Quickies for UITableView

Borkware »
Quickies »
Quickies for UITableView

General

Adding a long-press to a UITableViewCell that pops up a UIMenuController [permalink]
To add a long-press that pops up a UIMenuController, You'll need to subclass UITableViewCell, but you're probably already doing that. Add the gesture recognizer, and a notification handler that'll unselect the cell:

        UILongPressGestureRecognizer *longPressGesture =
            [[[UILongPressGestureRecognizer alloc] initWithTarget: self
                                                   action: @selector(longPress:)]
                autorelease];
        [self addGestureRecognizer: longPressGesture];

        NSNotificationCenter *center = [NSNotificationCenter defaultCenter];
        [center addObserver: self
                selector: @selector(unselectSelf:)
                name: UIMenuControllerWillHideMenuNotification
                object: nil];

- (void) unselectSelf: (NSNotification *) notification {
    self.selected = NO;
} // unselectSelf

In the long press handler, check the state (to prevent multiple firings of the gesture recognizer from making the menus spaz out), and then set up the menu thing.

- (void) longPress: (UILongPressGestureRecognizer *) recognizer {

    if (recognizer.state != UIGestureRecognizerStateBegan) return;

    Put the stuff from  Adding a pop up menu thingie here

    self.selected = YES;  // Highlight to make it doubly-obvious what's being menu'd

} // longPress

Adding an arrow thingie or checkbox to tableview cells [permalink]
If you have the cell, you can set the accessoryType directly:
```
UITableViewCell *cell = ...;
cell.accessoryType = UITableViewCellAccessoryDisclosureIndicator;
```
The delegate method (accessoryTypeForRowWithIndexPath) has been deprecated, so don't use that.
Use UITableViewCellAccessoryCheckmark for a checkmark.
Use UITableViewCellAccessoryNone to remove the checkmark.
Adding an index to a tableview [permalink]
Some tableviews have the short-cut list thingie on the side, which apple calls the index. The index is section-based - each entry in the index corresponds to a section in your data. So if you have a pretty flat list (just an NSArray, for instance), you'll either need to map section-> index, or split up your data so it's physically organized in section/row.
And then override these. In this case, I split up an array into an array of arrays, each sub-array being the contents of a section that corresponds to a string to display in the index. _tableIndex is an array of strings for display of the index.
```
- (NSArray *) sectionIndexTitlesForTableView: (UITableView *) tableView {
    return _tableIndex;
} // sectionIndexTitles


- (NSInteger) tableView: (UITableView *) tableView
sectionForSectionIndexTitle: (NSString *) title
                atIndex: (NSInteger) index {
    return index;
} // sectionForSectionIndexTitle
```

Changing UITableViewCell label text color [permalink]

    if (someProperty) cell.textLabel.textColor = [UIColor grayColor];
    else cell.textLabel.textColor = [UIColor blackColor];

Controlling UITableView row rearranging [permalink]
Say that you want to let the user rearrange tableview rows except for the first and the last, which can't move. First, inhibit the drawing of the little rearrange indicator on the first and last rows:

- (BOOL) tableView: (UITableView *) tableView
  canMoveRowAtIndexPath: (NSIndexPath *) indexPath {

    if (indexPath.row == 0) return NO;
    else if (indexPath.row == _cues.count - 1) return NO;
    else return YES;

} // canMoveRowAtIndexPath

And then prevent rows from being dragged to the first and last position:

- (NSIndexPath *) tableView: (UITableView *) tableView
targetIndexPathForMoveFromRowAtIndexPath: (NSIndexPath *) source
        toProposedIndexPath: (NSIndexPath *) destination {

    if (destination.row > 0 && destination.row < _cues.count - 1) {
        // No violence necessary.
        return destination;
    }

    NSIndexPath *indexPath = nil;

    // If your table can have <= 2 items, you might want to robusticize the index math.
    if (destination.row == 0) {
        indexPath = [NSIndexPath indexPathForRow: 1  inSection: 0];
    } else {
        indexPath = [NSIndexPath indexPathForRow: _cues.count - 2
                                 inSection: 0];
    }

    return indexPath;

