cabasicanimation animationdidstop flag = false

[奔雷手]

        CABasicAnimation *pathAnimation = [CABasicAnimation animationWithKeyPath:@"strokeEnd"];
        pathAnimation.duration = 4;
        pathAnimation.fromValue = @(0.0);
        pathAnimation.toValue = @(1.0);
        pathAnimation.removedOnCompletion = YES;
        pathAnimation.delegate = self;

#pragma mark -- CAAnimationDelegate
- (void)animationDidStop:(CAAnimation *)anim finished:(BOOL)flag
{
    if (flag) {
        
    }
}

flag一直为false，这是什么造成的