Question

我有一个小按钮可以显示和隐藏UI元素。当我按下主屏幕按钮离开应用程序然后返回到该应用程序时，该按钮跳至其原始位置，而不是其动画设置的新位置。

所需的操作是将其保留在用户离开并回到应用程序时的位置。

@IBAction func hideChartTapped(_ sender: Any) {
    let delay = 0.3
    if chart.isHidden {
        self.chart.isHidden = false
        UIView.animate(withDuration: delay, animations: {
            self.hideChart.center.y = (self.hideChart.center.y - self.chart.bounds.height)
            self.chart.center.y = (self.chart.center.y - self.chart.bounds.height)
        }, completion: nil)
    } else {
        UIView.animate(withDuration: delay, animations: {
            self.hideChart.center.y = (self.hideChart.center.y + self.chart.bounds.height)
            self.chart.center.y = (self.chart.center.y + self.chart.bounds.height)
            self.hideChart.setNeedsDisplay()
        }, completion: nil)
        DispatchQueue.main.asyncAfter(deadline: .now() + delay, execute: {
            self.chart.isHidden = true
        })
    }
}

这是我用来隐藏和显示图表以及移动按钮的代码。按钮和图表的默认位置是在主故事板中设置的。

Answer 1

我知道了。我也没有更新约束。我仍在对中心运动进行动画处理，但是在动画之后，我将重置约束，如下所示：

@IBAction func hideChartTapped(_ sender: Any) {
    let delay = 0.3
    if chart.isHidden {
        self.chart.isHidden = false
        UIView.animateKeyframes(withDuration: delay, delay: 0, options: [], animations: {
            self.hideChart.center.y = (self.hideChart.center.y - self.chart.bounds.height)
            self.chart.center.y = (self.chart.center.y - self.chart.bounds.height)
        }, completion: nil)
        DispatchQueue.main.asyncAfter(deadline: .now() + delay, execute: {
            self.hideChartBottomConstraint.constant = 0
            self.hideChart.layoutIfNeeded()
        })
    } else {
        UIView.animateKeyframes(withDuration: delay, delay: 0, options: [], animations: {
            self.hideChart.center.y = (self.hideChart.center.y + self.chart.bounds.height)
            self.chart.center.y = (self.chart.center.y + self.chart.bounds.height)
        }, completion: nil)
        DispatchQueue.main.asyncAfter(deadline: .now() + delay, execute: {
            self.hideChartBottomConstraint.constant = self.chart.bounds.height
            self.hideChart.layoutIfNeeded()
            self.chart.isHidden = true
        })
    }
}

当应用进入后台时，按钮会跳转位置

1 个答案: