I implement pull to refresh in collection View and the problem I'm facing is my app will crash with out of index message. Below is my cellForItem method
override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: reuseIdentifier, for: indexPath) as! CauNguyenCell
cell.postArray = postData[indexPath.item]
return cell
}
override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return postData.count
}
I know the problem is because I use removeAll method to clear all data from my postData but I have to that so my data array will have completely new data.
Below is my refresh function:
func handleRefresh(_ refreshControl: UIRefreshControl) {
refreshControl.beginRefreshing()
postData.removeAll()
fetchDataAgain()
self.collectionView.reloadData()
refreshControl.endRefreshing()
}
error message: Thread 1: Fatal error: Index out of range
I just want to ask if anyone has any suggestions to solve the problem. Thanks!
I have implemented same thing in my project. First I have created refreshControl instance globally, then setup in initSetup() method call from viewDidLoad() in my view controller.
var refreshControl : UIRefreshControl?
var arrWeddingInvitations = [MyModelClass]()
func initialSetup() {
self.refreshControl = UIRefreshControl()
self.refreshControl?.tintColor = .yellow
self.refreshControl?.addTarget(self, action: #selector(getWeddingInvitations), for: .valueChanged)
self.cvWeddingInvitation.addSubview(refreshControl!)
}
This is call getWeddingInvitations() method which is fetching data from server.
// This code will hide refresh controller
DispatchQueue.main.async {
self.refreshControl?.endRefreshing()
}
// This code in my API request completion block and will check responded array data, If it is not nil then assigned to my global array in view controller which are used to display data and reload collection view.
if arrInvitations != nil, arrInvitations.count > 0 {
self.lblEmptyData.isHidden = true
self.cvWeddingInvitation.isHidden = false
self.arrWeddingInvitations = arrInvitations
self.cvWeddingInvitation.reloadData()
} else {
self.lblEmptyData.isHidden = false
self.cvWeddingInvitation.isHidden = true
}
This is working code in my current project. I hope this will help you.
See following video:
Pull to refresh test video
Please check your UICollectionViewDataSource implementation for these methods:
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int
func numberOfSections(in: UICollectionView)
In the first one you should return the current number of items postData.count, the second one in your case should return 1.
Edit you code like this:
func fetchDataAgain(completion: ((Bool) -> ())) {
// your code
if postData != nil, postData.count != 0 {
completion(true)
}
}
func handleRefresh(_ refreshControl: UIRefreshControl) {
refreshControl.beginRefreshing()
postData.removeAll()
fetchDataAgain { (complete) in
if complete {
self.collectionView.reloadData()
refreshControl.endRefreshing()
}
}
}
Method fetchDataAgain will check array, and if it != nil and count != 0 in handler complete reloadData.
Code do all step by step, and when you are reload data in collection, your array can be empty, or nil. As a rule better to use handlers
Related
i am making app with Xcode using Swift , i fetch posts from my WordPress Website, i am very new to Xcode and Swift , i have fetched posts from my Website Successfully , now the problem is that when is try to load more posts (More than 10 posts) , i mean pagination, i see some problems, like when i do pagination after 10th post, it show the next 11-20 posts but it not starts from post 11th but it goes directly to post 20 and because of that , all next posts loaded automatically untill the end of posts, and one more thing when next posts are loading than i can't see the old posts like when 11-20 posts loaded then 1-10 posts are not shown and CollectionView starts from number 11.
this is my code to fetch posts..
func fetchPostData(completionHandler: #escaping ([Post]) -> Void ) {
self.page += 1
let url = URL(string: "https://www.sikhnama.com/wp-json/wp/v2/posts/?categories=6&page=\(page)")!
