您可以通过添加检查cellForRowAtIndexPath:方法中的位置来实现.这种方法易于理解和实现:

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    // Classic start method
    static NSString *cellIdentifier = @"MyCell";
    MyCell *cell = [tableView dequeueReusableCellWithIdentifier:cellIdentifier];
    if (!cell)
    {
        cell = [[MyCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:MainMenuCellIdentifier];
    }

    MyData *data = [self.dataArray objectAtIndex:indexPath.row];
    // Do your cell customisation
    // cell.titleLabel.text = data.title;

    BOOL lastItemReached = [data isEqual:[[self.dataArray] lastObject]]; 
    if (!lastItemReached && indexPath.row == [self.dataArray count] - 1)
    {
        [self launchReload];
    }
}

编辑:添加了对最后一项的检查以防止递归调用.您必须实现定义是否已到达最后一个项目的方法.

EDIT2:解释了lastItemReached

迅速

方法1:滚动到底部

这是Swro版本的PedroRomão的答案.当用户停止滚动时,它会检查它是否已到达底部.

func scrollViewDidEndDragging(scrollView: UIScrollView, willDecelerate decelerate: Bool) {

    // UITableView only moves in one direction, y axis
    let currentOffset = scrollView.contentOffset.y
    let maximumOffset = scrollView.contentSize.height - scrollView.frame.size.height

    // Change 10.0 to adjust the distance from bottom
    if maximumOffset - currentOffset <= 10.0 {
        self.loadMore()
    }
}

方法2:到达最后一行

这是swinguX的答案的Swift版本.它检查用户是否已到达最后一行.

func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {

    // set up cell
    // ...

    // Check if the last row number is the same as the last current data element
    if indexPath.row == self.dataArray.count - 1 {
        self.loadMore()
    }

}

loadMore()方法示例

我设置了这三个类变量来获取批量数据.

// number of items to be fetched each time (i.e., database LIMIT)
let itemsPerBatch = 50

// Where to start fetching items (database OFFSET)
var offset = 0

// a flag for when all database items have already been loaded
var reachedEndOfItems = false

这是将更多项目从数据库加载到表视图中的功能.

func loadMore() {

    // don't bother doing another db query if already have everything
    guard !self.reachedEndOfItems else {
        return
    }

    // query the db on a background thread
    DispatchQueue.global(qos: .background).async {

        // determine the range of data items to fetch
        var thisBatchOfItems: [MyObjects]?
        let start = self.offset
        let end = self.offset + self.itemsPerBatch

        // query the database
        do {
            // SQLite.swift wrapper
            thisBatchOfItems = try MyDataHelper.findRange(start..<end)
        } catch _ {
            print("query failed")
        }

        // update UITableView with new batch of items on main thread after query finishes
        DispatchQueue.main.async {

            if let newItems = thisBatchOfItems {

                // append the new items to the data source for the table view
                self.myObjectArray.appendContentsOf(newItems)

                // reload the table view
                self.tableView.reloadData()

                // check if this was the last of the data
                if newItems.count < self.itemsPerBatch {
                    self.reachedEndOfItems = true
                    print("reached end of data. Batch count: \(newItems.count)")
                }

                // reset the offset for the next data query
                self.offset += self.itemsPerBatch
            }

        }
    }
}

最好使用willDisplayCell方法来检查是否将加载哪个单元格.一旦我们得到indexPath.row最后的电流,我们可以加载更多的单元格.这将在向下滚动时加载更多单元格.

 - (void)tableView:(UITableView *)tableView 
       willDisplayCell:(UITableViewCell *)cell    
       forRowAtIndexPath:(NSIndexPath *)indexPath
{
    // check if indexPath.row is last row
    // Perform operation to load new Cell's.
}

- (void)tableView:(UITableView *)tableView willDisplayCell:(UITableViewCell *)cell forRowAtIndexPath:(NSIndexPath *)indexPath {
    NSInteger lastSectionIndex = [tableView numberOfSections] - 1;
    NSInteger lastRowIndex = [tableView numberOfRowsInSection:lastSectionIndex] - 1;
    if ((indexPath.section == lastSectionIndex) && (indexPath.row == lastRowIndex)) {
        // This is the last cell
        [self loadMore];
    }
}

如果您使用的是Core Data NSFetchedResultsController,则loadMore可能如下所示:

// Load more
- (void)loadMore {
    [self.fetchedResultsController.fetchRequest setFetchLimit:newFetchLimit];
    [NSFetchedResultsController deleteCacheWithName:@"cache name"];
    NSError *error;
    if (![self.fetchedResultsController performFetch:&error]) {
        // Update to handle the error appropriately.
        NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
    }

