CAEmitterCell不尊重持续时间值

Question

我有一个发射器，我想在2秒后结束，但我不能让它停止运行!

我的代码如下:

// Emitter Layer
    //
    emitter = [CAEmitterLayer layer];
    emitter.emitterSize = CGSizeMake(20, 20);
    emitter.renderMode = @"additive";
    emitter.emitterMode = @"points";
    emitter.emitterShape = @"rectangle";
    emitter.emitterPosition = CGPointMake(310, 230);
    //emitter.duration = 2; // setting duration on the emitterLayer prevents anything from firing it seems
// Emitter Cells
    //
    // 'New Emitter' cell configuration
    newEmitter = [CAEmitterCell emitterCell];
    newEmitter.scaleSpeed = 7;
    newEmitter.lifetime = 2.481715;
    //newEmitter.duration = 2; // I would expect this to stop the emitter after 2 seconds, but it doesn't!
    newEmitter.velocity = 332.3636968085106;
    newEmitter.contents = newemitterImg;
    newEmitter.name = @"New Emitter";
newEmitter.scaleRange = 4.178236607142859;
    newEmitter.lifetimeRange = 1.6;
    newEmitter.greenRange = -2.775558e-17;
    newEmitter.birthRate = 40;
    newEmitter.emissionRange = -6.283185306666667;
    newEmitter.scale = 0;
    // Emitter Cell Chains
    //
    emitter.emitterCells = [NSArray arrayWithObjects:newEmitter, nil];

尽管作为iOS的一部分已经有2年了，但关于这一点的信息似乎很少!

Answer 1

你可以用一个计时器，和一个方法来停止发射器产生新的粒子…

在现有代码的末尾添加:

    [newEmitter setName:@"newEmitter"];
    [NSTimer scheduledTimerWithTimeInterval:2.0
                                     target:self
                                   selector:@selector(stopEmitter:)
                                   userInfo:nil
                                    repeats:NO];

然后创建一个stopEmitter: method…

    - (void) stopEmitter:(NSTimer*)timer
    {
        [emitter setValue:@0
               forKeyPath:@"emitterCells.newEmitter.birthRate"];
    }