Swift - 从解析接收图像并显示它们的问题

Question

我在从解析中获取用户图像并将它们加载到表格视图时遇到问题。我认为这与 userId /Strings 和指针业务有关！

图片上传很好解析，我可以看到它们，但我似乎无法下载它们。我的代码绝对是问题所在，我只是不知道是哪一部分。

解析时，userId 是一个指向用户类的指针，所以我很确定我在连接它时做错了..！我是 swift & Parse 的新手，所以我仍然很难理解这一切。

下面是我的代码，如果有人理解这个问题，如果你能告诉我，我会很高兴的！！

import UIKit 
import Parse 

class TimelineTableViewController: UITableViewController, UIImagePickerControllerDelegate, UINavigationControllerDelegate, UIPopoverPresentationControllerDelegate { 

@IBOutlet var feedTableView: UITableView! 
var refresher:UIRefreshControl! 

var titles = [String]() 
var username = [String]() 
var imageFiles = [PFFile]() 
var users = [String: String]() 



override func viewDidLoad() { 
super.viewDidLoad() 

let query = PFUser.query() 
query?.findObjectsInBackgroundWithBlock({ (objects, error) -> Void in 
if let users = objects { 
self.titles.removeAll(keepCapacity: true) 
self.imageFiles.removeAll(keepCapacity: true) 
self.users.removeAll(keepCapacity: true) 
self.username.removeAll(keepCapacity: true) 
for object in users { 
if let user = object as? PFUser { 
self.users[user.objectId!] = user.username! 

} 
} 
} 



let getFollowedUsersQuery = PFQuery(className: "followers") 
getFollowedUsersQuery.whereKey("follower", equalTo: PFUser.currentUser()!) 
getFollowedUsersQuery.findObjectsInBackgroundWithBlock { (objects, error) -> Void in 
if let objects = objects { 
for object in objects { 
let followedUser = object ["following"] as! String 
let query = PFQuery(className: "Post") 
query.whereKey("userId", equalTo: followedUser) 
query.findObjectsInBackgroundWithBlock({ (objects, error) -> Void in 
if let objects = objects { 
for object in objects { 
self.titles.append(object["title"]! as! String) 
self.imageFiles.append(object["imageFile"]! as! PFFile) 
self.username.append(self.users[object["userId"] as! String]!) 
self.tableView.reloadData() 


} }}) } } } }) 

// Add the refresher 
refresher = UIRefreshControl() 
refresher.attributedTitle = NSAttributedString(string: "") 
refresher.addTarget(self, action: "refreshData", forControlEvents: UIControlEvents.ValueChanged) 
// Add the refresher as a sub view on the tableview 
self.feedTableView.addSubview(refresher) 


} 


func refreshData() -> Void { 
self.refresher.endRefreshing()} 

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


@IBAction func blogPost(sender: AnyObject) { 

} 


@IBAction func CameraPopover(sender: AnyObject) { 

self.performSegueWithIdentifier("cameraPopover", sender: self) 

} 


override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) { 

if segue.identifier == "cameraPopover" 
{ 
let vc = segue.destinationViewController 
let controller = vc.popoverPresentationController 

if controller != nil 

{ 
controller?.delegate = self 
vc.preferredContentSize = CGSizeMake(50, 90) 
} 

}} 

func adaptivePresentationStyleForPresentationController(controller: UIPresentationController) -> UIModalPresentationStyle { 

return.None 
} 

override func numberOfSectionsInTableView(tableView: UITableView) -> Int { 
// #warning Incomplete implementation, return the number of sections 
return 1 
} 

override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int { 
// #warning Incomplete implementation, return the number of rows 
return username.count 
} 


override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell { 
let postCell = tableView.dequeueReusableCellWithIdentifier("Cell", forIndexPath: indexPath) as! TimelineTableViewCell 

imageFiles[indexPath.row].getDataInBackgroundWithBlock { (data, error) -> Void in 
if let downloadedImage = UIImage(data: data!) { 
postCell.postedImage.image = downloadedImage 

} 
} 

postCell.usernameLabel.text = username[indexPath.row] 
postCell.titleLabel.text = titles[indexPath.row] 

return postCell 
} 

}

Answer 1

你提到的 userId 指针的问题在这里：

let followedUser = object ["following"] as! String 
let query = PFQuery(className: "Post") 
query.whereKey("userId", equalTo: followedUser)

您提到Post 类的userId 列是一个User 指针，但是您将它作为带有followedUser 的字符串引用。

关于无法正常显示的图片，在您刷新 UI 之前它们不会显示。您正在使用正确的代码来加载数据

imageFiles[indexPath.row].getDataInBackgroundWithBlock { (data, error) -> Void in 
if let downloadedImage = UIImage(data: data!) { 
    postCell.postedImage.image = downloadedImage 
}

但是，问题在于，由于数据是异步加载，postCell 将在数据被提取之前返回到表中。缺少的关键部分是在完成处理程序中使用self.tableView.reloadData() 刷新表。

imageFiles[indexPath.row].getDataInBackgroundWithBlock { (data, error) -> Void in 
if let downloadedImage = UIImage(data: data!) { 
    postCell.postedImage.image = downloadedImage
    self.tableView.reloadData()
}

或者，我建议考虑使用来自ParseUI 框架的PFImageView。在完成查询时将每个PFFiles 分配给PFImageView，然后在每个PFImageView 上调用loadInBackground。一旦数据加载完毕，PFImageView 类会自动处理图像更新。