let task = URLSession.shared.dataTask(with: url) { (data, response, error) in
guard let data = data else {return}
do {
let postsData = try JSONDecoder().decode([Post].self, from: data)
completionHandler(postsData)
DispatchQueue.main.async {
self.collectionView.reloadData()
}
}
catch {
let error = error
print(String(describing: error))
}
}.resume()
}
in ViewDid Load
self.fetchPostData { (posts) in
self.newsData = posts }
and this is how i do pagination
func collectionView(_ collectionView: UICollectionView, willDisplay cell: UICollectionViewCell, forItemAt indexPath: IndexPath) {
if indexPath.row == self.newsData.count - 1 { //numberofitem count
updateNextSet()
}
}
func updateNextSet(){
self.fetchPostData { (posts) in
self.newsData = posts
}
}
CollectionView Code
extension ViewController: UICollectionViewDataSource {
func numberOfSections(in collectionView: UICollectionView) -> Int {
return 1
}
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int{
return self.newsData.count
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "MovieCollectionViewCell", for: indexPath) as! MovieCollectionViewCell
cell.setup(with: newsData[indexPath.row])
return cell
}
please help . thanks
When the next batch of posts come back, you are overwriting the existing posts rather than appending them:
self.fetchPostData { (posts) in
self.newsData = posts
}
Instead, you need to append the new posts instead such as by using the += operator.
In addition, you should call reloadData() within the fetchPostData completion handler rather than inside the response of the HTTP request to give your code better separation of concerns.
So the above code would become:
self.fetchPostData { (posts) in
self.newsData += posts
self.collectionView.reloadData()
}
I'm using a UICollectionViewDiffableDataSource and a NSFetchedResultsController to populate my UICollectionView inside my UIViewController.
To add the ability of reordering cells I added a UILongPressGestureRecognizer and subclassed UICollectionViewDiffableDataSource in order to use it's canMoveItemAt: and moveItemAt: methods.
When reordering a cell the following things happen:
moveItemAt: is called and I update the objects position property and save the MOC
controllerDidChangeContent: of the NSFetchedResultsControllerDelegate is called and I create a new snapshot from the current fetchedObjects and apply it.
When I apply dataSource?.apply(snapshot, animatingDifferences: true) the cells switch positions back immediately. If I set animatingDifferences: false it works, but all cells are reloaded visibly.
Is there any best practice here, how to implement cell reordering on a UICollectionViewDiffableDataSource and a NSFetchedResultsController?
Here are my mentioned methods:
// ViewController
func createSnapshot(animated: Bool = true) {
var snapshot = NSDiffableDataSourceSnapshot<Int, Favorite>()
snapshot.appendSections([0])
snapshot.appendItems(provider.fetchedResultsController.fetchedObjects ?? [])
dataSource?.apply(snapshot, animatingDifferences: animated)
}
// NSFetchedResultsControllerDelegate
func controllerDidChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>) {
createSnapshot(animated: false)
}
// Subclassed UICollectionViewDiffableDataSource
override func collectionView(_ collectionView: UICollectionView, moveItemAt sourceIndexPath: IndexPath, to destinationIndexPath: IndexPath) {
provider.moveFavorite(from: sourceIndexPath.row, to: destinationIndexPath.row)
}
// Actual cell moving in a provider class
public func moveFavorite(from source: Int, to destination: Int) {
guard let favorites = fetchedResultsController.fetchedObjects else { return }
if source < destination {
let partialObjects = favorites.filter({ $0.position <= destination && $0.position >= source })
for object in partialObjects {
object.position -= 1
}
let movedFavorite = partialObjects.first
movedFavorite?.position = Int64(destination)
}
else {
let partialObjects = favorites.filter({ $0.position >= destination && $0.position <= source })
for object in partialObjects {
object.position += 1
}
let movedFavorite = partialObjects.last
movedFavorite?.position = Int64(destination)
}
do {
try coreDataHandler.mainContext.save()
} catch let error as NSError {
print(error.localizedDescription)
}
}
My solution to the same issue is to subclass the UICollectionViewDiffableDataSource and implement the canMoveItemAt method in the subclass to answer true.
The animation seems to work fine for me if the longPressAction case of .ended does three things:
update the model
call dateSource.collectionView(..moveItemAt:..)
run your dataSource.apply
The other usual methods for drag behavior have to be also implemented which it looks like you have done. FYI for others- These methods are well documented in the section for 'Reordering Items Interactively' of UICollectionView. https://developer.apple.com/documentation/uikit/uicollectionview
class PGLDiffableDataSource: UICollectionViewDiffableDataSource<Int, Int> {
override func collectionView(_ collectionView: UICollectionView, canMoveItemAt indexPath: IndexPath) -> Bool {
return true
}
}
No need to subclass. Starting in iOS 14.0, UICollectionViewDiffableDataSource supports reordering handlers you can implement.
