对你有用。