麻煩可重複使用的細胞和陣列

Question

我的鬧鐘應用。用戶可以添加警報。如果我添加了過多的報警和向下滾動我會看到

如果我試圖用UISwitch（僅BUTTOM細胞），我會崩潰的應用程序，並得到錯誤：

Terminating app due to uncaught exception 'NSRangeException', reason: '*** -[__NSArrayI objectAtIndex:]: index 8 beyond bounds [0 .. 7]' 

我認爲數組裏面的問題。如何解決它？

import UIKit 

class MainAlarmViewController: UITableViewController{ 

    var alarmDelegate: AlarmApplicationDelegate = AppDelegate() 
    var alarmScheduler: AlarmSchedulerDelegate = Scheduler() 
    var alarmModel: Alarms = Alarms() 

    override func viewDidLoad() { 
     super.viewDidLoad() 
     tableView.allowsSelectionDuringEditing = true 
    } 

    override func viewWillAppear(_ animated: Bool) { 
     super.viewWillAppear(animated) 

     alarmModel = Alarms() 
     tableView.reloadData() 
     //dynamically append the edit button 
     if alarmModel.count != 0 { 
      self.navigationItem.leftBarButtonItem = editButtonItem 
     } 
     else { 
      self.navigationItem.leftBarButtonItem = nil 
     } 
     //unschedule all the notifications, faster than calling the cancelAllNotifications func 
     //UIApplication.shared.scheduledLocalNotifications = nil 

     let cells = tableView.visibleCells 
     if !cells.isEmpty { 
      for i in 0..<cells.count { 
       if alarmModel.alarms[i].enabled { 
        (cells[i].accessoryView as! UISwitch).setOn(true, animated: false) 
        cells[i].backgroundColor = UIColor.white 
        cells[i].textLabel?.alpha = 1.0 
        cells[i].detailTextLabel?.alpha = 1.0 
       } 
       else { 
        (cells[i].accessoryView as! UISwitch).setOn(false, animated: false) 
        cells[i].backgroundColor = UIColor.groupTableViewBackground 
        cells[i].textLabel?.alpha = 0.5 
        cells[i].detailTextLabel?.alpha = 0.5 
       } 
      } 
     } 
    } 

    override func didReceiveMemoryWarning() { 
     super.didReceiveMemoryWarning() 
    } 

    // MARK: - Table view data source 

    override func tableView(_ tableView: UITableView, heightForRowAt indexPath: IndexPath) -> CGFloat { 
     return 90 
    } 

    override func numberOfSections(in tableView: UITableView) -> Int { 
     // Return the number of sections. 
     return 1 
    } 

    override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int { 
     // Return the number of rows in the section. 
     if alarmModel.count == 0 { 
      tableView.separatorStyle = UITableViewCellSeparatorStyle.none 
     } 
     else { 
      tableView.separatorStyle = UITableViewCellSeparatorStyle.singleLine 
     } 
     return alarmModel.count 
    } 


    override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) { 
     if isEditing { 
      performSegue(withIdentifier: Id.editSegueIdentifier, sender: SegueInfo(curCellIndex: indexPath.row, isEditMode: true, label: alarmModel.alarms[indexPath.row].label, mediaLabel: alarmModel.alarms[indexPath.row].mediaLabel, mediaID: alarmModel.alarms[indexPath.row].mediaID, repeatWeekdays: alarmModel.alarms[indexPath.row].repeatWeekdays, enabled: alarmModel.alarms[indexPath.row].enabled, dateTime: alarmModel.alarms[indexPath.row].date)) 
     } 
    } 

    override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell { 
     var cell = tableView.dequeueReusableCell(withIdentifier: Id.alarmCellIdentifier) 
     if (cell == nil) { 
      cell = UITableViewCell(style: UITableViewCellStyle.subtitle, reuseIdentifier: Id.alarmCellIdentifier) 
     } 

     //cell text 
     cell!.selectionStyle = .none 
     cell!.tag = indexPath.row 
     let alarm: Alarm = alarmModel.alarms[indexPath.row] 
     let amAttr: [String : Any] = [NSFontAttributeName : UIFont.systemFont(ofSize: 20.0)] 
     let str = NSMutableAttributedString(string: alarm.formattedTime, attributes: amAttr) 
     let timeAttr: [String : Any] = [NSFontAttributeName : UIFont.systemFont(ofSize: 45.0)] 
     str.addAttributes(timeAttr, range: NSMakeRange(0, str.length-2)) 
     cell!.textLabel?.attributedText = str 
     cell!.detailTextLabel?.text = alarm.label 
     //append switch button 
     let sw = UISwitch(frame: CGRect()) 
     sw.transform = CGAffineTransform(scaleX: 0.9, y: 0.9); 

     //tag is used to indicate which row had been touched 
     sw.tag = indexPath.row 
     sw.addTarget(self, action: #selector(MainAlarmViewController.switchTapped(_:)), for: UIControlEvents.touchUpInside) 
     if alarm.enabled { 
      sw.setOn(true, animated: false) 
     } 
     cell!.accessoryView = sw 

