CAEmitterCell不考虑持续时间值

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的一部分已经有大约两年了，但关于这方面的信息似乎很少！

Answer 1

你可以用一个计时器和一个停止发射器产生新粒子的方法来做到这一点。

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];

然后创建一个方法:stopEmitter…

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