失效后CADisplayLink不能停止

Question

我有两个UIButton，第一个按钮将触发CustomeView的- beginAnimation，另一个将触发- endAnimation。当我依次快速按下这两个按钮时，比如begin -> end -> begin -> end -> begin -> end，我发现CADisplayLink无法停止。更重要的是，- rotate的火灾率超过60 fix，变成了60 -> 120 -> 180，就像我的主RunLoop中有多个CADisplaylink一样，那么还有什么可以修复的吗?而且我需要在视图的alpha值降到零之前保持CADisplaylink运行，所以我把[self.displayLink invalidate];放在完成块中，这可能会导致这个问题？

@interface CustomeView : UIView
@end

@implementation CustomeView

- (void)beginAnimation // triggered by a UIButton
{
    [UIView animateWithDuration:0.5 animations:^{ self.alpha = 1.0; }];
    self.displayLink = [CADisplayLink displayLinkWithTarget:self selector:@selector(rotate)];
    [self.displayLink addToRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
}

- (void)endAnimation // triggered by another UIButton
{
    [UIView animateWithDuration:0.5 animations:^{ self.alpha = 0.0; } completion:^(BOOL finished) {
        [self.displayLink invalidate];
    }];
}

- (void)rotate
{
    // ....
}

Answer 1

如果在-beginAnimation中的完成块运行之前调用-endAnimation --也就是说，在0.5秒动画完成之前--您将用新的self.displayLink覆盖旧的self.displayLink。之后，当完成块运行时，您将使新的显示链接失效，而不是旧的链接。

使用中间变量捕获self.displayLink的值，该值保存要使其无效的显示链接。此外，为了更好地度量，当您完成时，将self.displayLink设置为零。

- (void)beginAnimation // triggered by a UIButton
{
    [UIView animateWithDuration:0.5 animations:^{ self.alpha = 1.0; }];

    if (self.displayLink != nil) {
        // You called -beginAnimation before you called -endAnimation.
        // I'm not sure if your code is doing this or not, but if it does,
        // you need to decide how to handle it.
    } else {
        // Make a new display link.
        self.displayLink = [CADisplayLink displayLinkWithTarget:self selector:@selector(rotate)];
        [self.displayLink addToRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
    }
}

- (void)endAnimation // triggered by another UIButton
{
    if (self.displayLink == nil) {
        // You called -endAnimation before -beginAnimation.
        // Again, you need to determine what, if anything,
        // to do in this case.
    } else {
        CADisplayLink oldDisplayLink = self.displayLink;
        self.displayLink = nil;

        [UIView animateWithDuration:0.5 animations:^{ self.alpha = 0.0; } completion:^(BOOL finished) {
            [oldDisplayLink invalidate];
        }];
    }
}