ios13 Dark Mode change not recognized by tableview

问题:

I'm checking my existing app to work correctly with the new introduced dark mode feature of ios 13.

Everything seems to work fine, only the cell background in one of my tableViews is not refreshed according the mode (dark / light).

If the app starts in dark mode, the cells also show the correct dark background. If the mode changes while the app is in background, the cell background color is not changed. The cell label switches the color correct.

for the tableview cells i use the following func for a gradient:

func gradient(frame:CGRect) -> CAGradientLayer { 

    let gradColor1 = UIColor(named: "gradientBright")!
    let gradColor2 = UIColor(named: "gradientDark")!

    let layer = CAGradientLayer()
    layer.frame = frame
    layer.startPoint = CGPoint(x: 0.5, y: 0)
    layer.endPoint = CGPoint(x: 0.5, y: 1)
    layer.colors = [
        gradColor1.cgColor,
        gradColor2.cgColor
    ]
    layer.shadowOpacity = 0.7
    layer.shadowRadius = 10.0
    return layer
}

i add the gradient background to the table cells in

override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {

with the following code

cell.layer.insertSublayer(gradient(frame: cell.bounds), at: 0)

Any idea, why only the gradient func does not seem to get the correct colors after a mode change happened while app active or in background?

Regards

回答1:

Cell will detect, layer will not! You must manually update all layer adaptations in the cell for example.

override func traitCollectionDidChange(_ previousTraitCollection: UITraitCollection?) {
    super.traitCollectionDidChange(previousTraitCollection)

    if traitCollection.hasDifferentColorAppearance(comparedTo: previousTraitCollection) {
        removeAndReaddGradientIfNeeded()
    }
}

More description here

回答2:

If this gradient is on every cell of this type, then it should simply be a part of the cell, not inserted by the containing view controller. Then, in your cell, you can implement:

override func traitCollectionDidChange(_ previousTraitCollection: UITraitCollection?) {
  super.traitCollectionDidChange(previousTraitCollection)

  if traitCollection.userInterfaceStyle != previousTraitCollection?.userInterfaceStyle {
    // reload the gradient layer to react
  }
}

You could also implement this in your view controller and reload data but it's messier.