ios - 使用异步数据更新 TableViewCell

Question

我有一个 tableViewCell，总共包含 8 个图像，分为两个 block (每个 block 4 个图像)。这些图像会异步下载并存储到数组中，然后在 tableViewCell 的 cellForRowAtIndexPath 中使用来填充图像。当一个 block 的所有图像都已添加到字典 (groupTOImages) 的数组中时，我重新加载 tableView。按照我的方式，我得到的结果与数据加载不一致。有些图像被加载到不该加载的位置。有没有办法下载图像并在 tableViewCell 中获得一致的结果。

var groupNames = [NSManagedObject]()
var groupTOPeople = [NSManagedObject: [String]]()
var groupTOImages = [NSManagedObject: [UIImage]]()
func getGroups() {
     ...
     for group in groupNames {
            groupTOImages[group] = []
            if let people = groupTOPeople[group] {
                var mycount = 0
            for peeps in people {
                InstagramEngine.sharedEngine().getUserDetails(peeps, withSuccess: { user in
                    if let ppic = user.profilePictureURL {
                        let picUrl = ppic.absoluteString
                        print(picUrl)
                        ImageLoader.sharedLoader.imageForUrl(picUrl) { (image, url) -> () in
                            self.groupTOImages[group]?.append(image!)
                            mycount++
                            if mycount == people.count {
                                self.tableView.reloadData()

                            }
                        }
                    } else {
                        self.groupTOImages[group]?.append(UIImage())
                        mycount++
                        if mycount == people.count {
                            self.tableView.reloadData()
                        }
                    }


                    }, failure: nil )
            }
        }

        }

var counter = 0
var groupCount = 0
var groupCounter = 0
override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
        let cellInfo = GroupCellsArray[indexPath.section]
     ...
     case .userGroups:
            let cell = tableView.dequeueReusableCellWithIdentifier(cellInfo.description, forIndexPath: indexPath) as! GroupTableViewCell
            if groupNames.count > 0 {
                var gp = groupNames[groupCounter]
                switch counter {
                    case 0:
                        cell.firstTitle.text = (gp.valueForKey("name") as! String)
                        if let ourImages = groupTOImages[gp] {
                        for image in ourImages {
                            print(image.description)
                            print("groupCount \(groupCounter)")
                            cell.firstUserButtons[groupCount].layer.borderWidth = 0
                            cell.firstUserButtons[groupCount].setImage(image, forState: .Normal)
                            groupCount++
                            if groupCount == ourImages.count {
                                groupCount = 0
                                counter++
                                groupCounter++
                                gp = groupNames[groupCounter]
                            }
                        }
                    }
                    case 1:
                    if let title = gp.valueForKey("name") as? String {
                        cell.secondTitle.text = title
                        if let ourImages = groupTOImages[gp] {
                            for image in ourImages {
                                cell.secondUserButtons[groupCount].layer.borderWidth = 0
                                cell.secondUserButtons[groupCount].setImage(image, forState: .Normal)
                                groupCount++
                                if groupCount == ourImages.count {
                                    groupCount = 0
                                    counter = 0
                                    groupCounter++
                                    gp = groupNames[groupCounter]
                                }
                            }

                        }
                    } else {
                        cell.secondTitle.text = "Title"
                    }
                default:
                    break
                }

每一行如下图所示:

在 cellForRowAtIndexPath 中使用 ImageLoader 的代码:

var counter = 0
        for group in groupNames {
            print("in the second")
            groupTOImages[group] = []
            if let people = groupTOPeople[group] {
                var mycount = 0
            for peeps in people {
                InstagramEngine.sharedEngine().getUserDetails(peeps, withSuccess: { user in
                    if let ppic = user.profilePictureURL {
                        let picUrl = ppic.absoluteString
                        self.groupTOImages[group]?.append(picUrl)
                        counter++
                        mycount++
                        if counter == self.groupNames.count && mycount == people.count
                        {
                            dispatch_async(dispatch_get_main_queue()) {
                                self.tableView.reloadData()
                            }
                        }
                    } else {
                        self.groupTOImages[group]?.append(nil)
                        counter++
                        mycount++
                        if counter == self.groupNames.count && mycount == people.count
                        {
                            dispatch_async(dispatch_get_main_queue()) {
                                self.tableView.reloadData()
                            }
                        }
                    }

                }, failure: nil )
            }
        }


 if groupNames.count > 0 {
                var gp = groupNames[groupCounter]
                print("counter!!!!")
                print("groupCount \(counter)")
                switch counter {
                    case 0:
                        if let ourImages = groupTOImages[gp] {
                            cell.firstTitle.text = (gp.valueForKey("name") as! String)
                            print(cell.firstTitle.text)
                            for image in ourImages {
                                if let url = image {
                                    print("I get in here")
                                    ImageLoader.sharedLoader.imageForUrl(url) { (image, url) -> () in
                                    cell.firstUserButtons[self.groupCount].layer.borderWidth = 0
                                    cell.firstUserButtons[self.groupCount].setImage(image, forState: .Normal)
                                        self.groupCount++
                                        if self.groupCount == ourImages.count {
                                            self.groupCount = 0
                                            self.counter++
                                            self.groupCounter++
                                            gp = self.groupNames[self.groupCounter]
                                        }
                                    }

                                } else {
                                    self.groupCount++
                                    if self.groupCount == ourImages.count {
                                        self.groupCount = 0
                                        self.counter++
                                        self.groupCounter++
                                        gp = self.groupNames[self.groupCounter]
                                    }
                                }
                            }
                        }
                case 1:
                    if let title = gp.valueForKey("name") as? String {
                        cell.secondTitle.text = title
                        if let ourImages = groupTOImages[gp] {
                            for image in ourImages {
                                if let url = image {
                                    ImageLoader.sharedLoader.imageForUrl(url) { (image, url) -> () in
                                    cell.secondUserButtons[self.groupCount].layer.borderWidth = 0
                                    cell.secondUserButtons[self.groupCount].setImage(image, forState: .Normal)
                                    self.groupCount++
                                        if self.groupCount == ourImages.count {
                                            self.groupCount = 0
                                            self.counter++
                                            self.groupCounter++
                                            gp = self.groupNames[self.groupCounter]
                                        }
                                    }
                                } else {
                                    self.groupCount++
                                    if self.groupCount == ourImages.count {
                                        self.groupCount = 0
                                        self.counter = 0
                                        self.groupCounter++
                                        gp = self.groupNames[self.groupCounter]
                                    }
                                }
                            }

                        }
                    } else {
                        cell.secondTitle.text = "Title"
                    }

Answer 1

您应该将 self.tableView.reloadData() 替换为

dispatch_async(dispatch_get_main_queue(), { () -> Void in 
    self.tableView.reloadData()
})

希望这有帮助!