    [self.tableView reloadData];
}

细节

Xcode 10,Swift 4.2

解

使用UIScrollView/UICollectionView/UITableView

import UIKit

protocol LoadMoreControlDelegate: class {
    func loadMoreControl(didStartAnimating loadMoreControl: LoadMoreControl)
    func loadMoreControl(didStopAnimating loadMoreControl: LoadMoreControl)
}

class LoadMoreControl {

    private let spacingFromLastCell: CGFloat
    private let indicatorHeight: CGFloat
    private weak var activityIndicatorView: UIActivityIndicatorView?
    private weak var scrollView: UIScrollView?
    weak var delegate: LoadMoreControlDelegate?

    private var defaultY: CGFloat {
        guard let height = scrollView?.contentSize.height else { return 0.0 }
        return height + spacingFromLastCell
    }

    init (scrollView: UIScrollView, spacingFromLastCell: CGFloat, indicatorHeight: CGFloat) {
        self.scrollView = scrollView
        self.spacingFromLastCell = spacingFromLastCell
        self.indicatorHeight = indicatorHeight

        let size:CGFloat = 40
        let frame = CGRect(x: (scrollView.frame.width-size)/2, y: scrollView.contentSize.height + spacingFromLastCell, width: size, height: size)
        let activityIndicatorView = UIActivityIndicatorView(frame: frame)
        activityIndicatorView.color = .black
        activityIndicatorView.hidesWhenStopped = true
        activityIndicatorView.autoresizingMask = [.flexibleLeftMargin, .flexibleRightMargin]
        scrollView.addSubview(activityIndicatorView)
        activityIndicatorView.isHidden = isHidden
        self.activityIndicatorView = activityIndicatorView
    }

    private var isHidden: Bool {
        guard let scrollView = scrollView else { return true }
        return scrollView.contentSize.height < scrollView.frame.size.height
    }

    func didScroll() {
        guard let scrollView = scrollView, let activityIndicatorView = activityIndicatorView else { return }
        let offsetY = scrollView.contentOffset.y
        activityIndicatorView.isHidden = isHidden
        if !activityIndicatorView.isHidden && offsetY >= 0 {
            let contentDelta = scrollView.contentSize.height - scrollView.frame.size.height
            let offsetDelta = offsetY - contentDelta

            let newY = defaultY-offsetDelta
            if newY < scrollView.frame.height {
                activityIndicatorView.frame.origin.y = newY
            } else {
                if activityIndicatorView.frame.origin.y != defaultY {
                    activityIndicatorView.frame.origin.y = defaultY
                }
            }

            if !activityIndicatorView.isAnimating {
                if offsetY > contentDelta && offsetDelta >= indicatorHeight && !activityIndicatorView.isAnimating {
                    activityIndicatorView.startAnimating()
                    delegate?.loadMoreControl(didStartAnimating: self)
                }
            }

            if scrollView.isDecelerating {
                if activityIndicatorView.isAnimating && scrollView.contentInset.bottom == 0 {
                    UIView.animate(withDuration: 0.3) { [weak self, weak scrollView] in
                        if let bottom = self?.indicatorHeight {
                            scrollView?.contentInset = UIEdgeInsets(top: 0, left: 0, bottom: bottom, right: 0)
                        }
                    }
                }
            }
        }
    }

    func stop() {
        guard let scrollView = scrollView else { return }
        let contentDelta = scrollView.contentSize.height - scrollView.frame.size.height
        let offsetDelta = scrollView.contentOffset.y - contentDelta
        if offsetDelta >= 0 {
            UIView.animate(withDuration: 0.3, animations: { [weak scrollView] in
                scrollView?.contentInset = .zero
            }) { [weak self] result in
                if result { self?.endAnimating() }
            }
        } else {
            scrollView.contentInset = .zero
            endAnimating()
        }
    }

    private func endAnimating() {
        activityIndicatorView?.stopAnimating()
        delegate?.loadMoreControl(didStopAnimating: self)
    }
}

用法

loadMoreControl = LoadMoreControl(scrollView: tableView, spacingFromLastCell: 10, indicatorHeight: 60)
loadMoreControl.delegate = self

完整样本

extension ViewController: LoadMoreControlDelegate {
    func loadMoreControl(didStartAnimating loadMoreControl: LoadMoreControl) {
        print("didStartAnimating")
    }

    func loadMoreControl(didStopAnimating loadMoreControl: LoadMoreControl) {
        print("didStopAnimating")
    }
}

extension ViewController: UITableViewDelegate {
    func scrollViewDidScroll(_ scrollView: UIScrollView) {
        loadMoreControl.didScroll()
    }
}

结果

下面的链接将提供示例代码.#Swift3

用户需要拉出最后一个表格视图单元格,至少需要2个单元格才能从服务器获取更多数据.

您还会发现Process cell也显示加载过程,如同最后一个单元格一样.

它在Swift3中

https://github.com/yogendrabagoriya/YBTableViewPullData