在swift中 - UITableview滾動時滾動

Question

我在tableview中列出了一個，動態加載數據和一個圖片 包含在單元格和一些文本中。當滾動被抽搐和 刺激用戶

任何想法，以提高表視圖的表現？

class MainViewController: UIViewController,UITableViewDataSource, UITableViewDelegate { 
    @IBOutlet weak var listTable: UITableView! 

    override func viewDidLoad() { 
     super.viewDidLoad() 

     self.listTable.delegate = self 
     self.listTable.dataSource = self 
     self.listTable.separatorStyle = .None 
     self.listTable.registerNib(UINib(nibName: "cellOne", bundle: nil), forCellReuseIdentifier: "cellOne") 
     self.listTable.registerNib(UINib(nibName: "cellTwo", bundle: nil), forCellReuseIdentifier: "cellTwo") 
     self.listTable.registerNib(UINib(nibName: "cellThree", bundle: nil), forCellReuseIdentifier: "cellThree") 
    } 

    func numberOfSectionsInTableView(tableView: UITableView) -> Int{ 
     return 1 
    } 

    func tableView(tableView: UITableView, heightForRowAtIndexPath indexPath: NSIndexPath) -> CGFloat { 
     if pageIndex == 7 { 
      return 120 
     } else if indexPath.row == 0 { 
      return 280 
     } else if (indexPath.row == 5 || indexPath.row == 4) { 
      return 200 
     } else if (indexPath.row == 8 || indexPath.row == 11) { 
      return 160 
     } 
     return 80 
    } 

    func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int{ 
     return 50 
    } 

    func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell { 
     let cell = UITableViewCell() 
     let listArray = self.listDataArray[indexPath.row] 

     if indexPath.row == 0 && pageIndex != 7 { 
      var cell = tableView.dequeueReusabl eCellWithIdentifier("cellOne") as! cellOne! 

      if cell == nil { 
       tableView.registerClass(cellOne.classForCoder(), forCellReuseIdentifier: "cellOne") 
       cell = cellOne(style: UITableViewCellStyle.Default, reuseIdentifier: "cellOne") 
      } 

      cell.headLbl.text = "\(listArray["title"]!)".html2String 
      cell.addImageView.userInteractionEnabled = true 
      let guster = UITapGestureRecognizer(target: self, action: "addTarget:") 
      cell.addImageView.addGestureRecognizer(guster) 
      cell.addImageView.tag = 1 

      let qualityOfServiceClass = QOS_CLASS_BACKGROUND 
      let backgroundQueue = dispatch_get_global_queue(qualityOfServiceClass, 0) 
      dispatch_async(backgroundQueue, { 
       if listArray["image"] != nil && self.imagesLocalDictionary[indexPath.row] == nil { 
        let u = listArray["image"] as! String 
        let url = NSURL(string: u) 
        if url != nil { 
         let data = NSData(contentsOfURL: url!) 

         if data != nil { 
          dispatch_async(dispatch_get_main_queue(), {() -> Void in 
           cell.imageViews.image = UIImage(data: data!) 
          }) 
          self.imagesLocalDictionary.setObject(data!, forKey: indexPath.row) 
         } 
        } 
       } else { 
        dispatch_async(dispatch_get_main_queue(), {() -> Void in 
         cell.imageViews.image = UIImage(data: self.imagesLocalDictionary[indexPath.row] as! NSData) 

        }) 
       } 
      }) 


      if Constants.sharedInstance.addData["1"] != nil { 
       cell.addImageView.image = UIImage(data: Constants.sharedInstance.addData["1"] as! NSData) 
      } 

      return cell 

     } else if indexPath.row == 4 && pageIndex != 7 { 
      var cell = tableView.dequeueReusableCellWithIdentifier("cellTwo") as! cellTwo! 

      if cell == nil { 
       tableView.registerClass(cellTwo.classForCoder(), forCellReuseIdentifier: "cellTwo") 
       cell = cellTwo(style: UITableViewCellStyle.Default, reuseIdentifier: "cellTwo") 
      } 

      cell.headLbl.text = "\(listArray["title"]!)".html2String 
      cell.addImageView.userInteractionEnabled = true 
      let guster = UITapGestureRecognizer(target: self, action: "addTarget:") 
      cell.addImageView.addGestureRecognizer(guster) 
      cell.addImageView.tag = 2 

      let qualityOfServiceClass = QOS_CLASS_BACKGROUND 
      let backgroundQueue = dispatch_get_global_queue(qualityOfServiceClass, 0) 
      dispatch_async(backgroundQueue, { 
       if listArray["image"] != nil && self.imagesLocalDictionary[indexPath.row] == nil { 
        let u = listArray["image"] as! String 
        let url = NSURL(string: u) 
        if url != nil { 
         let data = NSData(contentsOfURL: url!) 

