将图像从集合视图控制器快速传递到另一个视图控制器

Posted 2023-03-12

【中文标题】将图像从集合视图控制器快速传递到另一个视图控制器

【英文标题】：swift pass images from collection view controller to another view controller

【发布时间】：2017-06-16 04:02:28

【问题描述】：

我已经从 firebase 下载了一组用户照片并将其作为收藏视图查看（类似 instagram） 但我试图放大使用 segue 在另一个视图控制器中单击的照片，但它不起作用。 关于我的代码的任何想法：

class ProfileViewController: UIViewController
    var photoThumbnail: UIImage! 
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell 

        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "collection_cell", for: indexPath) as! ProfileCollectionViewCell
        cell.imageCollection.downloadImage2(from: currPosts[indexPath.row].photoUrl)
        cell.imageCollection.image = photoThumbnail
        return cell
    

    func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) 
        performSegue(withIdentifier: "photoViewSegue", sender: nil)
    

    override func prepare(for segue: UIStoryboardSegue, sender: Any?) 
        var destViewController : EnlargePhotoViewController = segue.destination as! EnlargePhotoViewController
        destViewController.labelText = "test"  //**** this works
        destViewController.myImage = photoThumbnail //**** this doesnt work 
    

集合视图单元格是：

class ProfileCollectionViewCell: UICollectionViewCell 
    @IBOutlet weak var imageCollection: UIImageView!

最后是目标viewController：

class EnlargePhotoViewController: UIViewController 

        @IBOutlet weak var myLabel: UILabel!
        @IBOutlet weak var enlargedPhoto: UIImageView!

        var labelText = String()
        var myImage: UIImage!

        override func viewDidLoad() 
            super.viewDidLoad()

           myLabel.text = labelText
            enlargedPhoto.image = myImage
        
    

【问题讨论】：

*它不是完整的代码，但我分享了最重要的几行

如果没有看到所有代码，很难知道如何回答这个问题，在摘录中提供的变量 photoThumbnail 从未设置并且始终为零。

【参考方案1】：

尝试改成这段代码：

func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) 
    let cell = collectionView.cellForItem(at: indexPath) as! ProfileCollectionViewCell

    photoThumbnail = cell.imageCollection.image
    performSegue(withIdentifier: "photoViewSegue", sender: nil)

【参考方案2】：

您唯一的目标是获取所选单元格的图像，这可以更有效地完成。你所要做的就是读/写单元格的 imageView 属性，photoThumbnail 永远不会设置所以总是 nil，只需修改这个

func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell 

    let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "collection_cell", for: indexPath) as! ProfileCollectionViewCell
    cell.imageCollection.downloadImage2(from: currPosts[indexPath.row].photoUrl)
    //cell.imageCollection.image = photoThumbnail <-- No need of this
    return cell


func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) 


  // get the correct cell on select 
   if let cell = collectionView.cellForItem(at: indexPath) as! ProfileCollectionViewCell
   
    photoThumbnail =  cell.imageCollection.image <-- finally assign the imageview to image
    performSegue(withIdentifier: "photoViewSegue", sender: self)
   

为了更安全地检索图像，请使用like

 override func viewDidLoad() 
        super.viewDidLoad()


        if let getImage = myImage
        
        myLabel.text = labelText
        enlargedPhoto.image = getImage 
        
    

【参考方案3】：

第一个视图控制器

func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) 
        if indexPath.row == 0
        
            let objstory = storyboard?.instantiateViewController(withIdentifier: "SecondViewController") as! SecondViewController
        objstory.strd = imageView.image
        _ = self.navigationController?.pushViewController(objstory, animated: true)

        
    

SecondViewController

 var strd:UIImage!
@IBOutlet weak var imgprof: UIImageView!

    override func viewDidLoad() 
        super.viewDidLoad()

        imgprof.image = strd


        // Do any additional setup after loading the view.
    

【参考方案4】：

class ProfileViewController: UIViewController
    var photoThumbnail: UIImage!
    var selectedPhotoURL: NSUrl!


func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell 

        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "collection_cell", for: indexPath) as! ProfileCollectionViewCell
        cell.imageCollection.downloadImage2(from: currPosts[indexPath.row].photoUrl)
        cell.imageCollection.image = photoThumbnail
        return cell
    

    func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) 
        selectedPhotoURL = currPosts[indexPath.row].photoUrl
        performSegue(withIdentifier: "photoViewSegue", sender: nil)
    

    override func prepare(for segue: UIStoryboardSegue, sender: Any?) 
        var destViewController : EnlargePhotoViewController = segue.destination as! EnlargePhotoViewController
        destViewController.labelText = "test"  //**** this works
        //make image from selected url or pass url and download it in EnlargePhotoViewController
        let downlodedImage = yourMethodToDownload(selectedPhotoURL) 
        destViewController.myImage = downlodedImage //**** this will work work 
    

【讨论】：

但是我已经下载了图像，如果我再次下载它，那将是糟糕的内存管理。不过谢谢