let data_source = UICollectionViewDiffableDataSource<MySection, MyModelObject>( collectionView: collection_view, cellProvider:
{
[weak self] (collection_view, index_path, video) -> UICollectionViewCell? in
let cell = collection_view.dequeueReusableCell( withReuseIdentifier: "cell", for: index_path ) as! MyCollectionViewCell
if let self = self
{
//setModel() is my own method to update the view in MyCollectionViewCell
cell.setModel( self.my_model_objects[index_path.item] )
}
return cell
})
// Allow every item to be reordered as long as there's 2 or more
diffable_data_source.reorderingHandlers.canReorderItem =
{
item in
my_model_objects.count >= 2 return true
}
//Update your model objects before the reorder occurs.
//You can also use didReorder, but it might be useful to have your
//model objects in the correct order before dequeueReusableCell() is
//called so you can update the cell's view with the correct model object.
diffable_data_source.reorderingHandlers.willReorder =
{
[weak self] transaction in
guard let self = self else { return }
self.my_model_objects = transaction.finalSnapshot.itemIdentifiers
}
I'm trying to combine a CollectionViewwith a TableView, so fare everything works except one problem, which I cant fix myself.
I have to load some data in the CollectionViews which are sorted with the header of the TableViewCell where the CollectionView is inside. For some reason, every time I start the app, the first three TableViewCells are identical. If I scroll a little bit vertically, they change to the right Data.
But it can also happen that while using it sometimes displays the same Data as in on TableViewCell another TableViewCell, here again the problem is solved if I scroll a little.
I think the problem are the reusableCells but I cant find the mistake myself. I tried to insert a colletionView.reloadData() and to set the cells to nil before reusing, sadly this didn`t work.
My TableViewController
import UIKit
import RealmSwift
import Alamofire
import SwiftyJSON
let myGroupLive = DispatchGroup()
let myGroupCommunity = DispatchGroup()
var channelTitle=""
class HomeVTwoTableViewController: UITableViewController {
var headers = ["LIVE","Channel1", "Channel2", "Channel3", "Channel4", "Channel5", "Channel6"]
override func viewDidLoad() {
super.viewDidLoad()
}
override func viewWillAppear(_ animated: Bool) {
self.navigationController?.navigationBar.isTranslucent = false
DataController().fetchDataLive(mode: "get")
DataController().fetchDataCommunity(mode: "get")
}
//MARK: Custom Tableview Headers
override func tableView(_ tableView: UITableView, titleForHeaderInSection section: Int) -> String? {
return headers[section]
}
//MARK: DataSource Methods
override func numberOfSections(in tableView: UITableView) -> Int {
return headers.count
}
override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return 1
}
//Choosing the responsible PrototypCell for the Sections
override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
if indexPath.section == 0 {
let cell = tableView.dequeueReusableCell(withIdentifier: "cellBig", for: indexPath) as! HomeVTwoTableViewCell
print("TableViewreloadMain")
cell.collectionView.reloadData()
return cell
}
else if indexPath.section >= 1 {
// getting header Titel for reuse in cell
channelTitle = self.tableView(tableView, titleForHeaderInSection: indexPath.section)!
let cell = tableView.dequeueReusableCell(withIdentifier: "cellSmall", for: indexPath) as! HomeVTwoTableViewCellSmall
// anti Duplicate protection
cell.collectionView.reloadData()
return cell
}
else {
channelTitle = self.tableView(tableView, titleForHeaderInSection: indexPath.section)!
let cell = tableView.dequeueReusableCell(withIdentifier: "cellSmall", for: indexPath) as! HomeVTwoTableViewCellSmall
// anti Duplicate protection
cell.collectionView.reloadData()
return cell
}
}
}
}
My TableViewCell with `CollectionView
import UIKit
import RealmSwift
var communities: Results<Community>?
class HomeVTwoTableViewCellSmall: UITableViewCell{
//serves as a translator from ChannelName to the ChannelId
var channelOverview: [String:String] = ["Channel1": "399", "Channel2": "401", "Channel3": "360", "Channel4": "322", "Channel5": "385", "Channel6": "4"]
//Initiaize the CellChannel Container
var cellChannel: Results<Community>!
//Initialize the translated ChannelId
var channelId: String = ""
#IBOutlet weak var collectionView: UICollectionView!