     //delete empty seperator line 
     tableView.tableFooterView = UIView(frame: CGRect.zero) 

     return cell! 
    } 

    @IBAction func switchTapped(_ sender: UISwitch) { 
     let index = sender.tag 
     alarmModel.alarms[index].enabled = sender.isOn 
     if sender.isOn { 
      print("switch on") 
      sender.superview?.backgroundColor = UIColor.white 
      alarmScheduler.setNotificationWithDate(alarmModel.alarms[index].date, onWeekdaysForNotify: alarmModel.alarms[index].repeatWeekdays, snoozeEnabled: alarmModel.alarms[index].snoozeEnabled, onSnooze: false, soundName: alarmModel.alarms[index].mediaLabel, index: index) 
      let cells = tableView.visibleCells 
      if !cells.isEmpty { 
       cells[index].textLabel?.alpha = 1.0 
       cells[index].detailTextLabel?.alpha = 1.0 
      } 
     } 
     else { 
      print("switch off") 
      sender.superview?.backgroundColor = UIColor.groupTableViewBackground 
      let cells = tableView.visibleCells 
      if !cells.isEmpty { 
       cells[index].textLabel?.alpha = 0.5 
       cells[index].detailTextLabel?.alpha = 0.5 
      } 
      alarmScheduler.reSchedule() 
     } 
    } 


    // Override to support editing the table view. 
    override func tableView(_ tableView: UITableView, commit editingStyle: UITableViewCellEditingStyle, forRowAt indexPath: IndexPath) { 
     if editingStyle == .delete { 
      let index = indexPath.row 
      alarmModel.alarms.remove(at: index) 
      let cells = tableView.visibleCells 
      for cell in cells { 
       let sw = cell.accessoryView as! UISwitch 
       //adjust saved index when row deleted 
       if sw.tag > index { 
        sw.tag -= 1 
       } 
      } 
      if alarmModel.count == 0 { 
       self.navigationItem.leftBarButtonItem = nil 
      } 

      // Delete the row from the data source 
      tableView.deleteRows(at: [indexPath], with: .fade) 
      alarmScheduler.reSchedule() 
     } 
    } 

    // In a storyboard-based application, you will often want to do a little preparation before navigation 
    override func prepare(for segue: UIStoryboardSegue, sender: Any?) { 
     // Get the new view controller using segue.destinationViewController. 
     // Pass the selected object to the new view controller. 
     let dist = segue.destination as! UINavigationController 
     let addEditController = dist.topViewController as! AlarmAddEditViewController 
     if segue.identifier == Id.addSegueIdentifier { 
      addEditController.navigationItem.title = "Add Alarm" 
      addEditController.segueInfo = SegueInfo(curCellIndex: alarmModel.count, isEditMode: false, label: "Alarm", mediaLabel: "bell", mediaID: "", repeatWeekdays: [], enabled: false, dateTime: Date()) 
     } 
     else if segue.identifier == Id.editSegueIdentifier { 
      addEditController.navigationItem.title = "Edit Alarm" 
      addEditController.segueInfo = sender as! SegueInfo 
     } 
    } 

    @IBAction func unwindFromAddEditAlarmView(_ segue: UIStoryboardSegue) { 
     isEditing = false 
    } 

} 

Answer 1

當你得到一個運行時錯誤，你應該包括引發錯誤你的問題的一部分就行了。

標籤是一個相當脆弱的方法來找出什麼單元被挖掘。 （標籤是一種非常脆弱的方式來做任何事情。幾乎總是有一種更好的方式來查找視圖或找出關於視圖的信息，而不是使用標籤。）

我創建了一個UITableView的簡單擴展，讓你可以查詢表視圖用於單元格中任何視圖的IndexPath。寫一個按鈕IBAction很容易，該按鈕使用擴展名來確定哪個單元被點擊。我建議重做代碼中使用這種方法

擴展：

public extension UITableView { 

    /** 
    This method returns the indexPath of the cell that contains the specified view 
    - Parameter view: The view to find. 
    - Returns: The indexPath of the cell containing the view, or nil if it can't be found 
    */ 

    func indexPathForView(_ view: UIView) -> IndexPath? { 
    let origin = view.bounds.origin 
    let viewOrigin = self.convert(origin, from: view) 
    let indexPath = self.indexPathForRow(at: viewOrigin) 
    return indexPath 
    } 
} 

而且使用它的IBAction爲：

@IBAction func buttonTapped(_ button: UIButton) { 
    if let indexPath = self.tableView.indexPathForView(button) { 
    print("Button tapped at indexPath \(indexPath)") 
    } 
    else { 
    print("Button indexPath not found") 
    } 
} 

整個工程可在Github上：

TableViewExtension project on GitHub

我不知道蘋果爲什麼不將indexPathForView函數構建成UITableView。這似乎是一個普遍有用的功能。