iphone - presentationLayer 值在动画期间不更新？

Question

答案很可能是我无法按照我尝试的方式混合事物，我会接受“正确的方式”来混合事物(可能是更复杂的 CAAnimation？我不知道)。我有什么:

__block BOOL animationComplete = FALSE;
[[UIApplication sharedApplication] beginIgnoringInteractionEvents];
[UIView animateWithDuration:0.5f delay:0.0f options:UIViewAnimationCurveEaseInOut
    animations:^{
        [self setFrame:destRect];
    }
    completion:^(BOOL finished) {
        animationComplete = YES;
        [[UIApplication sharedApplication] endIgnoringInteractionEvents];
    }];

然后轮询:

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_LOW, (unsigned long)NULL), ^{
    while (!animationComplete) {
        CALayer *layer = self.layer.presentationLayer;
        CGRect frame = [layer frame];
        CGPoint point = [layer position];
        float currentTranslation = [[layer valueForKeyPath:@"transform.translation.x"] floatValue];
        NSLog(@"%.1f : %.1f : %.1f : %.1f : %.1f : %.1f",frame.origin.x, currentTranslation, frame.origin.x, layer.bounds.origin.x, layer.position.x, point.x);
    }
});

我是不是抓错队列了？参数错误？我看错层了吗？上面是我尝试查看的值的散点图，在动画期间所有值都没有改变....

214.4 : 0.0 : 214.4 : 0.0 : 264.4 : 264.4
214.4 : 0.0 : 214.4 : 0.0 : 264.4 : 264.4
214.4 : 0.0 : 214.4 : 0.0 : 264.4 : 264.4
214.4 : 0.0 : 214.4 : 0.0 : 264.4 : 264.4
214.4 : 0.0 : 214.4 : 0.0 : 264.4 : 264.4

等:)

Answer 1

您只能在主线程上与 View 层次结构进行交互。您不应该在全局调度队列上调用 self.layer。您只能在 dispatch_get_main_queue() 上执行此操作。

您将不得不重写您的日志记录，使其不再像那样循环，因为完成 block 也在主线程上运行，如果您的 block 正在运行，它就无法运行。

更新

问题肯定是非主线程访问层导致的。我用 View 子类 MyView 创建了一个测试项目。我给了它这个方法:

- (IBAction)move {
    CGRect destRect = self.frame;
    destRect.origin.x = 300 - destRect.origin.x;

    __block BOOL animationComplete = FALSE;
    [[UIApplication sharedApplication] beginIgnoringInteractionEvents];
    [UIView animateWithDuration:0.5f delay:0.0f options:UIViewAnimationCurveEaseInOut
                     animations:^{
                         [self setFrame:destRect];
                     }
                     completion:^(BOOL finished) {
                         animationComplete = YES;
                         [[UIApplication sharedApplication] endIgnoringInteractionEvents];
                     }];

    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_LOW, (unsigned long)NULL), ^{
        while (!animationComplete) {
            dispatch_sync(dispatch_get_main_queue(), ^{
                CALayer *layer = self.layer.presentationLayer;
                CGRect frame = [layer frame];
                CGPoint point = [layer position];
                float currentTranslation = [[layer valueForKeyPath:@"transform.translation.x"] floatValue];
                NSLog(@"%.1f : %.1f : %.1f : %.1f : %.1f : %.1f",frame.origin.x, currentTranslation, frame.origin.x, layer.bounds.origin.x, layer.position.x, point.x);
            });
        }
    });
}

当这个方法运行时，我得到这样的输出:

