I have a comparatively large dataset (about 1,000 rows) that need to be filled into the UITableView from Firebase. I am also using sections and search functionality in the UITableView.
This is how it looks at the moment with the required functionality:
As you can see, section functionality has been used in UITableView. But the issue that I face currently is extremely slow loading of data. I have localPersistenceEnabled but it still takes about 3-4 seconds to populate all data and the experience is less than pleasant.
How do I fix this? I read about Pagination but I also want to preserve the functionality of sections. For sections, this is the code I'm using:
override func viewWillAppear(_ animated: Bool) {
self.racks.removeAll()
self.sectionals.removeAll()
self.tableView.reloadData()
ref.queryOrdered(byChild: "chamber").observe(.childAdded, with: { (snapshot) -> Void in
// Manage TableView Sections & Rows for Rack Additions
var doesSectionExist = false
let segment = (snapshot.value as! [String : AnyObject])["segment"] as! String
if self.sectionals.contains(segment){
// There's already an index present for this letter.
doesSectionExist = true
var snapshotData = self.racks[segment]
snapshotData?.append(snapshot)
self.racks[segment] = snapshotData
}
else{
self.racks[segment] = [snapshot]
self.sectionals.append(segment)
}
self.allRacks.append(snapshot)
self.sectionals = self.sectionals.sorted()
if !doesSectionExist{
self.tableView.insertSections(IndexSet(integer: self.sectionals.index(of: segment)!), with: .fade)
}
else{
//let rowCount = self.customers[firstChar]?.count
self.tableView.reloadSections(IndexSet(integer: self.sectionals.index(of: segment)!), with: .fade)
//self.tableView.insertRowsAtIndexPaths([NSIndexPath(forRow: rowCount!-1, inSection: self.sectionals.indexOf(firstChar)!)], withRowAnimation: .Fade)
}
})
}
override func numberOfSections(in tableView: UITableView) -> Int {
if searchController.isActive && searchController.searchBar.text != "" {
return 1
}
else{
return sectionals.count
}
}
override func tableView(_ tableView: UITableView, titleForHeaderInSection section: Int) -> String? {
if searchController.isActive && searchController.searchBar.text != "" {
return "Top Matches"
}
else{
return sectionals[section]
}
}
override func sectionIndexTitles(for tableView: UITableView) -> [String]? {
if searchController.isActive && searchController.searchBar.text != "" {
return nil
}
else{
return sectionals
}
}
So the idea is to provide section index titles for quick access and improve loading time to load such a large dataset.
Thank you.
Related
I have a tableview which has 2 sections. Both of the sections have UISearchBar in the indexPath.row 0 and the rest of the rows in each section populate the list of array.
Whenever I type some text in search bar every time the searchBar(_ searchBar: UISearchBar, textDidChange searchText: String) delegate method gets called and inside the delegate method I call tableView.reloadData() to reload the search results in tableview.
Now the problem is each time the tableView reloads the UISearchBar reloads too (as UISearchbar is in row number 1) and every time the SearchBar keypad Resigns.
Instead of doing tableView.reloadData() I even tried to reload every row except the first one using bellow code
let allButFirst = (self.tableView.indexPathsForVisibleRows ?? []).filter { $0.section != selectedSection || $0.row != 0 }
self.tableView.reloadRows(at: allButFirst, with: .automatic)
But no luck. App gets crashed saying
Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'attempt to insert row 2 into section 0, but there are only 2 rows in section 0 after the update'
You are probably changing the data source and then you are reloading rows at index paths what doesn't exist yet.
It is not so easy, but let's have an example: Before you start typing, the search result will contain something like this:
["aa", "ab", "ba", "bb"]
Then you will type "a" to the search bar and data source changes into:
["aa", "ab"]
tableView.deleteRows(at: [IndexPath(row:3, section: 0), IndexPath(row:4, section: 0)], with: .automatic)
then you delete everything in this searchbar and your data source will change to the default: ["aa", "ab", "ba", "bb"]
so in this case you need to call:
tableView.insertRows(at: [IndexPath(row:3, section: 0), IndexPath(row:4, section: 0)], with: .automatic)
I created some working example - without storyboard source, I believe it is pretty simple to recreated it according this class.
class SearchCell: UITableViewCell {
#IBOutlet weak var textField:UITextField?
