我正在创建一个简单的聊天应用程序，它有一个加载屏幕，如果用户未登录，则该屏幕会转到登录屏幕，如果用户登录，则直接转到他的聊天。聊天显示在UICollectionView. 当我第一次测试时，我用我在类本身中声明的虚拟数据填充它，并且一切正常。现在，我从加载屏幕中的在线数据库中获取用户的聊天记录，并将它们存储在一个名为的数组中，该数组被user_chats全局声明。
我使用以下代码填充UICollectionView：
func collectionView(collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
// getUserChats()
return user_chats.count
}
func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCellWithReuseIdentifier("chat_cell" , forIndexPath: indexPath) as! SingleChat
cell.chatName?.text = user_chats[indexPath.row].chat_partner!.name
cell.chatTextPreview?.text = user_chats[indexPath.row].chat_messages!.last!.text
let profile_pic_URL = NSURL(string : user_chats[indexPath.row].chat_partner!.profile_pic!)
downloadImage(profile_pic_URL!, imageView: cell.chatProfilePic)
cell.chatProfilePic.layer.cornerRadius = 26.5
cell.chatProfilePic.layer.masksToBounds = true
let dividerLineView: UIView = {
let view = UIView()
view.backgroundColor = UIColor(white: 0.5, alpha: 0.5)
return view
}()
dividerLineView.translatesAutoresizingMaskIntoConstraints = false
cell.addSubview(dividerLineView)
cell.addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("H:|-1-[v0]|", options: NSLayoutFormatOptions(), metrics: nil, views: ["v0": dividerLineView]))
cell.addSubview(dividerLineView)
cell.addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("V:[v0(1)]|", options: NSLayoutFormatOptions(), metrics: nil, views: ["v0": dividerLineView]))
return cell
}
func collectionView(collectionView: UICollectionView, didSelectItemAtIndexPath indexPath: NSIndexPath) {
self.performSegueWithIdentifier("showChat", sender: self)
}
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if (segue.identifier == "showChat") {
let IndexPaths = self.collectionView!.indexPathsForSelectedItems()!
let IndexPath = IndexPaths[0] as NSIndexPath
let vc = segue.destinationViewController as! SingleChatFull
vc.title = user_chats[IndexPath.row].chat_partner!.name
}
}
数据获取：
func getUserChats() {
let scriptUrl = "*****"
let userID = self.defaults.stringForKey("userId")
let params = "user_id=" + userID!
let myUrl = NSURL(string: scriptUrl);
let request: NSMutableURLRequest = NSMutableURLRequest(URL: myUrl!)
request.HTTPMethod = "POST"
let data = params.dataUsingEncoding(NSUTF8StringEncoding)
request.timeoutInterval = 10
request.HTTPBody=data
request.HTTPShouldHandleCookies=false
UIApplication.sharedApplication().networkActivityIndicatorVisible = true
let queue:NSOperationQueue = NSOperationQueue()
NSURLConnection.sendAsynchronousRequest(request, queue: queue, completionHandler:{ (response: NSURLResponse?, data: NSData?, error: NSError?) -> Void in
do {
if (data != nil) {
do {
var dataString = String(data: data!, encoding: NSUTF8StringEncoding)
var delimiter = "]"
var token = dataString!.componentsSeparatedByString(delimiter)
dataString = token[0] + "]"
print(dataString)
let data_fixed = dataString!.dataUsingEncoding(NSUTF8StringEncoding)
do {
let jsonArray = try NSJSONSerialization.JSONObjectWithData(data_fixed!, options:[])
// LOOP THROUGH JSON ARRAY AND FETCH VALUES
for anItem in jsonArray as! [Dictionary<String, AnyObject>] {
let curr_chat = Chat()
if let chatId = anItem["chatId"] as? String {
curr_chat.id = chatId
}
let friend = Friend()
let user1id = anItem["user1_id"] as! String
let user2id = anItem["user2_id"] as! String
if (user1id == userID) {
if let user2id = anItem["user2_id"] as? String {
friend.id = user2id
}
if let user2name = anItem["user2_name"] as? String {
friend.name = user2name
}
if let user2profilepic = anItem["user2_profile_pic"] as? String {
friend.profile_pic = user2profilepic
}
}
else if (user2id == userID){
if let user1id = anItem["user1_id"] as? String {
friend.id = user1id
}
if let user1name = anItem["user1_name"] as? String {
friend.name = user1name
}
if let user1profilepic = anItem["user1_profile_pic"] as? String {
friend.profile_pic = user1profilepic
}
}
curr_chat.chat_partner = friend
var chat_messages = [Message]()
if let dataArray = anItem["message"] as? [String : AnyObject] {
for (_, messageDictionary) in dataArray {
if let onemessage = messageDictionary as? [String : AnyObject] { let curr_message = Message()
if let messageid = onemessage["message_id"] as? String {
curr_message.id = messageid
}
if let messagedate = onemessage["timestamp"] as? String {
let dateFormatter = NSDateFormatter()
dateFormatter.dateFormat = "yyyy-MM-dd HH:mm:ss"
let date = dateFormatter.dateFromString(messagedate)
curr_message.date = date
}
if let messagesender = onemessage["sender"] as? String {
curr_message.sender = messagesender
}
if let messagetext = onemessage["text"] as? String {
curr_message.text = messagetext
}
chat_messages.append(curr_message)
}}
}
curr_chat.chat_messages = chat_messages
user_chats.append(curr_chat)
}
}
catch {
print("Error: \(error)")
}
}
// NSUserDefaults.standardUserDefaults().setObject(user_chats, forKey: "userChats")
}
else {
dispatch_async(dispatch_get_main_queue(), {
let uiAlert = UIAlertController(title: "No Internet Connection", message: "Please check your internet connection.", preferredStyle: UIAlertControllerStyle.Alert)
uiAlert.addAction(UIAlertAction(title: "Ok", style: .Default, handler: { action in
self.dismissViewControllerAnimated(true, completion:nil)
}))
self.presentViewController(uiAlert, animated: true, completion: nil)
})
}
} catch _ {
NSLog("error")
}
})
}
问题是集合视图现在总是空的。我做了一些调试并在第一个函数中放置了一个断点，我看到当加载屏幕仍然显示给用户并且聊天屏幕还没有加载时调用了这个方法。我怀疑这是在加载屏幕中从互联网获取数据之前调用的，因此user_chats数组的大小为 0。我习惯于使用 Android，并且ListView在ListView父视图之前永远不会填充显示在屏幕上，因此我感到困惑。从在线数据库中获取数据的方法工作正常，因为我已经对其进行了广泛的调试，所以问题不存在。