我正在开发一个消息传递应用程序，我想显示消息内容下发送消息的位置。我尝试通过将用户的位置数据发送到Firebase，然后尝试检索数据以将其显示为字符串来完成此操作。
获取用户位置正常（我使用CoreLocation这样做）和将数据上传到Firebase实时数据库一样。我将位置与每条消息一起保存：
让itemRef = messageRef.childByAutoId（）// 1 让messageItem = [// 2 “文字”：文字， “senderId”：senderId， “location”：getLocation（） ] itemRef.setValue（messageItem）// 3
然后尝试以另一种方法检索数据：
override func collectionView(collectionView: JSQMessagesCollectionView!, attributedTextForCellBottomLabelAtIndexPath indexPath: NSIndexPath!) -> NSAttributedString! {
var locationId: String = ""
let messagesQuery = messageRef
let message = messages[indexPath.item]
messagesQuery.observeEventType(.ChildAdded) { (snapshot: FIRDataSnapshot!) in
locationId = snapshot.value!["location"] as! String
print(locationId)
}
if message.senderId == senderId {
return nil
} else {
return NSAttributedString(string: locationId)
}
}
正确的位置会打印到控制台，但我的应用中没有显示任何内容。但是，如果我将变量locationId替换为任何其他字符串，它就可以工作。
我认为我的问题在于Firebase检索。
如果有人可以帮我解决这个问题，那将非常感激。
以下是我的类的其余代码供参考（以防万一）：
类ChatViewController：JSQMessagesViewController，CLLocationManagerDelegate {
// MARK: Properties
//Firebase
var rootRef = FIRDatabase.database().reference()
var messageRef: FIRDatabaseReference!
var locationRef: FIRDatabaseReference!
//JSQMessages
var messages = [JSQMessage]()
var outgoingBubbleImageView: JSQMessagesBubbleImage!
var incomingBubbleImageView: JSQMessagesBubbleImage!
var purp = UIColor.init(red:47/255, green: 53/255, blue: 144/255, alpha: 1)
var roastish = UIColor.init(red: 255/255, green: 35/255, blue: 35/255, alpha: 1.0)
var orangish = UIColor.init(red: 231/255, green: 83/255, blue: 55/255, alpha: 1.0)
var gray = UIColor.init(red: 241/255, green: 251/255, blue: 241/255, alpha: 1)
//Location
var city: String = ""
var state: String = ""
var country: String = ""
var locationManager = CLLocationManager()
func getLocation() -> String {
if city == ("") && state == ("") && country == (""){
return "Planet Earth"
}
else {
if country == ("United States") {
return self.city + ", " + self.state
}
else {
return self.city + ", " + self.state + ", " + self.country
}
}
}
override func viewDidLoad() {
super.viewDidLoad()
// Initialize location
locationManager.delegate = self
locationManager.requestWhenInUseAuthorization()
if CLLocationManager.locationServicesEnabled() {
//collect user's location
locationManager.desiredAccuracy = kCLLocationAccuracyThreeKilometers
locationManager.requestLocation()
locationManager.startUpdatingLocation()
}
// Change the navigation bar background color
navigationController!.navigationBar.barTintColor = gray
self.navigationController!.navigationBar.titleTextAttributes = [ NSFontAttributeName: UIFont(name: "Avenir Next", size: 20)!]
title = "RoastChat"
setupBubbles()
// No avatars
// Remove file upload icon
self.inputToolbar.contentView.leftBarButtonItem = nil;
// Send button
self.inputToolbar.contentView.rightBarButtonItem.setTitle("Roast", forState: UIControlState.Normal)
// Send button color
self.inputToolbar.contentView.rightBarButtonItem.setTitleColor(roastish, forState: UIControlState.Normal)
// Input bar text placeholder
self.inputToolbar.contentView.textView.placeHolder = "RoastChat"
collectionView!.collectionViewLayout.incomingAvatarViewSize = CGSizeZero
collectionView!.collectionViewLayout.outgoingAvatarViewSize = CGSizeZero
//Firebase reference
messageRef = rootRef.child("messages")
locationRef = rootRef.child("locations")
}
override func viewDidAppear(animated: Bool) {
super.viewDidAppear(animated)
observeMessages()
}
override func viewDidDisappear(animated: Bool) {
super.viewDidDisappear(animated)
}
func locationManager(manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
//--- CLGeocode to get address of current location ---//
CLGeocoder().reverseGeocodeLocation(manager.location!, completionHandler: {(placemarks, error)->Void in
if let pm = placemarks?.first
{
self.displayLocationInfo(pm)
}
})
}
func displayLocationInfo(placemark: CLPlacemark?)