}
extension HomeVTwoTableViewCellSmall: UICollectionViewDataSource,UICollectionViewDelegate {
//MARK: Datasource Methods
func numberOfSections(in collectionView: UICollectionView) -> Int
{
return 1
}
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int
{
return (cellChannel.count)
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell
{
guard let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "collectionCellSmall", for: indexPath) as? HomeVTwoCollectionViewCellSmall else
{
fatalError("Cell has wrong type")
}
//removes the old image and Titel
cell.imageView.image = nil
cell.titleLbl.text = nil
//inserting the channel specific data
let url : String = (cellChannel[indexPath.row].pictureId)
let name :String = (cellChannel[indexPath.row].communityName)
cell.titleLbl.text = name
cell.imageView.downloadedFrom(link :"link")
return cell
}
//MARK: Delegate Methods
override func layoutSubviews() {
myGroupCommunity.notify(queue: DispatchQueue.main, execute: {
let realm = try! Realm()
//Getting the ChannelId from Dictionary
self.channelId = self.channelOverview[channelTitle]!
//load data from Realm into variables
self.cellChannel = realm.objects(Community.self).filter("channelId = \(String(describing: self.channelId)) ")
self.collectionView.dataSource = self
self.collectionView.delegate = self
print("collectionView layout Subviews")
self.collectionView.reloadData()
})
}
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
selectedCommunity = (cellChannel[indexPath.row].communityId)
let home = HomeViewController()
home.showCommunityDetail()
}
}
Thanks in advance.
tl;dr make channelTitle a variable on your cell and not a global variable. Also, clear it, and your other cell variables, on prepareForReuse
I may be mistaken here, but are you setting the channelTitle on the cells once you create them? As I see it, in your viewController you create cells based on your headers, and for each cell you set TableViewController's channelTitle to be the title at the given section.
If this is the case, then the TableViewCell actually isn't receiving any information about what it should be loading before you call reloadData().
In general, I would also recommend implementing prepareForReuse in your HomeVTwoTableViewCellSmall, since it will give you a chance to clean up any stale data. Likely you would want to do something like set cellChannel and channelId to empty strings or nil in that method, so when the cell is reused that old data is sticking around.
ALSO, I just reread the cell code you have, and it looks like you're doing some critical initial cell setup in layoutSubviews. That method is going to be potentially called a lot, but you really only need it to be called once (for the majority of what it does). Try this out:
override the init with reuse identifier on the cell
in that init, add self.collectionView.dataSource = self and self.collectionView.delegate = self
add a didSet on channelTitle
set channelTitle in the viewController
So the code would look like:
var channelTitle: String = "" {
didSet {
self.channelId = self.channelOverview[channelTitle]!
self.cellChannel = realm.objects(Community.self).filter("channelId = \(String(describing: self.channelId)) ")
self.collectionView.reloadData()
}
}
This way you're only reloading your data when the cell is updated with a new channel, rather than every layout of the cell's views.
Sorry... one more addition. I wasn't aware of how your channelTitle was actually being passed. As I see it, you're using channelTitle as a global variable rather than a local one. Don't do that! remove channelTitle from where it is currently before implementing the code above. You'll see some errors, because you're setting it in the ViewController and accessing it in the cell. What you want is to set the channelTitle on the cell from the ViewController (as I outlined above). That also explains why you were seeing the same data across all three cells. Basically you had set only ONE channelTitle and all three cells were looking to that global value to fetch their data.
Hope that helps a little!
(also, you should be able to remove your else if block in the cellForRowAtIndexPath method, since the else block that follows it covers the same code. You can also delete your viewDidLoad, since it isn't doing anything, and you should, as a rule, see if you can get rid of any !'s because they're unsafe. Use ? or guard or if let instead)
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)
I have a TableView where I am fetching data from api. Everything working fine with fetching/displaying data and pagination/infinite-scroll. However, when I try to use my RefreshControl, it crashes with an error:
Array index out of range
var theRefreshControl: UIRefreshControl!
var results: [JSON]! = []
// more stuff..
func refresh(sender: AnyObject) {
if isFirstLoad == false {
self.results = []
currentPage = 1
getPosts()
}
self.theRefreshControl.endRefreshing()
}
override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell : PostCell = tableView.dequeueReusableCellWithIdentifier("PostCell") as! PostCell
cell.delegate = self
print(indexPath.row) // check below.
let post = self.results![indexPath.row] // 'array index out of range' here.