         if data != nil { 
          dispatch_async(dispatch_get_main_queue(), {() -> Void in 
           cell.imageViews.image = UIImage(data: data!) 
          }) 
          self.imagesLocalDictionary.setObject(data!, forKey: indexPath.row) 
         } 

        } 
       } else { 
        dispatch_async(dispatch_get_main_queue(), {() -> Void in 
         cell.imageViews.image = UIImage(data: self.imagesLocalDictionary[indexPath.row] as! NSData) 
        }) 
       } 
      }) 

      if Constants.sharedInstance.addData["2"] != nil { 
       cell.addImageView.image = UIImage(data: Constants.sharedInstance.addData["2"] as! NSData) 
      } 

      return cell 

     } else if indexPath.row == 5 && pageIndex != 7 { 
      var cell = tableView.dequeueReusableCellWithIdentifier("cellThree") as! cellThree! 

      if cell == nil { 
       tableView.registerClass(cellThree.classForCoder(), forCellReuseIdentifier: "cellThree") 
       cell = cellThree(style: UITableViewCellStyle.Default, reuseIdentifier: "cellThree") 
      } 

      cell.headLbl.text = "\(listArray["title"]!)".html2String 
      cell.addImageView.userInteractionEnabled = true 
      let guster = UITapGestureRecognizer(target: self, action: "addTarget:") 
      cell.addImageView.addGestureRecognizer(guster) 
      cell.addImageView.tag = 3 

      let qualityOfServiceClass = QOS_CLASS_BACKGROUND 
      let backgroundQueue = dispatch_get_global_queue(qualityOfServiceClass, 0) 

      dispatch_async(backgroundQueue, { 
       if listArray["image"] != nil && self.imagesLocalDictionary[indexPath.row] == nil { 
        let u = listArray["image"] as! String 
        let url = NSURL(string: u) 
        if url != nil { 
         let data = NSData(contentsOfURL: url!) 

         if data != nil { 
          dispatch_async(dispatch_get_main_queue(), {() -> Void in 
           cell.imageViews.image = UIImage(data: data!) 
          }) 
          self.imagesLocalDictionary.setObject(data!, forKey: indexPath.row) 
         } 
        } 
       } else { 
        dispatch_async(dispatch_get_main_queue(), {() -> Void in 
         cell.imageViews.image = UIImage(data: self.imagesLocalDictionary[indexPath.row] as! NSData) 
        }) 
       } 
      }) 

      if Constants.sharedInstance.addData["3"] != nil { 
       cell.addImageView.image = UIImage(data: Constants.sharedInstance.addData["3"] as! NSData) 
      } 

      return cell 
     } else { 
      cell.backgroundColor = UIColor.groupTableViewBackgroundColor() 

      let container = UIView() 
      container.frame = CGRectMake(2, 1, tableView.frame.width-4, 78) 
      container.backgroundColor = UIColor.whiteColor() 
      cell.addSubview(container) 

      let headerLbl = UILabel() 
      headerLbl.backgroundColor = UIColor.clearColor() 

      headerLbl.frame = CGRectMake(120, 1, self.view.frame.width-130, 76) 
      headerLbl.numberOfLines = 0 
      headerLbl.font = UIFont(name: "TelegramHead", size: 18) 

      headerLbl.text = "\(listArray["title"]!)".html2String 
      headerLbl.lineBreakMode = NSLineBreakMode.ByCharWrapping 

      let imageView = UIImageView() 
      imageView.frame = CGRectMake(5, 5, 100, 68) 
      imageView.image = UIImage(named: "place_holder.jpg") 
      imageView.contentMode = UIViewContentMode.ScaleAspectFill 
      imageView.clipsToBounds = true 

      let blackLayerView = UIView(); 
      blackLayerView.frame = CGRectMake(0, 0, 0, 0); 
      blackLayerView.backgroundColor = UIColor.blackColor(); 
      blackLayerView.alpha = 0.4; 

      container.addSubview(imageView) 
      container.addSubview(blackLayerView); 
      container.addSubview(headerLbl) 

      if pageIndex == 7 { 
       container.frame = CGRectMake(2, 1, tableView.frame.width-4, 118) 
       imageView.frame = CGRectMake(5, 5, container.frame.width-10, 108) 
       blackLayerView.frame = imageView.frame; 
       headerLbl.frame = imageView.frame//CGRectMake(10, 5, self.view.frame.width-20, 100) 
       headerLbl.textColor = UIColor.whiteColor() 
       headerLbl.backgroundColor = UIColor.blackColor().colorWithAlphaComponent(0.2) 

