Question

我设置了一个CAEmitterLayer，它运行正常：

-(void)awakeFromNib
{
    //set ref to the layer
    emitter = (CAEmitterLayer*)self.layer;
    emitter.emitterPosition = CGPointMake(160, 270);

    CAEmitterCell* grassLeft = [self getEmitter];
    CAEmitterCell* grassRight = [self getEmitter];
    grassLeft.emissionLongitude = M_PI*1.20;
    grassRight.emissionLongitude = M_PI*1.80;

    //add the cell to the layer and we're done
    emitter.emitterCells = [NSArray arrayWithObjects:grassLeft,grassRight,nil];


}

但我添加了一行代码：

-(void)awakeFromNib {
    //set ref to the layer
    emitter = (CAEmitterLayer*)self.layer;
    emitter.emitterPosition = CGPointMake(160, 270);
    emitter.backgroundColor = [[UIColor redColor] CGColor];

    CAEmitterCell* grassLeft = [self getEmitter];
    CAEmitterCell* grassRight = [self getEmitter];
    grassLeft.emissionLongitude = M_PI*1.20;
    grassRight.emissionLongitude = M_PI*1.80;

    //add the cell to the layer and we're done
    emitter.emitterCells = [NSArray arrayWithObjects:grassLeft,grassRight,nil];


}

突然之间，我得到Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[CALayer setEmitterPosition:]: unrecognized selector sent to instance 0x7546390'。调试窗口说该对象是CAEmitterLayer，而不仅仅是CALayer。当我删除那行代码时，问题仍然存在。

Answer 1

我假设此代码在自定义UIView中，如果是这样，请确保已覆盖：

+ (Class)layerClass

所以它应该是：

+ (Class)layerClass
{
    return [CAEmitterLayer class];
}

这将确保你所在的UIView里面有

emitter = (CAEmitterLayer*)self.layer;

它返回一个CAEmitterLayer，而不是它默认执行的普通CALayer。

我猜这是问题所在，因为错误表明你试图在普通的CALayer上调用一个只存在于CAEmitterLayer上的方法。

方法发送到CAEmitterLayer但转到CALayer

1 个答案: