带有大标题的导航栏 iOS 11 的图像

AppStore app has an icon with an image on the right side of the NabBar with Large Title:

如果有人的话我真的很感激知道如何实施 it or ideas关于如何去做。

BTW: Setting an image for UIButton inside of UIBarButtonItem won't work. Tried already. The button sticks to the top of the screen:

经过几个小时的编码，我终于成功了让它起作用。我也决定写一篇详细教程: link https://blog.uptech.team/how-to-build-resizing-image-in-navigation-bar-with-large-title-8ba2e8bcb840。如果您更喜欢非常详细的说明，请遵循它。

Demo:

GitHub 上的完整项目：link https://github.com/tungfam/ImageInNavigationBarDemo.

这里有5 steps来完成它：

第 1 步：创建图像

private let imageView = UIImageView(image: UIImage(named: "image_name"))

第 2 步：添加常量

/// WARNING: Change these constants according to your project's design
private struct Const {
    /// Image height/width for Large NavBar state
    static let ImageSizeForLargeState: CGFloat = 40
    /// Margin from right anchor of safe area to right anchor of Image
    static let ImageRightMargin: CGFloat = 16
    /// Margin from bottom anchor of NavBar to bottom anchor of Image for Large NavBar state
    static let ImageBottomMarginForLargeState: CGFloat = 12
    /// Margin from bottom anchor of NavBar to bottom anchor of Image for Small NavBar state
    static let ImageBottomMarginForSmallState: CGFloat = 6
    /// Image height/width for Small NavBar state
    static let ImageSizeForSmallState: CGFloat = 32
    /// Height of NavBar for Small state. Usually it's just 44
    static let NavBarHeightSmallState: CGFloat = 44
    /// Height of NavBar for Large state. Usually it's just 96.5 but if you have a custom font for the title, please make sure to edit this value since it changes the height for Large state of NavBar
    static let NavBarHeightLargeState: CGFloat = 96.5
}

第三步：设置用户界面：

private func setupUI() {
    navigationController?.navigationBar.prefersLargeTitles = true

    title = "Large Title"

    // Initial setup for image for Large NavBar state since the the screen always has Large NavBar once it gets opened
    guard let navigationBar = self.navigationController?.navigationBar else { return }
    navigationBar.addSubview(imageView)
    imageView.layer.cornerRadius = Const.ImageSizeForLargeState / 2
    imageView.clipsToBounds = true
    imageView.translatesAutoresizingMaskIntoConstraints = false
    NSLayoutConstraint.activate([
        imageView.rightAnchor.constraint(equalTo: navigationBar.rightAnchor,
                                         constant: -Const.ImageRightMargin),
        imageView.bottomAnchor.constraint(equalTo: navigationBar.bottomAnchor,
                                          constant: -Const.ImageBottomMarginForLargeState),
        imageView.heightAnchor.constraint(equalToConstant: Const.ImageSizeForLargeState),
        imageView.widthAnchor.constraint(equalTo: imageView.heightAnchor)
        ])
}

第四步：创建图像调整大小方法

private func moveAndResizeImage(for height: CGFloat) {
    let coeff: CGFloat = {
        let delta = height - Const.NavBarHeightSmallState
        let heightDifferenceBetweenStates = (Const.NavBarHeightLargeState - Const.NavBarHeightSmallState)
        return delta / heightDifferenceBetweenStates
    }()

    let factor = Const.ImageSizeForSmallState / Const.ImageSizeForLargeState

    let scale: CGFloat = {
        let sizeAddendumFactor = coeff * (1.0 - factor)
        return min(1.0, sizeAddendumFactor + factor)
    }()

    // Value of difference between icons for large and small states
    let sizeDiff = Const.ImageSizeForLargeState * (1.0 - factor) // 8.0

    let yTranslation: CGFloat = {
        /// This value = 14. It equals to difference of 12 and 6 (bottom margin for large and small states). Also it adds 8.0 (size difference when the image gets smaller size)
        let maxYTranslation = Const.ImageBottomMarginForLargeState - Const.ImageBottomMarginForSmallState + sizeDiff
        return max(0, min(maxYTranslation, (maxYTranslation - coeff * (Const.ImageBottomMarginForSmallState + sizeDiff))))
    }()

    let xTranslation = max(0, sizeDiff - coeff * sizeDiff)

    imageView.transform = CGAffineTransform.identity
        .scaledBy(x: scale, y: scale)
        .translatedBy(x: xTranslation, y: yTranslation)
}

Step 5:

override func scrollViewDidScroll(_ scrollView: UIScrollView) {
    guard let height = navigationController?.navigationBar.frame.height else { return }
    moveAndResizeImage(for: height)
}

希望它很清楚并对您有所帮助！ 如果您还有任何其他问题，请在评论中告诉我。