2012-09-10 21:06:31.732 presentationLayerTest[1274:c07] 20.0 : 0.0 : 20.0 : 0.0 : 100.0 : 100.0
2012-09-10 21:06:31.735 presentationLayerTest[1274:c07] 20.0 : 0.0 : 20.0 : 0.0 : 100.0 : 100.0
2012-09-10 21:06:31.737 presentationLayerTest[1274:c07] 20.0 : 0.0 : 20.0 : 0.0 : 100.0 : 100.0
2012-09-10 21:06:31.737 presentationLayerTest[1274:c07] 20.0 : 0.0 : 20.0 : 0.0 : 100.0 : 100.0
2012-09-10 21:06:31.738 presentationLayerTest[1274:c07] 20.0 : 0.0 : 20.0 : 0.0 : 100.0 : 100.0
2012-09-10 21:06:31.739 presentationLayerTest[1274:c07] 20.0 : 0.0 : 20.0 : 0.0 : 100.0 : 100.0
2012-09-10 21:06:31.739 presentationLayerTest[1274:c07] 20.1 : 0.0 : 20.1 : 0.0 : 100.1 : 100.1
2012-09-10 21:06:31.740 presentationLayerTest[1274:c07] 20.1 : 0.0 : 20.1 : 0.0 : 100.1 : 100.1
2012-09-10 21:06:31.741 presentationLayerTest[1274:c07] 20.1 : 0.0 : 20.1 : 0.0 : 100.1 : 100.1
2012-09-10 21:06:31.741 presentationLayerTest[1274:c07] 20.1 : 0.0 : 20.1 : 0.0 : 100.1 : 100.1
2012-09-10 21:06:31.742 presentationLayerTest[1274:c07] 20.1 : 0.0 : 20.1 : 0.0 : 100.1 : 100.1
2012-09-10 21:06:31.743 presentationLayerTest[1274:c07] 20.1 : 0.0 : 20.1 : 0.0 : 100.1 : 100.1
2012-09-10 21:06:31.743 presentationLayerTest[1274:c07] 20.2 : 0.0 : 20.2 : 0.0 : 100.2 : 100.2
2012-09-10 21:06:31.744 presentationLayerTest[1274:c07] 20.2 : 0.0 : 20.2 : 0.0 : 100.2 : 100.2
2012-09-10 21:06:31.745 presentationLayerTest[1274:c07] 20.2 : 0.0 : 20.2 : 0.0 : 100.2 : 100.2
2012-09-10 21:06:31.745 presentationLayerTest[1274:c07] 20.2 : 0.0 : 20.2 : 0.0 : 100.2 : 100.2

...等等，X 值最终达到 280。

然后我注释掉了 dispatch_sync 行，所以层访问和日志记录发生在全局低优先级线程上，我得到如下输出:

2012-09-10 21:08:20.973 presentationLayerTest[1296:1b03] 20.0 : 0.0 : 20.0 : 0.0 : 100.0 : 100.0
2012-09-10 21:08:20.976 presentationLayerTest[1296:1b03] 20.0 : 0.0 : 20.0 : 0.0 : 100.0 : 100.0
2012-09-10 21:08:20.976 presentationLayerTest[1296:1b03] 20.0 : 0.0 : 20.0 : 0.0 : 100.0 : 100.0
2012-09-10 21:08:20.977 presentationLayerTest[1296:1b03] 20.0 : 0.0 : 20.0 : 0.0 : 100.0 : 100.0
2012-09-10 21:08:20.978 presentationLayerTest[1296:1b03] 20.0 : 0.0 : 20.0 : 0.0 : 100.0 : 100.0
2012-09-10 21:08:20.978 presentationLayerTest[1296:1b03] 20.0 : 0.0 : 20.0 : 0.0 : 100.0 : 100.0
2012-09-10 21:08:20.979 presentationLayerTest[1296:1b03] 20.0 : 0.0 : 20.0 : 0.0 : 100.0 : 100.0
2012-09-10 21:08:20.980 presentationLayerTest[1296:1b03] 20.0 : 0.0 : 20.0 : 0.0 : 100.0 : 100.0
2012-09-10 21:08:20.981 presentationLayerTest[1296:1b03] 20.0 : 0.0 : 20.0 : 0.0 : 100.0 : 100.0
2012-09-10 21:08:20.981 presentationLayerTest[1296:1b03] 20.0 : 0.0 : 20.0 : 0.0 : 100.0 : 100.0
2012-09-10 21:08:20.982 presentationLayerTest[1296:1b03] 20.0 : 0.0 : 20.0 : 0.0 : 100.0 : 100.0
2012-09-10 21:08:20.982 presentationLayerTest[1296:1b03] 20.0 : 0.0 : 20.0 : 0.0 : 100.0 : 100.0
2012-09-10 21:08:20.983 presentationLayerTest[1296:1b03] 20.0 : 0.0 : 20.0 : 0.0 : 100.0 : 100.0
2012-09-10 21:08:20.984 presentationLayerTest[1296:1b03] 20.0 : 0.0 : 20.0 : 0.0 : 100.0 : 100.0

...等等，X 值永远不会改变。