}
class TextCell: UITableViewCell {
#IBOutlet weak var label:UILabel?
}
class ViewController: UIViewController, UITableViewDataSource, UITextFieldDelegate {
#IBOutlet weak var tableView: UITableView?
weak var firstSectionTextField: UITextField?
var originalDataSource:[[String]] = [["aa","ab","ba","bb"], ["aa","ab","ba","bb"]]
var dataSource:[[String]] = []
let skipRowWithSearchInput = 1
override func viewDidLoad() {
super.viewDidLoad()
dataSource = originalDataSource
tableView?.tableFooterView = UIView()
tableView?.tableHeaderView = UIView()
}
func numberOfSections(in tableView: UITableView) -> Int {
return dataSource.count
}
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return dataSource[section].count + skipRowWithSearchInput
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
if indexPath.row == 0, let cell = tableView.dequeueReusableCell(withIdentifier: "search", for: indexPath) as? SearchCell {
cell.textField?.removeTarget(self, action: #selector(textFieldDidChangeText(sender:)), for: .editingChanged)
cell.textField?.addTarget(self, action: #selector(textFieldDidChangeText(sender:)), for: .editingChanged)
if indexPath.section == 0 {
firstSectionTextField = cell.textField
}
return cell
} else if let cell = tableView.dequeueReusableCell(withIdentifier: "text", for: indexPath) as? TextCell {
cell.label?.text = dataSource[indexPath.section][indexPath.row - skipRowWithSearchInput]
return cell
} else {
return UITableViewCell()
}
}
#objc func textFieldDidChangeText(sender: UITextField) {
let section = sender == firstSectionTextField ? 0 : 1
let text = sender.text ?? ""
let oldDataSource:[String] = dataSource[section]
//if the search bar is empty then use the original data source to display all results, or initial one
let newDataSource:[String] = text.count == 0 ? originalDataSource[section] : originalDataSource[section].filter({$0.contains(text)})
var insertedRows:[IndexPath] = []
var deletedRows:[IndexPath] = []
var movedRows:[(from:IndexPath,to:IndexPath)] = []
//resolve inserted rows
newDataSource.enumerated().forEach { (tuple) in let (toIndex, element) = tuple
if oldDataSource.contains(element) == false {
insertedRows.append(IndexPath(row: toIndex + skipRowWithSearchInput, section: section))
}
}
//resolve deleted rows
oldDataSource.enumerated().forEach { (tuple) in let (fromIndex, element) = tuple
if newDataSource.contains(element) == false {
deletedRows.append(IndexPath(row: fromIndex + skipRowWithSearchInput, section: section))
}
}
//resolve moved rows
oldDataSource.enumerated().forEach { (tuple) in let (index, element) = tuple
if newDataSource.count > index, let offset = newDataSource.firstIndex(where: {element == $0}), index != offset {
movedRows.append((from: IndexPath(row: index + skipRowWithSearchInput, section: section), to: IndexPath(row: offset + skipRowWithSearchInput, section: section)))
}
}
//now set dataSource for uitableview, right before you are doing the changes
dataSource[section] = newDataSource
tableView?.beginUpdates()
if insertedRows.count > 0 {
tableView?.insertRows(at: insertedRows, with: .automatic)
}
if deletedRows.count > 0 {
tableView?.deleteRows(at: deletedRows, with: .automatic)
}
movedRows.forEach({
tableView?.moveRow(at: $0.from, to: $0.to)
})
tableView?.endUpdates()
}
}
the result:
If do you need to clarify something, feel free to ask in comment.
Try this-
tableView.beginUpdates()
//Do the update thing
tableView.endUpdates()
It worked.
I took two sections one for search field and another for reloading data (rows populating data).
I took separate custom cell for search and took outlet in that class itself.
and in viewForHeaderInSection I used tableView.dequeueReusableCell(withIdentifier:) and returned customCell.contentView
Then I called tableview.ReloadData() in searchBar(_ searchBar: UISearchBar, textDidChange searchText: String)
It worked without problem.
