UIDatePicker 更改事件不会在第一次旋转 Swift 时触发 [英] UIDatePicker change event not firing on first spin Swift

问题描述

我正在尝试在用户更新 UIDatePicker(倒数计时器)时更新标签.但是，它仅在第一次旋转后更新它.第一次旋转不会改变标签值.我试图在主队列上执行 UI 更新但无济于事.

I am trying to update a label when the UIDatePicker (Count Down Timer) is updated by the user. However, it only updates it after the first spin. The first spin does not change the label value. I have attempted to perform the UI update on the main queue to no avail.

推荐答案

这是一个众所周知且长期存在的错误.如果您仔细观察 Apple 使用倒计时日期选择器的项目(如时钟应用程序的 Timer 部分)，他们从不尝试响应旋转选择器的动作；用户必须点击一个按钮，然后读取选择器的值.我建议你设计你的界面类似.

This is a well-known and long-standing bug. If you look closely at Apple's projects that use a count down date picker (like the Timer part of the Clock app), they never try to respond to the action of spinning the picker; the user has to tap a button which then reads the value of the picker. I suggest you design your interface similarly.

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