ios - 无法获得更改其大小的 View

Question

我在 ForecastCell Class 中有一个 UIImageView(对于 UICollectionView)，无论如何，我无法获取 UIImageView 在单元格内改变它的大小。这是我尝试过的:

private func setupWeatherIcon(){
    self.addSubview(mWeatherIcon)

   //mWeatherIcon.frame.size.width = CGFloat(self.frame.width) / 2
   //mWeatherIcon.frame.size.height = CGFloat(self.frame.height) / 2
   mWeatherIcon.frame.size.width = 20
   mWeatherIcon.frame.size.height = 20

   mWeatherIcon.centerXAnchor.constraint(equalTo: self.safeAreaLayoutGuide.centerXAnchor).isActive = true
   mWeatherIcon.centerYAnchor.constraint(equalTo: self.safeAreaLayoutGuide.centerYAnchor).isActive = true
}

这是 mWeatherIcon:

var mWeatherIcon: UIImageView = {
    let image = UIImageView(image: UIImage(named: "partly-cloudy"))

    image.translatesAutoresizingMaskIntoConstraints = false
    return image
}()

无论我设置什么宽度和高度，它始终保持相同的宽度和高度。

Answer 1

你需要宽度和高度限制

self.contentView.addSubview(mWeatherIcon)

NSLayoutConstraint.activate([
   mWeatherIcon.centerXAnchor.constraint(equalTo:contentView.centerXAnchor),
   mWeatherIcon.centerYAnchor.constraint(equalTo:contentView.centerYAnchor),
   mWeatherIcon.widthAnchor.constraint(equalTo:contentView.widthAnchor,multiplier:0.5),
   mWeatherIcon.heightAnchor.constraint(equalTo:contentView.heightAnchor,multiplier:0.5)
])

不要忘记实现这个方法

func collectionView(_ collectionView: UICollectionView, 
                  layout collectionViewLayout: UICollectionViewLayout, 
           sizeForItemAt indexPath: IndexPath) -> CGSize