Am make a tableview listing, data loading dynamically and a image contain in cell and some text. When it scroll gets jerking and irritating the users
有任何提高表格 View 性能的想法吗？
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
}
}
我确实获得了所需的功能。但是 TableView 上有一个非常不自然的抖动，这会导致糟糕的用户体验。
最佳答案
您可以对此代码进行许多改进以提高性能。
- 不要在 cellForRow 中注册单元格
- 为每个单元格定义特定的自定义类并注册它们以便在 viewDidLoad 中重用
- 减少 cellForRowAt 中使用的逻辑
- 在 cellForRowAt 的开头，您创建一个单元格的新实例，然后如果没有其他情况匹配，则向其中添加 subview 。该单元无法重复使用。始终重复使用。您将使用更少的资源
我之前已经构建了一个复杂的 TableView ，并创建了为特定索引路径配置和返回可重用单元格的函数。
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
}
}
这大致就是我的实现方式，只是尝试减少单元格中的逻辑量，我总是发现最好创建自定义单元格，而不是将它们添加到 cellForRowAt 中，让单元格自行配置
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
}
关于ios - 快速 - UITableview 在滚动时变得不稳定，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/43365848/