"推送QUOT; Objective-C中的动画 [英] "Push" animation in Objective-C
问题描述
我有两个视图：A和B. A位于屏幕顶部，B位于屏幕底部。
I have two views: A and B. A is positioned at the top of the screen, B is positioned at the bottom of the screen.
当用户按下按钮时，使用EaseInEaseOut bezier曲线向上查看B动画，直到达到y = 0.当B正在前往目的地时，它应该当它击中A时向上推A。换句话说，当B在从底部到顶部的过渡期间经过某个y坐标（A的y原点+高度）时，A应该粘在B上，所以看起来B向上推A。
When the user presses a button, view B animates upwards with a EaseInEaseOut bezier curve until it reaches y = 0. While B is on its way to its destination, it should push A up when it hits A. In other words, when B has passed a certain y coordinate (A's y origin + height) during its transition from bottom to top, A should stick to B so it seems B pushes A upwards.
到目前为止我尝试过：
- 将目标+选择器注册到CADisplayLink用户按下按钮后立即。在此选择器内，通过访问其presentationLayer请求视图B的y坐标，并相应地调整A的y坐标。然而，这种方法结果不够准确：presentationLayer的帧落后于B在屏幕上的当前位置（这可能是因为-presentationLayer重新计算动画视图在当前时间的位置，这需要超过1帧） 。当我增加B的动画持续时间时，此方法可以正常工作。
- 在用户按下按钮后立即将目标+选择器注册到CADisplayLink。在此选择器内，通过求解x =经过时间/动画持续时间（应该返回行进的距离/总距离）的贝塞尔方程来计算B的当前y坐标。我使用了Apple的开源UnitBezier.h（ http： //opensource.apple.com/source/WebCore/WebCore-955.66/platform/graphics/UnitBezier.h ）。但是，结果不正确。
- Register a target + selector to a CADisplayLink immediately after the user pressed the button. Inside this selector, request view B's y coordinate by accessing its presentationLayer and adjust A's y coordinate accordingly. However, this method turns out to be not accurate enough: the presentationLayer's frame is behind on B's current position on the screen (this is probably because -presentationLayer recalculates the position of the animating view on the current time, which takes longer than 1 frame). When I increase B's animation duration, this method works fine.
- Register a target + selector to a CADisplayLink immediately after the user pressed the button. Inside this selector, calculate B's current y coordinate by solving the bezier equation for x = elapsed time / animation duration (which should return the quotient distance traveled / total distance). I used Apple's open source UnitBezier.h for this (http://opensource.apple.com/source/WebCore/WebCore-955.66/platform/graphics/UnitBezier.h). However, the results are not correct.
有关我接下来可以尝试的建议吗？
Any suggestions on what I can try next?
推荐答案
你说你试过动画B并使用显示链接来更新A技术，并且它导致A落后于B。理论上你可以为新视图设置动画C，然后在显示链接中相应地调整B和A的帧，这应该消除任何延迟（相对于彼此）。
You said that you tried the "animate B and use display link to update A" technique, and that it resulted in "A" lagging behind "B". You could theoretically animate a new view, "C", and then adjust B and A's frames accordingly in the display link, which should eliminate any lag (relative to each other).
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