} // targetIndexPathForMoveFromRowAtIndexPathPleaseOHaiThanksForMovingKthxBai

Creating a new index path [permalink]

    NSIndexPath *indexPath = [NSIndexPath indexPathForRow: row
                                          inSection: 0];

Filter a table view selection [permalink]
You might have some rows in a UITableView you don't want to be selected. Override willSelectRowAtIndexPath, return nil to reject the selection, return the passed-in indexPath to use as-is, or return your choice of selected cells.
```
- (NSIndexPath *) tableView: (UITableView *) tableView
   willSelectRowAtIndexPath: (NSIndexPath *) indexPath {
    // don't select the top row sort control.
    if (indexPath.row == 0) return nil;
    else return indexPath;
} // willSelectRowAtIndexPath
```

Finding the row from a tableview cell button [permalink]
You can add buttons to a UITableViewCell. The fun part is figuring out what row that button lives on. Assuming that the button is added right to the cell, you can look at the button's superview to get the cell, and then ask the tableview for the cell's section and row.

- (IBAction) elaborateType: (id) sender {
    if (![sender isKindOfClass: [UIButton class]]) return;  // be paranoid

    UITableViewCell *cell = (UITableViewCell *)[sender superview];
    if (![cell isKindOfClass: [UITableViewCell class]]) return;  // be paranoid

    NSIndexPath *indexPath = [self.kindPickerTableView indexPathForCell: cell];

    // do something with indexPath.row and/or indexPath.section.

} // elaborateType

Getting selected row from UITableView [permalink]

    NSIndexPath *indexPath = [self.tableView indexPathForSelectedRow];
    if (indexPath != nil) [self doStuff];

Handling UITableView row deletion [permalink]

- (void) tableView: (UITableView *) tableView
commitEditingStyle: (UITableViewCellEditingStyle) editingStyle
 forRowAtIndexPath: (NSIndexPath *) indexPath {
    if (editingStyle == UITableViewCellEditingStyleDelete) {
        [_cues removeObjectAtIndex: indexPath.row];  // manipulate your data structure.
        [tableView deleteRowsAtIndexPaths: [NSArray arrayWithObject: indexPath]
                   withRowAnimation: UITableViewRowAnimationFade];
        [self updateUI];  // Do whatever other UI updating you need to do.
    }
} // commitEditingStyle

Invalidating a single row [permalink]
Sometimes you want to update a single row of a tableview as new information comes in. Such as loading something in the background and you want to update a percentage being shown in the cell. You could -reloadData, but don't. That's an awfully big hammer. Instead just reload a row

       NSIndexPath *indexPath = [NSIndexPath indexPathForRow: row
                                              inSection: 0];
        NSArray *array = [NSArray arrayWithObject: indexPath];
        [_playlistTableView reloadRowsAtIndexPaths: array
                            withRowAnimation: UITableViewRowAnimationNone];

Laying out tableview cell when entering / exiting edit mode [permalink]
Entering and exiting UITableView edit mode has a cool animation. If you've got a custom subclass, your goodies don't move unless you override layoutSubviews in your UITableViewCell subclass. Any view position changes will automatically be animated.

- (void) layoutSubviews {

    // skootch stuff over
    if (self.editing && !self.showingDeleteConfirmation) {
#define MARGIN 40.0
        CGRect frame = CGRectMake (MARGIN + 4.0, 4.0, 70.0, 46.0);
        _profileView.frame = frame;

        frame = CGRectMake (MARGIN + 80.0, 0, 240.0 - MARGIN, 55.0);
        _titleLabel.frame = frame;

    // layout normally
    } else {
        CGRect frame = CGRectMake (4.0, 4.0, 70.0, 46.0);
        _profileView.frame = frame;

        frame = CGRectMake (80.0, 0, 240.0, 55.0);
        _titleLabel.frame = frame;
    }

    [super layoutSubviews];
} // layoutSubviews

The showingDeleteConfirmation test is so you don't move things around if the user does the "swipe-right to show delete button" thing.

