使用 Swift 和 Parse 创建图像预览

Posted 2023-03-11

【中文标题】使用 Swift 和 Parse 创建图像预览

【英文标题】：Creating Image Preview using Swift and Parse

【发布时间】：2015-03-31 23:15:33

【问题描述】：

我目前正在用 Swift 编写一个社交网络应用程序。在我的应用程序中，我有一个功能，用户可以向时间线发送带有附加图像的消息。我希望能够检索图像并使用时间轴内的 UIImageView 预览它。但是，我希望图像显示在发送图像的用户旁边，如果用户没有发布图像，图像预览不会与消息一起出现。我想要的功能的一个很好的例子是 Facebook 和 Twitter 在各自的 ios 应用程序中显示图像的方式。与此同时，我编写了以下函数来检索图像，但我无法将它们与正确的用户匹配。我将在下面发布我的函数以及将源代码下载到我的时间线的链接。在此先感谢

函数加载图像（）

    
        var query = PFQuery(className: "imagesUploaded")
        query.orderByDescending("objectId")
        query.whereKey("user", equalTo:PFUser.currentUser())


        query.findObjectsInBackgroundWithBlock 
            (objects:[AnyObject]!,error:NSError!) -> Void in
            if error == nil 
                let imagesobjects = objects as [PFObject]

                for object : PFObject in objects as [PFObject] 
                    let image = object["filename"] as PFFile

                    image.getDataInBackgroundWithBlock 
                        (imageData:NSData!, error:NSError!) -> Void in
                        if error == nil 
                            if let finalimage = UIImage(data: imageData)
                            
                                let url = image.url
                                println(url)
                                cell.imagedisplay.image = finalimage



                            
                        

                    
                
            
        
        

TimeLine Source Code

【参考方案1】：

我在这门课上做了这个：

import UIKit
import Parse

class postViewController: UIViewController, UINavigationControllerDelegate, UIImagePickerControllerDelegate 

    var photoSelected:Bool = false
    var activityIndicator: UIActivityIndicatorView = UIActivityIndicatorView()

    @IBOutlet weak var imageToPost: UIImageView!
    @IBOutlet weak var shareText: UITextField!

    @IBAction func logout(sender: AnyObject) 
        PFUser.logOut()
        self.performSegueWithIdentifier("logout", sender: "self")
       

    @IBAction func chooseImage(sender: AnyObject) 
        // Creation d'une variable image controlleur
        var image = UIImagePickerController()
        dispatch_async(dispatch_get_main_queue())
        image.delegate = self
        image.sourceType = UIImagePickerControllerSourceType.PhotoLibrary
        image.allowsEditing = false

            self.presentViewController(image, animated: true, completion: nil)
    

    @IBAction func postImage(sender: AnyObject) 
        var error = ""
        if (photoSelected == false)
            error = "Please Select an Image to post"
         else if (shareText.text == "") 
            error = "Please enter a message"
        
        if (error != "")
            displayAlert("Cannot post Image", error: error)
         else 

            activityIndicator = UIActivityIndicatorView(frame: CGRectMake(0, 0, 50, 50))
            // On positione l'indicateur au centre de l'ecran
            activityIndicator.center = self.view.center
            activityIndicator.hidesWhenStopped = true
            activityIndicator.activityIndicatorViewStyle = UIActivityIndicatorViewStyle.Gray
            view.addSubview(activityIndicator)
            activityIndicator.startAnimating()
            UIApplication.sharedApplication().beginIgnoringInteractionEvents()

            var post = PFObject(className: "post")
            post["Title"] = shareText.text
            post["username"] = PFUser.currentUser().username

            post.saveInBackgroundWithBlock(success: Bool, error: NSError!) -> Void in

                if success == false 
                    self.activityIndicator.stopAnimating()
                    UIApplication.sharedApplication().endIgnoringInteractionEvents()

                    self.displayAlert("Could not post Image", error: "Please try again later")

                 else 

                    let imageData = UIImagePNGRepresentation(self.imageToPost.image)
                    let imageFile = PFFile(name: "image.png", data: imageData)

                    post["imageFile"] = imageFile
                    post.saveInBackgroundWithBlock(success: Bool, error: NSError!) -> Void in

                        self.activityIndicator.stopAnimating()
                        UIApplication.sharedApplication().endIgnoringInteractionEvents()

                        if success == false 

                            self.displayAlert("Could not post Image", error: "Please try again later")
                         else 
                            self.displayAlert(" Image Posted !", error: "Your image has been posted successfully")
                            self.photoSelected = false
                            self.imageToPost.image = UIImage(named: "default-placeholder")
                            self.shareText.text = ""
                            println("Posted succesfully")
                        
                    
                
            
        
    

    func displayAlert(title: String, error: String)
        var alert = UIAlertController(title: title, message: error, preferredStyle: UIAlertControllerStyle.Alert)
            alert.addAction(UIAlertAction(title: "Ok", style: .Default, handler: action in
            ))
            self.presentViewController(alert, animated: true, completion: nil)
    

    func imagePickerController(picker: UIImagePickerController, didFinishPickingImage image: UIImage!, editingInfo: [NSObject : AnyObject]!) 
        println("Image is selected!")
        self.dismissViewControllerAnimated(true, completion: nil)

        imageToPost.image = image

        photoSelected = true
    

    override func viewDidLoad() 
        super.viewDidLoad()

        photoSelected = false

        imageToPost.image = UIImage(named: "default-placeholder")

        self.shareText.text = ""
    

    override func didReceiveMemoryWarning() 
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    

    override func touchesBegan(touches: NSSet, withEvent event: UIEvent) 
        self.view.endEditing(true)
    


    func textFiledShouldReturn(textField: UITextField!) -> Bool
        shareText.resignFirstResponder()
        return true
    

编辑：

您可以像这样添加测试：

func imagePickerController(picker: UIImagePickerController, didFinishPickingImage image: UIImage!, editingInfo: [NSObject : AnyObject]!) 

        self.dismissViewControllerAnimated(true, completion: nil)
        initialisationPhoto()

        photoUtilisateur.image = image

        if (photoUtilisateur.image != nil)
            println("Image is selected!")
            photoSelected = true
        
    

func initialisationPhoto()
    //Initialisation de la photo utilisateur
    photoSelected = false
    photoUtilisateur.image = UIImage(named: "placeholder")

【讨论】：

感谢您的代码。我拿了一些并添加到我的课程中，但是在调用图像选择器函数时遇到了可选值的问题。我在下面发布了我的代码。关于如何解决的任何想法？ func imagePickerController(picker: UIImagePickerController!, didFinishPickingImage image: UIImage!, editingInfo: [NSObject : AnyObject]!) println("image selected") self.dismissViewControllerAnimated(true, completion: nil) ImagetoPost.image! = image // 错误在这里 photoSelected = true

我已经编辑了我的答案，看看imagePickerController函数中的测试:)

这是我的代码Screenshot 的屏幕截图，测试功能仍然出现错误。我做错了什么？

嗯，你想用模拟器拍照吗？因为您只能使用设备拍照。使用模拟器，您只能从照片库中获取照片。这是你的问题吗？

是的，当我在物理设备上拍照以及在模拟器中选择照片时会发生错误。只要您点击“使用照片”按钮，应用就会崩溃。