{
if let containsPlacemark = placemark
{
//stop updating location
locationManager.stopUpdatingLocation()
self.city = (containsPlacemark.locality != nil) ? containsPlacemark.locality! : ""
self.state = (containsPlacemark.administrativeArea != nil) ? containsPlacemark.administrativeArea! : ""
self.country = (containsPlacemark.country != nil) ? containsPlacemark.country! : ""
}
}
func locationManager(manager: CLLocationManager, didFailWithError error: NSError) {
print("Error while updating location " + error.localizedDescription)
}
override func collectionView(collectionView: JSQMessagesCollectionView!,
messageDataForItemAtIndexPath indexPath: NSIndexPath!) -> JSQMessageData! {
return messages[indexPath.item]
}
override func collectionView(collectionView: JSQMessagesCollectionView!,
messageBubbleImageDataForItemAtIndexPath indexPath: NSIndexPath!) -> JSQMessageBubbleImageDataSource! {
let message = messages[indexPath.item] // 1
if message.senderId == senderId { // 2
return outgoingBubbleImageView
} else { // 3
return incomingBubbleImageView
}
}
override func collectionView(collectionView: UICollectionView,
numberOfItemsInSection section: Int) -> Int {
return messages.count
}
override func collectionView(collectionView: JSQMessagesCollectionView!,
avatarImageDataForItemAtIndexPath indexPath: NSIndexPath!) -> JSQMessageAvatarImageDataSource! {
return nil
}
private func setupBubbles() {
let factory = JSQMessagesBubbleImageFactory()
outgoingBubbleImageView = factory.outgoingMessagesBubbleImageWithColor(
UIColor.jsq_messageBubbleBlueColor())
incomingBubbleImageView = factory.incomingMessagesBubbleImageWithColor(
roastish)
}
func addMessage(id: String, text: String) {
let message = JSQMessage(senderId: id, displayName: "", text: text)
messages.append(message)
}
override func collectionView(collectionView: UICollectionView,
cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
let cell = super.collectionView(collectionView, cellForItemAtIndexPath: indexPath)
as! JSQMessagesCollectionViewCell
let message = messages[indexPath.item]
if message.senderId == senderId {
cell.textView!.textColor = UIColor.whiteColor()
} else {
cell.textView!.textColor = UIColor.whiteColor()
}
return cell
}
override func didPressSendButton(button: UIButton!, withMessageText text: String!, senderId: String!,
senderDisplayName: String!, date: NSDate!) {
let itemRef = messageRef.childByAutoId() // 1
let messageItem = [ // 2
"text": text,
"senderId": senderId,
"location": getLocation()
]
itemRef.setValue(messageItem) // 3
// 4
JSQSystemSoundPlayer.jsq_playMessageSentSound()
// 5
finishSendingMessage()
Answers.logCustomEventWithName("Message sent", customAttributes: nil)
}
private func observeMessages() {
// 1
let messagesQuery = messageRef.queryLimitedToLast(25)
// 2
messagesQuery.observeEventType(.ChildAdded) { (snapshot: FIRDataSnapshot!) in
// 3
let id = snapshot.value!["senderId"] as! String
let text = snapshot.value!["text"] as! String
// 4
self.addMessage(id, text: text)
// 5
self.finishReceivingMessage()
Answers.logCustomEventWithName("Visited RoastChat", customAttributes: nil)
}
}
override func collectionView(collectionView: JSQMessagesCollectionView!, attributedTextForCellBottomLabelAtIndexPath indexPath: NSIndexPath!) -> NSAttributedString! {
var locationId: String = ""
let messagesQuery = messageRef
let message = messages[indexPath.item]
messagesQuery.observeEventType(.ChildAdded) { (snapshot: FIRDataSnapshot!) in
locationId = snapshot.value!["location"] as! String
