UITableView 内的动态 UIImageView 大小

问题描述

我想用一个显示图像的自定义 TableViewCell 实现一个 TableView.

I want to implement a TableView with a Custom TableViewCell showing an image.

为了简单起见，我只是使用自动布局将 UIImageView 放在 tableviewcell 中(如下图所示).

To make this simple, I simply put a UIImageView inside a tableviewcell using autolayout (illustrated below).

我想要的是在 UIImageView 中显示图像，但是这些图像尺寸可以是任何尺寸并且不一致(纵向、横向、正方形)...

What I want is to display the image inside a UIImageView however those images dimensions can be anything and are inconsistent (portrait, landscape, square) ...

因此，我希望显示具有固定宽度(设备宽度)和符合图像比例的动态高度的图像.我想要这样的东西:

Therefore, I'm looking to display an image with a fixed width (the width of the device) and a dynamic height that respect the ratio of the images. I want something like this:

很遗憾，我没能达到这个结果.

I unfortunately didn't manage to reach that result.

这是我实现它的方式 - (我正在使用 Haneke 从 URL 加载图像 - 图像存储在 Amazon S3 中):

Here's how I implemented it - (I'm using Haneke to load the image from an URL - image stored in Amazon S3):

class TestCellVC: UITableViewCell {

    @IBOutlet weak var selfieImageView: UIImageView!
    @IBOutlet weak var heightConstraint: NSLayoutConstraint!

    func loadItem(#selfie: Selfie) {        
        let selfieImageURL:NSURL = NSURL(string: selfie.show_selfie_pic())!

        self.selfieImageView.hnk_setImageFromURL(selfieImageURL, placeholder: nil, format: HNKFormat<UIImage>(name: "original"), failure: {error -> Void in println(error)
            }, success: { (image) -> Void in
                // Screen Width
                var screen_width = UIScreen.mainScreen().bounds.width

                // Ratio Width / Height
                var ratio =  image.size.height / image.size.width

                // Calculated Height for the picture
                let newHeight = screen_width * ratio

                // METHOD 1
                self.heightConstraint.constant = newHeight

                // METHOD 2
                //self.selfieImageView.bounds = CGRectMake(0,0,screen_width,newHeight)

                self.selfieImageView.image = image
            }
        )
    }

    override func viewDidLoad() {
        super.viewDidLoad()

        // Register the xib for the Custom TableViewCell
        var nib = UINib(nibName: "TestCell", bundle: nil)
        self.tableView.registerNib(nib, forCellReuseIdentifier: "TestCell")

        // Set the height of a cell dynamically
        self.tableView.rowHeight = UITableViewAutomaticDimension
        self.tableView.estimatedRowHeight = 500.0

        // Remove separator line from UITableView
        self.tableView.separatorStyle = UITableViewCellSeparatorStyle.None

        loadData()
    }

    override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
        var cell = tableView.dequeueReusableCellWithIdentifier("TestCell") as TestCellVC


        cell.loadItem(selfie: self.selfies_array[indexPath.row])
        // Remove the inset for cell separator
        cell.layoutMargins = UIEdgeInsetsZero
        cell.separatorInset = UIEdgeInsetsZero

        // Update Cell Constraints
        cell.setNeedsUpdateConstraints()
        cell.updateConstraintsIfNeeded()
        cell.sizeToFit()

        return cell
    }
}

我对动态高度的计算是正确的(我已经打印出来了).我已经尝试了两种方法(在代码中描述)，但都没有奏效:

My calculation of the dynamic Height is correct (I've printed it). I've tried both method (describe in the code) but none of them worked:

1. 设置 UIImageView 的 Height Autolayout 约束
2. 修改 UIImageView 的框架

在此处查看方法 1 和 2 的结果:

See Results of Method 1 and 2 here:

推荐答案

在情节提要中为您的 UIImageView 添加尾随、前导、底部和顶部约束.加载图像后，您需要做的就是向 UIImageView 添加一个方面约束.您的图像单元格看起来像这样:

In the storyboard add trailing, leading, bottom and top constraints to your UIImageView. After you load your image all you need to do is add an aspect constraint to your UIImageView. Your images cell would look something like this:

class ImageTableViewCell: UITableViewCell {

    @IBOutlet weak var customImageView: UIImageView!

    internal var aspectConstraint : NSLayoutConstraint? {
        didSet {
            if oldValue != nil {
                customImageView.removeConstraint(oldValue!)
            }
            if aspectConstraint != nil {
                customImageView.addConstraint(aspectConstraint!)
            }
        }
    }

    override func prepareForReuse() {
        super.prepareForReuse()
        aspectConstraint = nil
    }

    func setCustomImage(image : UIImage) {

        let aspect = image.size.width / image.size.height

        let constraint = NSLayoutConstraint(item: customImageView, attribute: NSLayoutAttribute.width, relatedBy: NSLayoutRelation.equal, toItem: customImageView, attribute: NSLayoutAttribute.height, multiplier: aspect, constant: 0.0)
        constraint.priority = 999

        aspectConstraint = constraint

        customImageView.image = image
    }
}

您可以在此处查看工作示例 DynamicTableWithImages

You can check working example here DynamicTableWithImages

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