I create a table view that every time I scroll to the end of table it will show shimmer in table section 1 for waiting the api load a new data. After api finish load data, new data will append to the array that use for contain all data that be show to table view on section 0, then reload the table view to update the section 1 numberOfRowsInSection to 0 to hide the shimmer and update the section 0 numberOfRowsInSection
So this is the example of my code
fileprivate var data = [dataArray]() {
didSet {
guard !data.isEmpty else {
return
}
tableView.reloadData()
tableView.layoutIfNeeded()
view.layoutIfNeeded()
}
}
fileprivate var isLoadingMore: Bool = false {
didSet {
tableView.reloadSections(IndexSet(integer: 1), with: .automatic)
tableView.layoutIfNeeded()
tableViewHeightConstraint.constant = tableView.contentSize.height + 60.0
view.layoutIfNeeded()
}
}
fileprivate func loadData() {
if let size = self.paging.totalSize,
data.count >= size {
return
}
let limit = paging.limit
let offset = paging.offset
guard !isLoadingMore else { return }
isLoadingMore = true
controller.requestContent(
completion: { [weak self] (success, offset, size, data) in
DispatchQueue.main.async {
self?.isLoadingMore = false
guard let list = data,
let data = list as? [dataArray],
let size = size else {
return
}
if success {
if self?.paging.currentPage == 0 {
self?.data = data
if self?.scrollView.frame.size.height >= self?.scrollView.contentSize.height {
self?.paging.totalSize = size
self?.paging.currentPage += 1
self?.loadData()
return
}
} else {
self?.data.append(contentsOf: songs)
}
self?.paging.totalSize = size
self?.paging.currentPage += 1
} else {
self?.alert("failed")
}
}
})
}
fileprivate func loadDataFromCoreData() {
isLoadingMore = false
let context = (UIApplication.shared.delegate as! AppDelegate).managedObjectContext
let dataFromCoreData = Datas.fetchData(context: context).filter({$0.isSaved})
songs = dataFromCoreData.map({ dataArray(song: $0) })
}
func numberOfSections(in tableView: UITableView) -> Int {
return 2
}
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
switch section {
case 0:
return data.count
case 1:
return isLoadingMore ? 1 : 0
default:
return 0
}
}
func scrollViewDidEndDragging(_ scrollView: UIScrollView, willDecelerate decelerate: Bool) {
if ((scrollView.contentOffset.y + scrollView.frame.size.height) >= scrollView.contentSize.height){
loadData()
}
}
func setupForCeckingAvailableData() {
utility.checkInternetAccess = { [weak self] result in
if result {
self?.paging = Paging()
self?.loadData()
} else {
self?.loadDataFromCoreData()
}
}
}
override func viewDidLoad() {
super.viewDidLoad()
setupForCeckingAvailableData()
}
so some time when I first time load or try fetch new data by scrolling to the end of table I got a crash with the message is
Invalid update: invalid number of rows in section 0. The number of rows contained in an existing section after the update (0) must be equal to the number of rows contained in that section before the update (10), plus or minus the number of rows inserted or deleted from that section (0 inserted, 0 deleted) and plus or minus the number of rows moved into or out of that section (0 moved in, 0 moved out).
So what the cause of it? Why got that crash even though I already use reloadData() every time I append a new data to variable data. Should I change reloadData() to
tableView.beginUpdates()
tableView.insertRows(at: indexPaths, with: .automatic)
tableView.endUpdates()
? if that so, is that the crash cause insertRows only refresh specific row and section so no take a loot of time to refresh table with a loot of datas??
That's all of my question, Thank you
I just want to point out something else.
Generally speaking, Singletons are Evil and I avoid them like the plague.
This is a real big code smell and would advise you to stop using this type of code:
TableView.beginUpdates()
TableView.insertRows(at: indexPaths, with: .automatic)
TableView.endUpdates()
See What is so bad about singletons? there are many more blog posts about it.
after I do some research I found a clue.
I add tableView.reloadData() before tableView.reloadSections(IndexSet(integer: 1), with: .automatic) because when I see the crashlytic crash happend at tableView.reloadSections(IndexSet(integer: 1), with: .automatic)
Sorry, I'm beginner to learn IOS.
I have a problem about my tableView and reload data.
When I frequently call "getData", I will crash and get error.
But I don't know where my data make it crash.
