iphone - 如果在添加 subview 后直接将 CATransition 添加到 subview 的图层，为什么 CATransition 不起作用？

Question

出于某种原因，如果在添加 subview 后直接将动画添加到 subview 的图层，则 CATransition 将不会设置动画:

transitionView = [[UIView alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
[transitionView setBackgroundColor:[UIColor redColor]];
[[self contentView] addSubview:transitionView];

CATransition *animation = [CATransition animation];
[animation setDelegate:self];
[animation setType:@"cube"];
[animation setDuration:1.0];
[animation setTimingFunction:[CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseIn]];
[animation setSubtype:@"fromRight"];

[[transitionView layer] addAnimation:animation forKey:nil];

但是如果动画是在稍微延迟后添加的:

transitionView = [[UIView alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
[transitionView setBackgroundColor:[UIColor redColor]];
[[self contentView] addSubview:transitionView];

CATransition *animation = [CATransition animation];
[animation setDelegate:self];
[animation setType:@"cube"];
[animation setDuration:1.0];
[animation setTimingFunction:[CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseIn]];
[animation setSubtype:@"fromRight"];

[self performSelector:@selector(animate) withObject:nil afterDelay:0.00001];

-

- (void)animate
{
    CATransition *animation = [CATransition animation];
    [animation setDelegate:self];
    [animation setType:@"cube"];
    [animation setDuration:1.0];
    [animation setTimingFunction:[CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseIn]];
    [animation setSubtype:@"fromRight"];

    [[transitionView layer] addAnimation:animation forKey:nil];
}

过渡将按预期进行。这有什么原因吗？

Answer 1

我也见过这种行为。我认为这是因为该层位于您可以访问的“模型”层层次结构中，但尚未将其添加到代表屏幕上实际内容的“真实”数据结构中。

无论如何，您可以通过使用 [CATransactionlush] 来解决这个问题，如下所示:

transitionView = [[UIView alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
[transitionView setBackgroundColor:[UIColor redColor]];
[[self contentView] addSubview:transitionView];

// Synchronize the implementation details with my changes so far.
[CATransaction flush];

CATransition *animation = [CATransition animation];
[animation setDelegate:self];
[animation setType:@"cube"];
[animation setDuration:1.0];
[animation setTimingFunction:[CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseIn]];
[animation setSubtype:@"fromRight"];

[[transitionView layer] addAnimation:animation forKey:nil];