Prevent editing / deleting of table rows [permalink]
To prevent a row from being deleted in a UITableView (say a header with sorting controls), override -canEditRowAtIndexPath:

- (BOOL) tableView: (UITableView *) tableView
    canEditRowAtIndexPath: (NSIndexPath *) indexPath {
    if (indexPath.row == 0) return NO;
    else return YES;
} // canEditRowAtIndexPath

Putting UITableView into editing mode [permalink]
UITableView editing mode lets you delete / rearrange / insert rows. Turn it on via
```
    [self.cuesTableView setEditing: YES  animated: YES];
```

Rearranging in UITableView [permalink]
Implementing this method in your UITableView datasource will make the table draw the little rearrange marker on each row.

- (void) tableView: (UITableView *) tableView
moveRowAtIndexPath: (NSIndexPath *) from
       toIndexPath: (NSIndexPath *) to {
    // How to rearrange stuff if you're backed by an NSMutableArray:
    GRCue *cue = [_cues objectAtIndex: from.row];
    [cue retain];  // Let it survive being removed from the array.
    [_cues removeObjectAtIndex: from.row];
    [_cues insertObject: cue  atIndex: to.row];
    [cue release];

} // moveRowAtIndexPath

Responding to table taps [permalink]
Set yourself up as the UITableView delegate first.

- (void)tableView: (UITableView *) tableView
    didSelectRowAtIndexPath: (NSIndexPath *) indexPath {
    // Do something logical with indexPath.row, etc.
} // didSelectRowAtIndexPath

Scrolling to a row in a UITableView [permalink]

    NSIndexPath *someRow = [NSIndexPath indexPathForRow: random() % blah.count
					inSection: 0];
    [self.cuesTableView scrollToRowAtIndexPath: someRow
         atScrollPosition: UITableViewScrollPositionBottom
         animated: YES];

You can also scroll to PositionTop and PositionMiddle. If you crash, make sure you've done a -reloadData on the table view prior to trying to scroll.

Selecting a row in a UITableView [permalink]

    NSIndexPath *indexPath = [NSIndexPath indexPathForRow: index
                                          inSection: 0];
    [self.tableView reloadData];  // necessary if selecting row in -viewDidLoad

    [self.tableView selectRowAtIndexPath: indexPath
                    animated: YES
                    scrollPosition: UITableViewScrollPositionNone];

Setting a cell's background color [permalink]

cell.textLabel.backgroundColor = [UIColor redColor];
cell.contentView.backgroundColor = [UIColor redColor];

Setting a cell's image [permalink]

   UIImage *image = [_assets iconAtIndex: indexPath.row];
    if (image) cell.imageView.image = image;

Table view data source foobage [permalink]
Boilerplate for UITableView DataSource stuff.

// Optional
- (NSInteger) numberOfSectionsInTableView: (UITableView *) tableView {
    return 1;
} // numberOfSectionsInTableView


- (NSInteger) tableView: (UITableView *) tableView
  numberOfRowsInSection: (NSInteger) section {
    return dataArray.count;
} // numberOfRowsInSection


- (UITableViewCell *) tableView: (UITableView *) tableView
          cellForRowAtIndexPath: (NSIndexPath *) indexPath {

    UITableViewCell *cell =
        [tableView dequeueReusableCellWithIdentifier: @"BlahTableViewCell"];

    if (!cell) {
        cell = [[UITableViewCell alloc]
                   initWithStyle: UITableViewCellStyleDefault
                   reuseIdentifier: @"BlahTableViewCell"];
        [cell autorelease];  // Delete for ARC
    }

    cell.textLabel.text = [dataArray objectAtIndex: indexPath.row];

    return cell;

} // cellForRowAtIndexPath

Tableview subtitle cell [permalink]
The subtitle cell has a large label and a smaller gray-text sublabel.