I guess I first call reloadData, and then the list.count are already changed in global thread
Have any advice to avoid it?
Thanks.
Crash Log:
fatal error: Index out of range
Model:
class ChatroomList:Model {
var all:[Chatroom] {
var rooms:[Chatroom] = [Chatroom]()
self.chatrooms.forEach({ (id,chatroom) in
if showType.contains(chatroom.type) {
rooms.append(chatroom)
}
})
return rooms
}
}
ViewController:
import RxCocoa
import RxSwift
import Alamofire
class ListViewController: UIViewController, UITableViewDataSource, UITableViewDelegate {
let chatrooms:ChatroomList = ChatroomList()
var list:[Chatroom] = [Chatroom]()
var subscribe:Disposable?
override func viewDidLoad() {
super.viewDidLoad()
self.tableView.dataSource = self
self.tableView.delegate = self
}
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
subscribe = rooms.notifySubject.subscribe({ json in
self.getData() //here is called frequently
})
self.getData()
}
override func viewWillDisappear(_ animated: Bool) {
super.viewWillDisappear(animated)
subscribe?.dispose()
}
func getData() {
var idList:[String] = []
self.list.removeAll()
self.list = chatrooms.all
guard self.list.isEmpty == false else {
return
}
DispatchQueue.global().async() {
self.list.sort(by: { (a,b) in
if a.message.datetime.isEmpty {
return false
}
return a.message.datetime > b.message.datetime
})
self.list = self.list.filter { (chatroom) -> Bool in
if chatroom.id.isEmpty {
return true
}
if idList.contains(chatroom.id) {
return false
}
idList.append(chatroom.id)
return true
}
DispatchQueue.main.sync() {
self.tableView.reloadData()
}
}
}
}
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return list.count
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
if list[indexPath.row].type == .city {
let cell: ChatroomCityTableViewCell = ChatroomCityTableViewCell(style: .default, reuseIdentifier: nil)
cell.loadByCityChatroom(chatroom: list[indexPath.row], cityId: list[indexPath.row].cityId)
return cell
}else{
let cell: ChatroomTableViewCell = ChatroomTableViewCell(style: .default, reuseIdentifier: nil)
cell.loadByChatroom(chatroom: list[indexPath.row])
return cell
}
}
The problem is most likely caused by how you currently use the GCD (Grand central dispatch).
When reloading, the tableView will ask many different questions like the number of rows and the cells for each of these rows. If the data changes between one of these calls it will result in an inconsistency exception because it tried to add or remove a number of row that no longer represents the data.
Reloading the tableView asynchronously on the main thread while your getData function can change the list at any given time will result in the above error.
The solution is not simple, you need to rethink how to update the list so it won't change while the tableView reload its data.
One thing you could try is to do something like:
func getData() {
// You cannot clear or change self.list here
guard !chatrooms.all.isEmpty else { return }
DispatchQueue.global().async() {
let updatedData = process(newData: self.chatrooms.all)
DispatchQueue.main.sync() {
self.list = updatedData
self.tableView.reloadData()
}
}
}
private func process(newData data: [Chatroom]) -> [Chatroom] {
// Do all your logic without making any changes to self.list
}
The key is to never make any change to the data that is used when reloading the tableView except synchronously on the main thread juste before reloading.
I am trying to load some data from CloudKit to populate a tableview with custom cells and I am having difficulty getting the data to appear.
When I define the number of rows as the count of the CKRecord array the tableview shows up, but with nothing loaded into them. They are just spaced out correctly for the images to be in there. Also, when I set breakpoints at let record = matches[indexPath.row] it won't trigger.
However, if I change the return matches.count to an actual number, the project crashes at let record = matches[indexPath.row]
with the error that the index is out of range. I want to keep the number of rows as the count for the record array, but that is the only change that will actually execute the override function that calls the tableview cell.