}
To get more detail about the error, I tried adding print(indexPath.row). What I receive is, I receive from 0 to 10 in first load, and then as soon as I refresh, it gets weird:
Also, when I click on the (i):
{length = 2, path = 0 - 9}
Interestingly, exactly same approach works in my other TableViewControllers, only this one is bugging. What may be the problem?
func getPosts() {
isLoading = true
Alamofire.request(.GET, link & params: ["page":"\(currentPage ?? 1)"])
.responseJSON { response in
// error checks
if let data = json["data"].arrayValue as [JSON]? {
self.lastPage = json["last_page"].int!
self.currentPage = json["current_page"].int!
if self.currentPage == 1 {
self.results = data
self.tableView.reloadData()
} else {
var currentCount = self.results!.count;
var indxesPath : [NSIndexPath] = [NSIndexPath]()
for result in data {
indxesPath.append(NSIndexPath(forRow:currentCount,inSection:0));
self.results?.append(result)
currentCount++
}
self.tableView.insertRowsAtIndexPaths(indxesPath, withRowAnimation: UITableViewRowAnimation.Bottom)
}
Edit: Please note that I tried results.removeAll() as well as results.removeAll(keepCapacity: false) in refresh button action function, but no luck. I am still getting the same error and same log for `print(indexPath.row) - 0 to 10 in first load, and in refresh, weirdly 6, 7, 8, [], 9
Swift 3.0 - Same issue here, solved in a similar way to #mcclux but with one less step.
Use the inbuilt UIRefreshControl.
var refreshControl: UIRefreshControl!, then within viewDidLoad configure it:
refreshControl = UIRefreshControl.init()
refreshControl.attributedTitle = NSAttributedString(string: "Pull to refresh")
refreshControl.addTarget(self, action: #selector(yourViewControllerName.yourFunctionToCallOnRefresh), for: UIControlEvents.valueChanged)
tableView.addSubview(refreshControl)
Then you can wrap your code within cellForRowAt indexPath with
if !self.refreshControl.isRefreshing {
...
}
Worked perfectly for me after struggling through it crashing for hours. Hope this helps!
I had a similar issue; it was caused in my case by tableView being called during the refresh, during the period when the content was being reset. Because the index was empty for a period, the app was occasionally throwing index out of range. It didn't happen every time. I solved it by creating a boolean var (isRefreshing) that gets set to true when the refresh starts and then set to false once the refresh is over. Inside of tableView() I have a wrapper for the functionality. In your case it would look like:
override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
if !self.isRefreshing {
let cell : PostCell = tableView.dequeueReusableCellWithIdentifier("PostCell") as! PostCell
cell.delegate = self
print(indexPath.row) // check below.
let post = self.results![indexPath.row] // 'array index out of range' here.
}
}
Edit: here's how I'm using it. The cell creation and return are outside of the if:
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCellWithIdentifier("SessionTableViewCell", forIndexPath: indexPath) as! SessionTableViewCell
if !self.isReloading {
...
}
return cell
}
Solved my problem by deletingself.results = [] from refresh() function. Interestingly, if I empty the array before I refresh, it was creating a problem, but if I directly overwrite the data in the array, it works!
I was facing similar issue when the backing array was emptied like what you did w/ self.results = []. In my finding, there are 2 additional ways to solve this issue.
//1. is to reload table view as soon as you empty the array
func refresh(sender: AnyObject) {
if isFirstLoad == false {
self.results = []
self.tableView.reloadData()
currentPage = 1
getPosts()
}
self.theRefreshControl.endRefreshing()
}
//2. is to delay the execution of the code inside the if scope to give enough time for the table view to get up to date on the count of the results array
func refresh(sender: AnyObject) {
if isFirstLoad == false {
self.delayExecutionByMilliseconds(500) {
self.results = []
currentPage = 1
getPosts()
}
}
self.theRefreshControl.endRefreshing()
}
func delayExecutionByMilliseconds(_ delay: Int, for anonFunc: #escaping () -> Void) {
let when = DispatchTime.now() + .milliseconds(delay)
DispatchQueue.main.asyncAfter(deadline: when, execute: anonFunc)
}
In your refresh function, add self.tableView.reloadData() after cleaning your arrays, and before the function getPosts()