      } else if (indexPath.row == 8 || indexPath.row == 11) && pageIndex != 7 { 
       let add = UIImageView() 
       add.frame = CGRectMake(2, 82, tableView.frame.width-4, 76) 
       //add.contentMode = UIViewContentMode.ScaleAspectFit; 
       cell.addSubview(add) 
       add.userInteractionEnabled = true 
       let guster = UITapGestureRecognizer(target: self, action: "addTarget:") 
       add.addGestureRecognizer(guster) 

       if Constants.sharedInstance.addData["4"] != nil && indexPath.row == 8{ 
        add.image = UIImage(data: Constants.sharedInstance.addData["4"] as! NSData) 
        add.tag = 4 
       } 

       if Constants.sharedInstance.addData["5"] != nil && indexPath.row == 11{ 
        add.image = UIImage(data: Constants.sharedInstance.addData["5"] as! NSData) 
        add.tag = 5 
       } 
      } 

      let qualityOfServiceClass = QOS_CLASS_BACKGROUND 
      let backgroundQueue = dispatch_get_global_queue(qualityOfServiceClass, 0) 

      dispatch_async(backgroundQueue, { 
       if listArray["image"] != nil && self.imagesLocalDictionary[indexPath.row] == nil { 
        let u = listArray["image"] as! String 
        let url = NSURL(string: u) 
        if url != nil { 
         let data = NSData(contentsOfURL: url!) 


         if data != nil { 
          dispatch_async(dispatch_get_main_queue(), {() -> Void in 
           imageView.image = UIImage(data: data!) 
           self.imagesLocalDictionary.setObject(data!, forKey: indexPath.row) 
          }) 
         } 
        } 

       } else { 
        dispatch_async(dispatch_get_main_queue(), {() -> Void in 
         imageView.image = UIImage(data: self.imagesLocalDictionary[indexPath.row] as! NSData) 
        }) 
       } 
      }) 
     } 
     return cell 
    } 
} 

我得到所需的功能。但在TableView中一個非常不自然的混蛋這會導致糟糕的用戶體驗。

Answer 1

有許多改進，你可以對這個代碼以提高性能。

1. 不註冊細胞cellForRow
2. 定義特定的自定義類爲每個小區在viewDidLoad中
3. 減少cellForRowAt
4. 使用的邏輯在創建cellForRowAt開始註冊他們的重用一個細胞的新實例，以後如果沒有其他情況下，比賽的子視圖添加到它。這個單元沒有重用。始終重用。您將使用更少的資源

我已經構建了一個複雜的表視圖，並創建了用於配置和返回特定indexPath的可重用單元格的函數。

class LargeImageCell: UITableViewCell { 
    var imageView: UIImageView() 

    // in init, init the cell, add imageview as subview, setup constraints 

    func setContent(imageURL: URL) { 
     // load image from cache or fetch from network in background 
    } 
} 

// in tableview/view controller 
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell { 
    switch indexPath.row { 
    case 0: 
     return self.getLargeImageCell(indexPath: indexPath) 
    // all other cases 
    } 
} 

這只是大概我是如何實現我的，只是儘量減少電池邏輯的數量，我已經alwayss發現最好創建自定義的細胞，而不是cellForRowAt加入他們，讓細胞配置本身

func getLargeImageCell(indexPath: NSIndexPath) -> UITableViewCell { 
    let data = self.data[indexPath.row] // model from db 

    var cell: UITableViewCell 
    if let c = self.tableView.dequeueReusableCellWithIdentifier("largeImageCell") as? LargeImageCell { 
     cell = c 
    } else { 
     cell = LargeImageCell(style: UITableViewCellStyle.Default, reuseIdentifier: "largeImageCell") 
    } 
    cell.setContent(imageURL: data.imageURL) 
    return cell 
}