override func numberOfSections(in tableView: UITableView) -> Int {
return 1
}
override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return matches.count
}
override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "Card", for: indexPath) as! MatchTableViewCell
let record = matches[indexPath.row]
if let img = record.value(forKey: "Picture") as? CKAsset {
cell.profileimg.image = UIImage(contentsOfFile: img.fileURL.path)
}
return cell
}
Any advice is appreciated
Update- here is where I load the model
func loadModel() {
let totalMatch = (defaults.object(forKey: "passedmatch") as! [String] )
let predicateMatch = NSPredicate(format: "not (UserID IN %#)", totalMatch )
ProfilesbyLocation = defaults.object(forKey: "Location") as! String
let query = CKQuery(recordType: ProfilesbyLocation , predicate: predicateMatch )
publicData.perform(query, inZoneWith: nil,completionHandler: ({results, error in
print("loading")
if (error != nil) {
let nsError = error! as NSError
print(nsError.localizedDescription)
print ("error")
} else {
if results!.count > 0 {
DispatchQueue.main.async() {
self.tableView.reloadData()
self.refresh.endRefreshing()
print("refreshed")
}
}
}
}
)
)}
It sounds like you are not calling
tableview.reloadData()
after your asynchronous data comes in. Leave numberOfRowsInSection as it is and make sure when your network request comes back you are reloading. That should do it.
If you received your data from background thread(or queue), please make sure when you update your UI elements under the main thread(or queue). Try this:
DispatchQueue.main.async {
tableView.reloadData()
}
This solved my problem.
First, disconnect the Delegate/DataSource of the TableView from the Interface Builder refer this image. When you have finally prepared your data that is matches array then add this.
`DispatchQueue.main.async {
tableView.dataSource = self
tableView.delegate = self
tableView.reloadData
}`
Hope this helps.
It looks like your matches is incorrect. Before you call func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int)
, you should check your matches.
If you are still not sure about that. You can init your matches with string literals and have a try.
I have success working tableview with json parsing code. But may have 1000 more item so I need pagination when scrolling bottom side. I don't know how can I do this for my code shown below. For objective-C, there are a lot of examples but for Swift I didn't find a working example.
import UIKit
class ViewController: UIViewController, UITableViewDataSource,UITableViewDelegate {
let kSuccessTitle = "Congratulations"
let kErrorTitle = "Connection error"
let kNoticeTitle = "Notice"
let kWarningTitle = "Warning"
let kInfoTitle = "Info"
let kSubtitle = "You've just displayed this awesome Pop Up View"
#IBOutlet weak var myTableView: UITableView!
#IBOutlet weak var myActivityIndicator: UIActivityIndicatorView!
var privateList = [String]()
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
}
override func viewWillAppear(animated: Bool) {
super.viewWillAppear(animated)
loadItems()
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
internal func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int
{
return privateList.count
}
internal func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell
{
let cell:myCell = tableView.dequeueReusableCellWithIdentifier("myCell") as! myCell
cell.titleLabel.text = privateList[indexPath.row]
return cell
}
func tableView(tableView: UITableView, commitEditingStyle editingStyle: UITableViewCellEditingStyle, forRowAtIndexPath indexPath: NSIndexPath) {
if (editingStyle == UITableViewCellEditingStyle.Delete){
print(indexPath.row)
let alert = SCLAlertView()
alert.addButton("Hayır"){ }
alert.addButton("Evet") {
self.myTableView.beginUpdates()
self.privateList.removeAtIndex(indexPath.row)
tableView.deleteRowsAtIndexPaths([indexPath], withRowAnimation: UITableViewRowAnimation.Left)
print("Silindi")
self.myTableView.endUpdates()
self.loadItems()
}
alert.showSuccess(kSuccessTitle, subTitle: kSubtitle)
}
}
func tableView(tableView: UITableView, canEditRowAtIndexPath indexPath: NSIndexPath) -> Bool {
// the cells you would like the actions to appear needs to be editable
return true
}
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if(segue.identifier == "Detail") {
let destinationView = segue.destinationViewController as! DetailViewController
if let indexPath = myTableView.indexPathForCell(sender as! UITableViewCell) {
destinationView.privateLista = privateList[indexPath.row]
}
}
}
internal func tableView(tableView: UITableView, estimatedHeightForHeaderInSection section: Int) -> CGFloat
{
return 0.0
}
func loadItems()
{
loadItemsNow("privateList")
}
func loadItemsNow(listType:String){
myActivityIndicator.startAnimating()
let listUrlString = "http://bla.com/json2.php?listType=" + listType + "&t=" + NSUUID().UUIDString
let myUrl = NSURL(string: listUrlString);
let request = NSMutableURLRequest(URL:myUrl!);
request.HTTPMethod = "GET";
let task = NSURLSession.sharedSession().dataTaskWithRequest(request) {
data, response, error in
if error != nil {
print(error!.localizedDescription)
dispatch_async(dispatch_get_main_queue(),{
self.myActivityIndicator.stopAnimating()
})
return
}
do {
let json = try NSJSONSerialization.JSONObjectWithData(data!, options: .MutableContainers) as? NSArray
if let parseJSON = json {
self.privateList = parseJSON as! [String]
}
} catch {
print(error)
}
dispatch_async(dispatch_get_main_queue(),{
self.myActivityIndicator.stopAnimating()
self.myTableView.reloadData()
})
}
task.resume()
}
}
For that you need to have server side change also.
