Question

我试图动态淡化PageViewController中的背景色。我想将页面上的颜色淡化为另一种颜色。

到目前为止，我尝试通过实现函数scrollView并设置PageViewController的背景色来利用scrollViewDidScroll的基础scrollview。

看看下面的代码：

func scrollViewDidScroll(_ scrollView: UIScrollView) {
    let offset = scrollView.contentOffset.x
    guard lowerIndex >= 0, upperIndex < colors.count else { return }
    let percentComplete = (offset / CGFloat(colors.count)) / (scrollView.frame.width / CGFloat(colors.count))
    scrollView.backgroundColor = fadeFromColor(fromColor: colorCurrent, toColor: colorAfter, withPercentage: percentComplete)
}

此函数使用自定义函数fadeFromColor，其定义如下：

func fadeFromColor(fromColor: UIColor, toColor: UIColor, withPercentage: CGFloat) -> UIColor {
    var fromRed: CGFloat = 0.0
    var fromGreen: CGFloat = 0.0
    var fromBlue: CGFloat = 0.0
    var fromAlpha: CGFloat = 0.0

    fromColor.getRed(&fromRed, green: &fromGreen, blue: &fromBlue, alpha: &fromAlpha)

    var toRed: CGFloat = 0.0
    var toGreen: CGFloat = 0.0
    var toBlue: CGFloat = 0.0
    var toAlpha: CGFloat = 0.0

    toColor.getRed(&toRed, green: &toGreen, blue: &toBlue, alpha: &toAlpha)

    // calculate the actual RGBA values of the fade colour
    let red = (toRed - fromRed) * withPercentage + fromRed
    let green = (toGreen - fromGreen) * withPercentage + fromGreen
    let blue = (toBlue - fromBlue) * withPercentage + fromBlue
    let alpha = (toAlpha - fromAlpha) * withPercentage + fromAlpha

    // return the fade colour
    return UIColor(red: red, green: green, blue: blue, alpha: alpha)
}

目前，我无法在正确的时间获得正确的颜色。您有更好的主意来解决我的问题吗？还是您认为至少我的想法是正确的？

如何动态更改PageViewController中的背景？

0 个答案: