You’ve no doubt used at least one app, such as the iOS mail
app, that uses a pull-to-refresh gesture to refresh a UITableview. It provides
a very pleasant interaction and gives a cool, sophisticated look to a
table-based app. It also saves space and reduces clutter in the app’s UI, since
space no longer need be reserved for a toolbar and refresh button.

Prior to iOS 6, adding this kind of functionality to your
own app was truly a nontrivial task requiring a lot of time and effort. As we’ll
see, adding pull-to-refresh using the UIRefreshControl class in iOS6 is literally
a snap. We’ll use a small project to demonstrate just how quickly you can add
this functionality to your own apps in just a few minutes.

RefreshMe

To keep things simple and focus only on what’s necessary to
implement the refresh control, we’ll modify a project that I’ve already created
for you, which you can download for free.
<insert download link>

Download the RefreshMe project, open it in Xcode, and click
on ViewController.m.
RefreshMe is a trivial table-based app that displays a list random numbers and
regenerates them whenever we refresh the table. The screenshots below show the different
views of UIRefreshControl as the user pulls and then releases the control.

Note in our app that ViewController is a subclass of UITableViewController.
This is required in order to use the refreshControl property that is now part
of table view controllers in iOS6.

Adding the Refresh Control

Modify viewDidLoad by adding the code shown below.

– (void)viewDidLoad

{

[super viewDidLoad];

UIRefreshControl *refresh = [[UIRefreshControl alloc] init];

refresh.attributedTitle = [[NSAttributedString alloc] initWithString:@"Pull to Refresh"];

[refresh addTarget:self action:@selector(crunchNumbers)

forControlEvents:UIControlEventValueChanged];

self.refreshControl = refresh;

testNumbers = [[NSMutableArray alloc] init];

[self crunchNumbers];

}

In the code above, we allocate a new UIRefreshControl
object, set its title, and then add an action that will execute our crunchNumbers
method whenever the user pulls to refresh. Note that self.refreshControl is a property of
the UITableView, and all we have to do to enable the pull-to-refresh behavior is
to set this property to our newly-created refresh object. Yes, indeed, it was that simple! Now with pull-to-refresh functionality
added to our table, we can move on to care for just a few other details.

Once the refresh animation is started, it will continue to
run until we stop it, so let’s add a stopRefresh: method as shown below directly
under viewDidLoad:

– (void)stopRefresh

{

[self.refreshControl endRefreshing];

}

The endRefreshing
method on UIRefreshControl stops the animation and hides the control until we refresh
the table again. The remaining detail is to call stopRefresh after the table data is
regenerated, so we’ll add the following line in bold to the crunchNumbers
method:

– (void)crunchNumbers

{

[testNumbers removeAllObjects];

for (int i = 0; i < kMaxNumbers; i++) {

float x = rand();

[testNumbers addObject:[NSNumber numberWithFloat:x]];

}

[self performSelector:@selector(stopRefresh) withObject:nil afterDelay:2.5];

}

Note that we don’t have to call reloadData as we normally would on
the table view because the refresh control handles that for us. And because our
method regenerates the data so quickly, we use performSelector:withObject:afterDelay:
to delay the execution of stopRefresh for 2.5 seconds so that we enough time to
observe the animation.

Build and run the project (Shortcut: press Cmd+R) and pull
down on the table. Note that the refresh will not fire until the control is
pulled past a certain point.

Congratulations! You are now certified to implement
pull-to-refresh in your apps!

Bottom line

If there is any downside of pull-to-refresh, it would be
that it could possibly be considered
not easily discoverable by the user. In other words, the feeling among some developers
and designers is that users won’t realize they can pull down on a table, and if
anything, will only discover the pull-to-refresh feature by accident. At this
point however, with almost a year of iOS6 experience under everyone’s belts, there
is much more awareness of the pull down gesture in both the user and developer
community, and it seems unlikely to generate as much confusion (or support
questions!) as it may have in the past.

So if you’ve been putting off adding pull-to-refresh to your
apps, wait no longer! It’s quick, it’s easy, and it adds some delightful
interaction to your apps.