Server will accept fromIndex and batchSize in the API url as query param.
let listUrlString = "http://bla.com/json2.php?listType=" + listType + "&t=" + NSUUID().UUIDString + "&batchSize=" + batchSize + "&fromIndex=" + fromIndex
In the server response, there will be an extra key totalItems. This will be used to identify all items are received or not. An array or items fromIndex to batchSize number of items.
In the app side
First loadItem() will be called with fromIndex = 0 and batchSize = 20 (for example in viewDidLoad() or viewWillAppear). removeAll items from privateList array before calling loadItem() for the first time
Server returns an array of first 20 items and totalItems total number of items in the server.
Append the 20 items in privateList array and reload tableView
In tableView:cellForRowAtIndexPath method check if the cell is the last cell. And check if totalItems (form server) is greater than privateList.count. That means there are more items in the server to load
if indexPath.row == privateList.count - 1 { // last cell
if totalItems > privateList.count { // more items to fetch
loadItem() // increment `fromIndex` by 20 before server call
}
}
Question: where is refresh ? will be scrolling ?
Refresh after appending new items in the array when server response received. (step 3)
Scrolling will trigger tableView:cellForRowAtIndexPath for every cell when user scrolls. Code is checking if it is the last cell and fetch remaining items. (step 4)
Sample project added: https://github.com/rishi420/TableViewPaging
SWIFT 3.0 and 4.0
If you're sending the page number in the API request then this is the ideal way for implementing pagination in your app.
declare the variable current Page with initial Value 0 and a bool to check if any list is being loaded with initial value false
var currentPage : Int = 0
var isLoadingList : Bool = false
This is the function that gets the list example:
func getListFromServer(_ pageNumber: Int){
self.isLoadingList = false
self.table.reloadData()
}
This is the function that increments page number and calls the API function
func loadMoreItemsForList(){
currentPage += 1
getListFromServer(currentPage)
}
this is the method that will be called when the scrollView scrolls
func scrollViewDidScroll(_ scrollView: UIScrollView) {
if (((scrollView.contentOffset.y + scrollView.frame.size.height) > scrollView.contentSize.height ) && !isLoadingList){
self.isLoadingList = true
self.loadMoreItemsForList()
}
}
P.S. the bool isLoadingList role is to prevent the scroll view from getting more lists in one drag to the bottom of the table view.
The good and efficient way to do it is by using scrollviewDelegate in tableview
Just add UIScrollViewDelegate in your viewController
In view controller
//For Pagination
var isDataLoading:Bool=false
var pageNo:Int=0
var limit:Int=20
var offset:Int=0 //pageNo*limit
var didEndReached:Bool=false
viewDidLoad(_){
tableview.delegate=self //To enable scrollviewdelegate
}
Override two methods from this delegate
func scrollViewWillBeginDragging(_ scrollView: UIScrollView) {
print("scrollViewWillBeginDragging")
isDataLoading = false
}
func scrollViewDidEndDecelerating(_ scrollView: UIScrollView) {
print("scrollViewDidEndDecelerating")
}
//Pagination
func scrollViewDidEndDragging(_ scrollView: UIScrollView, willDecelerate decelerate: Bool) {
print("scrollViewDidEndDragging")
if ((tableView.contentOffset.y + tableView.frame.size.height) >= tableView.contentSize.height)
{
if !isDataLoading{
isDataLoading = true
self.pageNo=self.pageNo+1
self.limit=self.limit+10
self.offset=self.limit * self.pageNo
loadCallLogData(offset: self.offset, limit: self.limit)
}
}
}
This is now a little bit easier with the addition of a new protocol in iOS10: UITableViewDataSourcePrefetching
https://developer.apple.com/documentation/uikit/uitableviewdatasourceprefetching
//It works fine
func getPageCount(TotalCount : Int) -> Int{
var num = TotalCount
let reminder = num % 50
print(reminder)
if reminder != 0{
num = TotalCount/50
num = num + 1
}else{
num = TotalCount/50
}
return num
}
func tableView(_ tableView: UITableView, willDisplay cell: UITableViewCell, forRowAt indexPath: IndexPath) {
let TotalPage = self.getPageCount(TotalCount: Int(Datacount)!)