Make the cell with UITableViewCellStyleSubtitle:

        cell = [[[UITableViewCell alloc]
                    initWithStyle: UITableViewCellStyleSubtitle
                    reuseIdentifier: @"UITableViewCell"] autorelease];

and set the label values:

    cell.textLabel.text = @"somewhere";
    cell.detailTextLabel.text = @"over the rainbow";

Turning off UITableView scrolling [permalink]
_tableView.scrollEnabled = NO;

UITableView section header titles [permalink]
UITableView won't display its groovy section headers (or footers) until you supply them via the datasource:

- (NSString *) tableView: (UITableView *) tableview
 titleForHeaderInSection: (NSInteger) section {
    NSArray *sections = [BWTermStorage sections];
    return [sections objectAtIndex: section];
} // titleForHeaderInSection

You can return a title for a footer.

You can also return a view:

- (UIView *) tableView: (UITableView *) tableView 
    viewForHeaderInSection: (NSInteger) section;

UITableViewCell styles [permalink]
I always forget what each different kind of tableview cell looks like. Images shamelessly stolen from MobileHIG.
The appropriate constants are UITableViewCellStyleDefault, UITableViewCellStyleValue1, UITableViewCellStyleValue2, and UITableViewCellStyleSubtitle, and settable properties include imageView, textLabel, and detailTextLabel.

Using a nib for a tableview cell [permalink]
You can use a nib file for table view cells pretty easily in iOS5.

1) Make a nib with a single object at the top, a UITableViewCell. Lay it out as you wish. I use view tags to get to the objects contained therein.

enum {
    kTermLabelTag = 1,
    kDetailLabelTag = 2
};

2) Register the nib for a cell reuse identifier. I do it in my -viewDidLoad.

static NSString *g_cellReuseIdentifier = @"BWLookupCellReuseIdentifier"; // file global

...

    UINib *nib = [UINib nibWithNibName: @"BWLookupTableViewCell"  bundle: nil];
    [self.resultsView registerNib: nib
         forCellReuseIdentifier: g_cellReuseIdentifier];

3) Dequeue the cell as usual

    UITableViewCell *cell =
        [tableView dequeueReusableCellWithIdentifier: g_cellReuseIdentifier];

    if (!cell) {
        cell = [[UITableViewCell alloc]
                   initWithStyle: UITableViewCellStyleSubtitle
                   reuseIdentifier: g_cellReuseIdentifier];
    }

4) Dig into the cell with the tags, and go nuts

    UILabel *termLabel = (UILabel *)[cell viewWithTag: kTermLabelTag];
    UILabel *detailLabel = (UILabel *)[cell viewWithTag: kDetailLabelTag];

    termLabel.text = termString;
    detailLabel.text = definition;

Hacks

Clipping cell image drawing to rounded corners of grouped tables [permalink]
If you have a grouped UITableView, the top and bottom cells of each group are rounded. If you have an image in the cell, it will obliterate the left-hand corners. There's a number of ways to properly fix this : pre-clip your images with some transparency at the corners. Set up a clipping path before drawing the cell, or playing with the image view's cell layer.
Or you can hack it by setting the cell's indent to 1. That scoots the whole cell contents over by 10 pixels, letting you miss the rounded corners. Really handy if you're prototyping, want something to look non-horrible, but don't want to go the full-blown correct solution.

Swift

Preparing for Segue from a UITableView tap [permalink]

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    guard let selectedRow = self.tableView.indexPathForSelectedRow else { return }
    guard let vc = segue.destination as? InfographicViewController else { return }
    
    let counter = counters[selectedRow.row]
    let stats = counter.currentTextStats
    vc.stats = stats
}

UITableView data source [permalink]

    @IBOutlet var sessionsTableView : UITableView!
    let cellReuseIdentifier = "Cell"

...

    override func viewDidLoad() {
        super.viewDidLoad()
        self.sessionsTableView.register(UITableViewCell.self,
                                             forCellReuseIdentifier: cellReuseIdentifier)
    }

...

extension ViewController : UITableViewDataSource {

    func numberOfSections(in tableView: UITableView) -> Int {
        return 1
    }
    
    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return 10
    }
    
    func tableView(_ tableView: UITableView,
                   cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: cellReuseIdentifier, 
                                                 for: indexPath) as UITableViewCell
        
        cell.textLabel?.text = "Spork (indexPath.row)"
        
        return cell
    }

}