UICollectionView - 在设备旋转上调整单元格大小 - Swift

问题描述

我创建了一个 UICollectionView，以便我可以将视图排列成整齐的列.我希望在宽度大于 500 像素的设备上有一列.

I've created a UICollectionView, so that I can arrange views into neat columns. I'd like there to be a single column on devices > 500 pixels wide.

为了实现这一点，我创建了这个函数:

In order to achieve this, I created this function:

func collectionView(collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAtIndexPath indexPath: NSIndexPath) -> CGSize {
    let size = collectionView.frame.width
    if (size > 500) {
        return CGSize(width: (size/2) - 8, height: (size/2) - 8)
    }
    return CGSize(width: size, height: size)
}

这在第一次加载时按预期工作，但是当我旋转设备时，计算并不总是再次发生，并且视图并不总是按预期重绘.这是我旋转设备时的代码:

This works as expected on first load, however when I rotate the device, the calculation doesn't always happen again, and the views don't always redraw as expected. Here's my code for when the device is rotated:

override func willRotateToInterfaceOrientation(toInterfaceOrientation: UIInterfaceOrientation, duration: NSTimeInterval) {
    collectionView.collectionViewLayout.invalidateLayout()
    self.view.setNeedsDisplay()
}

我假设我忘记重绘某些东西，但我不确定是什么.非常感谢收到任何想法！

I'm assuming I've forgotten to redraw something, but I'm not sure what. Any ideas are very gratefully recieved!

推荐答案

您可以使用 viewWillLayoutSubviews.这个问题应该会有所帮助，但每当视图控制器视图即将布局其子视图时，这都会被调用.

You might use viewWillLayoutSubviews. This question should be helpful but this is bassically called whenever the view controller views is about to layout its subviews.

所以你的代码看起来像这样:

So your code will look like this:

override func viewWillLayoutSubviews() {
  super.viewWillLayoutSubviews()

  guard let flowLayout = collectionView.collectionViewLayout as? UICollectionViewFlowLayout else {
    return
  }

  if UIInterfaceOrientationIsLandscape(UIApplication.sharedApplication().statusBarOrientation) {
    //here you can do the logic for the cell size if phone is in landscape
  } else {
    //logic if not landscape
  }

  flowLayout.invalidateLayout()
}

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