let lastItem = self.mainArr.count - 1
if indexPath.row == lastItem {
print("IndexRow\(indexPath.row)")
if self.page < TotalPage-1 {
self.view_Loader.isHidden = false
self.view_LoaderHeight.constant = 50
self.page += 1
self.YourAPI()
}
}
}`
By using UITableViewDelegate, u can call the function
func tableView(_ tableView: UITableView, willDisplay cell: UITableViewCell, forRowAt indexPath: IndexPath) {
let lastItem = self.mes.count - 1
if indexPath.row == lastItem {
print("IndexRow\(indexPath.row)")
if currentPage < totalPage {
currentPage += 1
//Get data from Server
}
}
}
I needed something similar on a project and my solution was:
1 - create a variable numberOfObjectsInSubArray (initial value 30 or whatever you want)
2 - create a subarray to add a number of objects from your privateList array every time i tap "show more"
let subArray = privateList?.subarrayWithRange(NSMakeRange(0, numberOfObjectsInSubArray))
And use it on
internal func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int
{
return subArray.count
}
3- Whenever you need to show more objects, do:
func addMoreObjectsOnTableView () {
numberOfObjectsInSubArray += 30
if (numberOfObjectsInSubArray < privateList.count) {
subArray = privateList?.subarrayWithRange(NSMakeRange(0, numberOfObjectsInSubArray))
} else {
subArray = privateList?.subarrayWithRange(NSMakeRange(0, privateList.count))
}
tableView.reloadData()
}
I hope it helps
I've tried an approach with willDisplayCell. But it produces unwanted stops during scrolling which makes the user experience not good.
I think a better way is to do it in scrollViewDidEndDecelerating delegate method. It calls when the scroll finishes and only then new data comes. User sees that there is new content and scroll again if he wants. I've taken the answer here but instead of scrollViewDidEndDragging I use scrollViewDidEndDecelerating. It looks just better in my case. Here is some code from my project.
func scrollViewDidEndDecelerating(_ scrollView: UIScrollView) {
guard scrollView == tableView,
(scrollView.contentOffset.y + scrollView.frame.size.height) >= scrollView.contentSize.height,
!viewModel.isLastPeriodicsPage else { return }
viewModel.paginatePeriodics(tableView.getLastIndexPath())
}
Another way of doing this is: You may set a threshold for getting elements while sending request each time:
Lets say you you are fetching 20 elements first time. You will be saving last fetched record id or number for getting list of next 20 elements.
let lastFetchedIndex = 20;
I am assuming that you have already added these records in your myArray. MyArray is the dataSource of tableView. Now myArray is containing 40 objects. I am going to make a list of indexPaths of rows that needs to be inserted in tableView now.
var indexPathsArray = [NSIndexPath]()
for index in lastFetchedIndex..<myArray.count{
let indexPath = NSIndexPath(forRow: index, inSection: 0)
indexPathsArray.append(indexPath)
}
Here I am updating my tableView. Make sure your dataSource i mean your myArray has already been updated. So that it may insert rows properly.
self.tableView.beginUpdates()
tableView!.insertRowsAtIndexPaths(indexPathsArray, withRowAnimation: .Fade)
self.tableView.endUpdates()
Add another section to your tableview, let this section have only 1 row which will be a cell containing an activity indicator, to denote loading.
internal func numberOfSectionsInTableView(tableView: UITableView) -> Int
{
return 2;
}
internal func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int
{
if section == 0 {
return privateList.count
} else if section == 1 { // this is going to be the last section with just 1 cell which will show the loading indicator
return 1
}
}
internal func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell
{
if section == 0 {
let cell:myCell = tableView.dequeueReusableCellWithIdentifier("myCell") as! myCell
cell.titleLabel.text = privateList[indexPath.row]
return cell
} else if section == 1 {
//create the cell to show loading indicator
...
