how to retrieve all visible table section header views

Question

is there a way to get all the section header views that are visible?

something similar to UITableView\'s visibleCells instance method..

Answer 1

to get the current visible sections, u could get it by checking the current visible cells indexpath section, so this function could return to u the visible sections

- (NSArray *)indexesOfVisibleSections {

    NSMutableArray *visibleSections = [NSMutableArray array];

    for (UITableViewCell * cell in [self.tableView visibleCells]) {
        if (![visibleSections containsObject:[NSNumber numberWithInteger:[self.tableView indexPathForCell:cell].section]]) {
            [visibleSections addObject:[NSNumber numberWithInteger:[self.tableView indexPathForCell:cell].section]];
        }
    }

    return visibleSections;
}

And to access section view , u can use

- (UITableViewHeaderFooterView *)headerViewForSection:(NSInteger)section;

Answer 2

I really liked @adamsiton's solution and I ended up translating it to swift. Here it is, FYI.

I called the file UITableView+VisibleSections.swift

import UIKit

public extension UITableView {

    var indexesOfVisibleSections: [Int] {
        // Note: We can't just use indexPathsForVisibleRows, since it won't return index paths for empty sections.
        var visibleSectionIndexes = [Int]()

        for i in 0..<numberOfSections {
            var headerRect: CGRect?
            // In plain style, the section headers are floating on the top, so the section header is visible if any part of the section's rect is still visible.
            // In grouped style, the section headers are not floating, so the section header is only visible if it's actualy rect is visible.
            if (self.style == .plain) {
                headerRect = rect(forSection: i)
            } else {
                headerRect = rectForHeader(inSection: i)
            }
            if headerRect != nil {
                // The "visible part" of the tableView is based on the content offset and the tableView's size.
                let visiblePartOfTableView: CGRect = CGRect(x: contentOffset.x, y: contentOffset.y, width: bounds.size.width, height: bounds.size.height)
                if (visiblePartOfTableView.intersects(headerRect!)) {
                    visibleSectionIndexes.append(i)
                }
            }
        }
        return visibleSectionIndexes
    }

    var visibleSectionHeaders: [UITableViewHeaderFooterView] {
        var visibleSects = [UITableViewHeaderFooterView]()
        for sectionIndex in indexesOfVisibleSections {
            if let sectionHeader = headerView(forSection: sectionIndex) {
                visibleSects.append(sectionHeader)
            }
        }

        return visibleSects
    }
}

Answer 3

A quick look at the UITableView documentation gives us the indexPathsForVisibleRows and combining it with map gives us the array we need:

tableView.indexPathsForVisibleRows.map{ tableView.headerView(forSection: $0.section) }

map returns the array of our visible headers-in-section.

Answer 4

For a plain style table, you can get the visible rows. From those, get the set of visible sections. And from that, get the section header views from the table.

NSArray *visibleRows = [self.tableView indexPathsForVisibleRows];
NSMutableIndexSet *sections = [[NSMutableIndexSet alloc] init];
for (NSIndexPath *indexPath in visibleRows) {
    [sections addIndex:indexPath.section];
}

NSMutableArray *headerViews = [NSMutableArray array];
[sections enumerateIndexesUsingBlock:^(NSUInteger idx, BOOL *stop) {
    UIView *view = [self.tableView headerViewForSection:idx];
    [headerViews addObject:view];
}];

Note: code not tested - may contain typos. This won't work 100% for a grouped style table.