为什么animateWithDuration动画和完成块之间的暂停？

Question

继苹果公司的建议,我通过把后续调用链接的UIView动画-animationWithDuration:animation:中的completion:另一个呼叫的块aanimateWithDuration:animation:completion:,像这样:

[UIView animateWithDuration:scaleDuration delay:0 options:UIViewAnimationOptionCurveEaseIn animations:^{
    // Scale the controllers' views down.
    self.view.transform = CGAffineTransformScale(self.view.transform, 0.8, 0.8);
} completion:^(BOOL finished) {
    // Transition to the new view and push on the new view controller.
    [UIView transitionWithView:self.view duration:1 options:UIViewAnimationOptionCurveLinear | UIViewAnimationOptionTransitionFlipFromLeft animations:^{
        [self pushViewController:viewController animated:NO];
    } completion:^(BOOL finished) {
        [UIView animateWithDuration:scaleDuration delay:0 options:UIViewAnimationOptionCurveLinear animations:
^{
            // Scale back to the original size.
            self.view.transform = CGAffineTransformScale(self.view.transform, 1.25, 1.25);
        } completion:nil];
    }];
}];

动画都执行正确的顺序,但它们之间存在微小的延迟,特别是在-transitionWithView:duration:options:animations:completion:通话之前.如何平滑动画步骤之间的过渡？

Answer 1

旁白： \n您以这种方式滥用导航控制器
有什么特殊原因吗？\xe2\x80\x99 不能presentViewController:animated:completion:将其过渡样式设置为 吗UIModalTransitionStyleFlipHorizontal？

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回到你的问题：

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I\xe2\x80\x99m 非常确定口吃来自一个简单的事实，即pushViewController:animated:隐式必须加载要推送的视图控制器的视图，并且这需要一些时间。

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因此，如果您无法使用presentViewController:animated:completion:（或presentModalViewController：animated：如果您必须支持iOS 4）方法，我\xe2\x80\x99d鼓励您尝试以下方法：

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// ensure the view is already loaded when you invoke `pushViewController:animated:`\n[viewController view];\n\n// there is no strict need to calculate those in situ, so we do it up front\nCGAffineTransform originalTransform = self.view.transform;\nCGAffineTransform downscalingTransform = CGAffineTransformScale(originalTransform, 0.8, 0.8);\n\n// I found it hard to read the block-in-a-block-in-a... while editing here, so I've taken them apart:\nvoid (^scaleDownAnimation)() = ^{\n    self.view.transform = downscalingTransform;\n};\n\nvoid (^restoreScaleAnimation)() = ^{\n    self.view.transform = originalTransform;\n};\n\nvoid (^pushControllerAnimation)() = ^{\n    [self pushViewController:viewController animated:NO];\n};\n\nvoid (^pushAnimationCompletion)(BOOL) = ^(BOOL unused) {\n    [UIView animateWithDuration:scaleDuration\n                          delay:0\n                        options:UIViewAnimationOptionCurveLinear\n                     animations:restoreScaleAnimation\n                     completion:nil];\n};\n\nvoid (^downscaleCompletion)(BOOL) = ^(BOOL unused){\n    UIViewAnimationOptions linearFlipFromLeft = UIViewAnimationOptionCurveLinear | UIViewAnimationOptionTransitionFlipFromLeft;\n    [UIView transitionWithView:self.view\n                      duration:1\n                       options:linearFlipFromLeft\n                    animations:pushControllerAnimation\n                    completion:pushAnimationCompletion];\n};\n\n[UIView animateWithDuration:scaleDuration\n                      delay:0\n                    options:UIViewAnimationOptionCurveEaseIn\n                 animations:scaleDown\n                 completion:downscaleCompletion];\n

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请注意，牛肉位于前六行内，其余的只是为了完整性。

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