print(locationId)
}
if message.senderId == senderId {
return nil
} else {
return NSAttributedString(string: locationId)
}
}
override func collectionView(collectionView: JSQMessagesCollectionView, layout collectionViewLayout: JSQMessagesCollectionViewFlowLayout, heightForCellBottomLabelAtIndexPath indexPath: NSIndexPath) -> CGFloat {
return kJSQMessagesCollectionViewCellLabelHeightDefault
}
override func collectionView(collectionView: JSQMessagesCollectionView!, didTapMessageBubbleAtIndexPath indexPath: NSIndexPath!) {
super.collectionView(collectionView, didTapMessageBubbleAtIndexPath: indexPath)
let data = self.messages[indexPath.row]
print("They tapped: " + (data.text))
}
}
答案 0 :(得分：2)
99％的时间从互联网上检索某些数据 - 就像这里的情况一样，您观察Firebase事件以获取由其他用户发送的位置 - 代码以异步方式工作。
这意味着在检索位置时触发的闭包是独立于referencedTextForCellBottomLabelAtIndexPath函数的其余部分调用的。
因此，当您实际获得该位置时，该函数已经返回了使用空locationId创建的NSAttributedString;为什么空？因为你已经将它的初始值设置为＆＃34;＆＃34;。 调用messagesQuery.observeEventType在本地捕获locationId属性时传递闭包，因此您可以将其设置为从API检索的内容并且打印工作正常。但是在流程到达闭包代码的末尾之后，这个值就会从内存中消失并且无处可用。
要使您的应用有效，您需要做的是在获得locationId后更新单元格底部标签 。你可以用几种不同的方式去做。我会建议两个类似的。
最简单，最直接的方法是，如果单元格能够在Firebase事件中观察并更新自身。
func collectionView(collectionView: UICollectionView, willDisplayCell cell: UICollectionViewCell, forItemAtIndexPath indexPath: NSIndexPath) {
let cell = collectionView.dequeueReusableCellWithReuseIdentifier(YourCellClass.identifier, forIndexPath: indexPath) as! YourCellClass
cell.messagesQuery = messagesRef
return cell
}
在你的手机代码中你会有类似的东西：
class YourCellClass: UICollectionViewCell {
static let identifier = String(YourCellClass)
var messagesQuery: FIRDatabaseReference {
didSet {
messagesQuery.observeEventType(.ChildAdded) { [weak self] snapshot in
guard let `self` = self, value = snapshot.value as? [String: AnyObject], locationId = value["location"] as? String else { return }
dispatch_async(dispatch_get_main_queue()) {
self.bottomLabel.attributedText = NSAttributedText(string: locationId)
}
}
}
}
// all your other cell code goes here
}
另一个更好的选择是使用MVVM，并且单元格的视图模型将负责获取位置，单元格将在其上观察视图模型并更新自身，但我认为现在对你来说有点太多了;）
P.S。请记住，我编写了这个顶级代码，因此我无法100％保证它会立即编译。
答案 1 :(得分：0)
我无法以任何其他方式进行检索。相反，我利用JSQMessagesViewControllers其他内置方法来解决我的问题。该框架有一个名为senderDisplayName的内置变量。由于我正在制作的这个应用程序的性质是匿名的，我不需要使用它，所以我操纵senderDisplay名称来显示用户的位置。
func addMessage(id: String, text: String, displayName: String) {
let message = JSQMessage(senderId: id, displayName: displayName, text: text)
messages.append(message)
}
然后我将displayName设置为位置：
private func observeMessages() {
// 1
let messagesQuery = messageRef.queryLimitedToLast(25)
// 2
messagesQuery.observeEventType(.ChildAdded) { (snapshot: FIRDataSnapshot!) in
// 3
let id = snapshot.value!["senderId"] as! String
let text = snapshot.value!["text"] as! String
let locationId = snapshot.value!["location"] as! String
// 4
// self.addMessage(id, text: locationId.lowercaseString + ": \n" + text)
self.addMessage(id, text: text, displayName: locationId)
// 5
self.finishReceivingMessage()
Answers.logCustomEventWithName("Visited RoastChat", customAttributes: nil)
}
}
然后我只使用内置的attributedTextForCellBottomLabelAtIndexPath将我的底部标签设置为用户的位置：
override func collectionView(collectionView: JSQMessagesCollectionView!, attributedTextForCellBottomLabelAtIndexPath indexPath: NSIndexPath!) -> NSAttributedString! {
let message = messages[indexPath.item]
if message.senderId == senderId {
return nil
} else {
return NSAttributedString(string: message.senderDisplayName)
}
}
它完美无缺！这就是编程的全部内容，解决问题。
感谢所有帮助过我并指出正确方向的人。