//here we call loadItems so that there is an indication that something is loading and once loaded we relaod the tableview
self.loadItems()
}
}
here is a sample code for collection view :
var page = 0
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell{
print("page Num:\(page)")
}
func collectionView(_ collectionView: UICollectionView, willDisplay cell: UICollectionViewCell, forItemAt indexPath: IndexPath){
if arrImagesData.count-1 == indexPath.row && arrImagesData.count%10 == 0{
getMoreImages(page)
}
}
func getMoreImages(page:Int){
//hit api
if api_success == true {
if self.page == 0 {
self.arrImagesData.removeAll()
}
self.arrImagesData.appendContentsOf(api_data)
self.collectionImages.reloadData()
self.page = self.page + 1
}
}
API handler is api handler for network call that just do POST and GET calls. getNotifications is basically just a post call with params( offset and pageSize ) and in response there is list.
Main logic is changing offset depending on cell in willDisplay collectionView delegate. Comment if you having any question , happy to help.
var isFetching: Bool = false
var offset = 0
var totalListOnServerCount = 20 // it must be returned from server
var pageSize = 10 // get 10 objects for instance
// MARK: - API Handler
private func fetchNotifications(){
// return from function if already fetching list
guard !isFetching else {return}
if offset == 0{
// empty list for first call i.e offset = 0
self.anyList.removeAll()
self.collectionView.reloadData()
}
isFetching = true
// API call to fetch notifications with given offset or page number depends on server logic just simple POST Call
APIHandler.shared.getNotifications(offset: offset) {[weak self] (response, error) in
if let response = response {
self?.isFetching = false
if self?.offset == 0{
// fetch response from server for first fetch
self?.notificationsResponse = response
if self?.refreshControl.isRefreshing ?? false {
self?.refreshControl.endRefreshing()
}
}else{
// append if already exist ( pagination )
self?.notificationsResponse?.notifications.append(contentsOf: response.notifications)
}
self?.collectionView.reloadData()
}
}
}
// MARK: - Collection View Delegate
func collectionView(_ collectionView: UICollectionView, willDisplay cell: UICollectionViewCell, forItemAt indexPath: IndexPath) {
guard let anyList = responseFromServer else { return }
// check if scroll reach last index available and keep fetching till our model list has all entries from server
if indexPath.item == anyList.count - 1 && anyList.count < totalListOnServerCount{
offset += pageSize
fetchNotifications()
}
}
Made a General purpouse pagination framework: 🎉
https://github.com/eonist/PaginationTable
let table = Table(rowData: [], frame: .zero, style: .plain)
view = table
table.isFetching = true
Table.fetchData(range: table.paginationRange) { rowItem in
DispatchQueue.main.async { [weak table] in
table?.rowData += rowItem
table?.reloadData()
table?.paginationIndex += Table.paginationAmount // set the new pagination index
table?.isFetching = false
}
}
Swift 5 (Full comprehensive pagination solution)
The UI code:
https://github.com/eonist/PaginationTable
The Data Model code:
https://github.com/eonist/PaginationService
Core components:
rowData: This array will grow on each scroll-ended-event until it has loaded all items from backend-API
paginationAmount: The amount to fetch on each pagination cycle
paginationIndex: The current amount of cells (this grows as you load more data
isFetching: A boolean that lets the code know if data is already loading or not, to avoid double fetching etc
fetchData: Simulates getting data from remote-api
Gotchas:
The example code is not reliant on a backend. It simply tests with data from a file and simulates network calls by sleeping for some seconds
The example uses some dependencies in order to speed up the creation of this example. But its basic stuff like AFNetwork, Json parsing, Autollayout. All of which could easily be substituted
Requirements:
Backend-API that can provide the count of items
Backend-API that can return items for a range (startIndex, endIndex)