[英]Dequeue Reusable Cell crashes when calling dequeued cell
我正在嘗試使用一個列出多個內容的表格視圖,並允許用戶瀏覽並選擇帶有復選框的多個單元格。 我的代碼可以工作到一定程度,問題是應用程序崩潰並出現以下錯誤
致命錯誤:展開一個可選值時意外發現nil
每當我調用以下代碼
swift let currentCell = recommendToFriendTableView.cellForRow(at: selectedRow[i]) as? RecommendToFriendsTableViewCell
這是我們設置單元的方法
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
if (tableView == self.friendListTableView) {
let cell: FriendListTableViewCell = tableView.dequeueReusableCell(withIdentifier: "FriendListCell") as! FriendListTableViewCell
let rowNumber = (indexPath as NSIndexPath).row
var name = ""
if searchActive {
name = filtered[rowNumber]
}
else {
name = names[rowNumber]
}
cell.friendNameLabel.text = name
cell.friendNameLabel.backgroundColor = tableViewBgColor
cell.friendNameLabel.textColor = textColor
cell.recommendToFriendButton.layer.borderWidth = 1
cell.recommendToFriendButton.layer.borderColor = tableViewBgColor.cgColor
cell.recommendToFriendButton.layer.cornerRadius = 6
cell.recommendToFriendButton.backgroundColor = buttonBgColor
cell.backgroundColor = tableViewBgColor
//set target for buttons
cell.recommendToFriendButton.tag = rowNumber
cell.recommendToFriendButton.addTarget(self, action:#selector(recommendToFriendButtonClicked), for: UIControl.Event.touchUpInside)
return cell
}
else {
let cell: RecommendToFriendsTableViewCell = tableView.dequeueReusableCell(withIdentifier: "RecommendToFriendsCell") as! RecommendToFriendsTableViewCell
let rowNumber = (indexPath as NSIndexPath).row
// set the content view background color
cell.contentView.backgroundColor = tableViewBgColor
// set the text color
cell.nameLabel.textColor = textColor
var dict_friend = NSMutableDictionary()
if searchActive {
dict_friend = filteredFriendsArray[rowNumber]
}
else {
dict_friend = friendsArray[rowNumber]
}
let name = dict_friend["name"] as! String
cell.nameLabel.text = name
let friendUID = dict_friend["uid"] as! String
cell.friendID = friendUID
let imageAddress = dict_friend["photo"] as? String
if imageAddress != "unavailable" && imageAddress != nil && imageAddress != ""{
//Swift forces us to wrap strings as optional to use them in logic
if let imageURL = imageAddress as String? {
//Swift forces us to wrap strings as optional to use them in logic
if let image = imageURL as String? {
//We convert the string into a URL and get the image
let url = URL(string: image)
URLSession.shared.dataTask(with: url!, completionHandler: { (data, response, error) in
if error != nil {
print(error!)
return
}
//We create a new async thread to download and update the image
DispatchQueue.main.async {
//imageView.image = UIImage(data: data!)
cell.photoImageView.image = UIImage(data:data!)
}
}).resume()
}
} else {
cell.photoImageView!.image = UIImage(named: "placeholder-profile-male.png")
}
} else {
cell.photoImageView!.image = UIImage(named: "placeholder-profile-male.png")
}
cell.checkBoxImageView.image = cell.checkBoxImageView.image!.withRenderingMode(.alwaysTemplate)
cell.checkBoxImageView.tintColor = textColor
// Style the profile photo to show in a circle
cell.photoImageView.layer.borderWidth = 0
cell.photoImageView.layer.borderColor = tableViewBgColor.cgColor
// Set cornerRadius = a square UIImageView frame size width / 2
// In our case, UIImageView height = width = 60 points
cell.photoImageView.layer.cornerRadius = 30
cell.photoImageView.clipsToBounds = true
cell.selectionStyle = .none // to prevent cells from being "highlighted"
return cell
}
}
這是我們與他們互動的方法。 崩潰發生在cellForRow調用中,導致看不見的單元格(也稱為已出隊)
var firstFriendName: String = ""
var numberOfFriends = 0
if let selectedRow = recommendToFriendTableView.indexPathsForSelectedRows {
numberOfFriends = selectedRow.count
for i in 0..<selectedRow.count {
let currentCell = recommendToFriendTableView.cellForRow(at: selectedRow[i]) as! RecommendToFriendsTableViewCell
let friendID = currentCell.friendID
idList.append(",\(friendID)")
}
let firstSelectedCell = recommendToFriendTableView.cellForRow(at: selectedRow[0]) as! RecommendToFriendsTableViewCell
firstFriendName = firstSelectedCell.nameLabel.text!
經過大約一天的實驗,我還沒有弄清楚實際的問題(除了觀察到的似乎是關於調用出隊單元格的觀察)
任何幫助表示贊賞。
當這條線
let currentCell = recommendToFriendTableView.cellForRow(at: selectedRow[i]) as! RecommendToFriendsTableViewCell
崩潰意味着您訪問的是非可見單元,因此無論使用
if let currentCell = recommendToFriendTableView.cellForRow(at: selectedRow[i]) as? RecommendToFriendsTableViewCell { }
或更好地使用表的dataSource數組從單元格中獲取要錯誤地處理的數據
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