Question

class NewsTableViewController: UITableViewController {

@IBOutlet weak var authenticationButton: UIBarButtonItem!
var blogPosts = []

override func viewDidLoad() {
    super.viewDidLoad()

    // Uncomment the following line to preserve selection between presentations
    // self.clearsSelectionOnViewWillAppear = false

    // Uncomment the following line to display an Edit button in the navigation bar for this view controller.
    // self.navigationItem.rightBarButtonItem = self.editButtonItem()

    self.navigationItem.title = PFConfig.currentConfig().objectForKey("title") as? String

    authenticationButton.enabled = true
    if let authEnabled:Bool = PFConfig.currentConfig().objectForKey("adminEnabled") as? Bool {
        if authEnabled {
            authenticationButton.tintColor = UIView.appearance().tintColor
        } else {
            authenticationButton.tintColor = UIColor.darkGrayColor()
        }
    }

    loadPosts()

    //set the title
    PFConfig.getConfigInBackgroundWithBlock { (var config: PFConfig!, var error: NSError!) -> Void in

        if error == nil {

            if let title:String = config.objectForKey("title") as? String {
                self.navigationItem.title = title
            }

            if let authEnabled:Bool = config.objectForKey("adminEnabled") as? Bool {
                if authEnabled {
                    self.authenticationButton.tintColor = UIView.appearance().tintColor
                } else {
                    self.authenticationButton.tintColor = UIColor.darkGrayColor()
                }
            }   
        }   
    }   
}
// MARK: - Table view data source

override func numberOfSectionsInTableView(tableView: UITableView) -> Int {
    // #warning Potentially incomplete method implementation.
    // Return the number of sections.
    return 0
}

override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    // #warning Incomplete method implementation.
    // Return the number of rows in the section.

    return blogPosts.count
}

@IBAction func authenticate(sender: UIBarButtonItem) {

    //check if enabled, and if not, get error message from config

    if sender.tintColor != UIColor.darkGrayColor() {
        //enabled 
        var authAlert = UIAlertController(title: "Authenticate", message: "Please login to access the admin page.", preferredStyle: UIAlertControllerStyle.Alert)
        authAlert.addTextFieldWithConfigurationHandler({(textField: UITextField!) in
            textField.placeholder = "Password"
        })
        authAlert.addAction(UIAlertAction(title: "Cancel", style: UIAlertActionStyle.Cancel, handler: nil))
        authAlert.addAction(UIAlertAction(title: "Go", style: UIAlertActionStyle.Default, handler: { (goAction) -> Void in
            let textField:UITextField = authAlert.textFields![0] as UITextField
            let text = textField.text
            self.authenticateUser(text)
        }))

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


    } else {
        //disabled
        var serverMessage = PFConfig.currentConfig().objectForKey("adminEnabledMessage") as? String
        var errorMessage = UIAlertController(title: "Error", message: "The Admin Console is not enabled right now. Message from server: \(serverMessage!)", preferredStyle: UIAlertControllerStyle.Alert)
        errorMessage.addAction(UIAlertAction(title: "Dismiss", style: UIAlertActionStyle.Default, handler: nil))
        self.presentViewController(errorMessage, animated: true, completion: nil)

    }  
}

//authHandlers
func authenticateUser(password: String) {

    //get the server password
    let serverPass = PFConfig.currentConfig().objectForKey("password") as? String

    if password == serverPass {
        //move them to the admin console
        self.performSegueWithIdentifier("showConsole", sender: nil)   
    } else {
        //error message
        var errorMessage = UIAlertController(title: "Error", message: "Incorrect password, please try again.", preferredStyle: UIAlertControllerStyle.Alert)
        errorMessage.addAction(UIAlertAction(title: "Dismiss", style: UIAlertActionStyle.Default, handler: nil))
        self.presentViewController(errorMessage, animated: true, completion: nil)

    }   
}

func loadPosts() {
    let query = PFQuery(className: "Posts")
    query.findObjectsInBackgroundWithBlock { (objects, error: NSError!) -> Void in
        if error == nil {
            self.blogPosts = objects
            self.tableView.reloadData()
        } else {
            var errorMessage = UIAlertController(title: "Error", message: "There was an error retrieving the posts. Please try again later. \(error.localizedDescription)", preferredStyle: UIAlertControllerStyle.Alert)
            errorMessage.addAction(UIAlertAction(title: "Dismiss", style: UIAlertActionStyle.Default, handler: nil))
            self.presentViewController(errorMessage, animated: true, completion: nil)   
        }
    }     
}

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

    // Configure the cell...
    let currentPost:PFObject = blogPosts.objectAtIndex(indexPath.row) as PFObject
    let title = currentPost.objectForKey("title") as String
    cell.titleLabelC.text = title

    let gmtFormatter:NSDateFormatter = NSDateFormatter()
    gmtFormatter.dateFormat = "E MMM d @ hh:mm a"
    let dateString = gmtFormatter.stringFromDate(currentPost.createdAt)

    cell.detailsLabelC.text = dateString

    return cell
}

这是我添加到故事板的UITableView的代码。出于某种原因，当我在loadPosts（）中调用self.tableView.reloadData（）时，它不会更新表，也不会调用cellForRowAtIndexPath。知道为什么吗？

Answer 1

您的TableViewDataSource总是为部分数返回0，但您至少需要1.只需删除该DataSource函数，因为它默认为1。

Answer 2

有关多线程的此错误。 UITableView - 它是UI元素。 UI仅适用于主线程。这意味着reloadData也只能在main thred中运行。在您的代码query.findObjectsInBackgroundWithBlock中是异步方法。因此reloadData在此方法中不起作用。你应该通过GCD在主线程中调用它。

dispatch_async(dispatch_get_main_queue(), {
     self.tableView.reloadData()
})

self.tableview.reloaddata（）没有在swift中调用

2 个答案: