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Implementing the pull-to-refresh gesture for iOS 6

From: iOS SDK and SQLite: Building Data-Driven Apps

Video: Implementing the pull-to-refresh gesture for iOS 6

Now let's take a look at how to implement the iOS 6 pull to refresh feature. I'm going to create a working copy of our BWRSS-features-start, and I'm going to rename that as -02, and we'll open in Xcode by double clicking on the Xcode project file. We're going to be working in the ItemsTableViewController, and we notice up here at the top in our interface section, this is the private members or the instance variables for this class.

Implementing the pull-to-refresh gesture for iOS 6

Now let's take a look at how to implement the iOS 6 pull to refresh feature. I'm going to create a working copy of our BWRSS-features-start, and I'm going to rename that as -02, and we'll open in Xcode by double clicking on the Xcode project file. We're going to be working in the ItemsTableViewController, and we notice up here at the top in our interface section, this is the private members or the instance variables for this class.

You'll notice there's a BOOL variable called canRefresh, and that gets set in -viewDidLoad. If I come down to -viewDidLoad, and we're going to come out to our Finder and load up this methods.txt file, and here is our new -viewDidLoad. I'm going to just copy that and come over here in to Xcode and I will paste that in place. So, you'll notice here I used the respondsToSelector method to check if our TableViewController response to the selector called refreshControl, and if it does, then I know that we can use Refresh so I can set this canRefresh equals true, or Yes in the case of Objective-C.

And I initialize our refreshControl with the UIRefreshControl and then I call addTarget on it to add the target, it is refreshInvoked:forState method, and it will be set for the control events, UIControlEventValueChanged. It looks a little bit complicated, and I guess it is, but this is just how you do it, and you'll pretty much always do it exactly this way. So, we're going to come back out here to our text editor, and I'm going to grab all of this support for reload gestures stuff here, and I'm going to come back into Xcode, and I'm going to paste it in right about here. Here is how this works.

Here's our refreshInvoked forState, and you'll remember that's the selector that we set as our target for the refreshControl event, right? So, when that gets called we reload our RSSFeed, and we send endRefreshing message to the RefreshControl, as simple as that. In order for that to happen, we have to be the first responder and so our class gets called with canBecomeFirstResponder to test whether or not we have that capability and so we use this canRefresh flag to return there.

When viewDidAppear, we're going to call becomeFirstResponder, and when view will disappear we resignFirstResponder. So that's all there is to it. When I save this and run it in the iPhone Simulator--I'm going to go ahead and add my test feed here so that's at ios.bw.org/testfeed, and I'll bring that up. There is five entries, and when I pull you see there is that little icon, and I pull it far enough, and it goes ahead it calls this rerefreshInvoked which reloads the feed and ends the refreshing, and there it is again.

So, we've now successfully added the pull to refresh feature to our app. This was easy for a number of reasons. First of all, Cocoa Touch Framework is really very well written and easy to code to then reloading the RSS Feed was also easy because our code is well-organized. If you do a good job of keeping your code clear and concise, then changing and modifying your code will always be a lot easier.

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This video is part of

Image for iOS SDK and SQLite: Building Data-Driven Apps
iOS SDK and SQLite: Building Data-Driven Apps

41 video lessons · 6402 viewers

Bill Weinman
Author

 
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  1. 8m 29s
    1. Welcome
      57s
    2. Exercise files
      2m 17s
    3. Course overview
      3m 4s
    4. Application overview
      2m 11s
  2. 14m 49s
    1. Prototyping in a testbed
      1m 27s
    2. Building the view controller
      3m 45s
    3. Coding the testbed
      7m 56s
    4. Using the testbed
      1m 41s
  3. 37m 49s
    1. Understanding SQLite in iOS
      1m 41s
    2. Creating an Objective-C interface for SQLite
      9m 57s
    3. Testing the BWDB interface in the sandbox
      7m 1s
    4. Designing a database schema
      8m 7s
    5. Supporting the application with a specific interface
      7m 7s
    6. Using C pointers with automatic reference counting (ARC)
      3m 56s
  4. 21m 18s
    1. Understanding the table view
      1m 33s
    2. Creating the view controller
      6m 39s
    3. Reading from the database
      13m 6s
  5. 33m 50s
    1. Understanding the parsing process
      1m 57s
    2. Creating the item view controller
      12m 25s
    3. Reading data from the internet
      5m 30s
    4. Parsing the feed with NSXMLParser
      8m 2s
    5. Updating the item view with the feed items
      5m 56s
  6. 40m 14s
    1. Understanding the modal view
      1m 47s
    2. Constructing the view controller
      15m 5s
    3. Finding a feed link in a web page
      8m 55s
    4. Parsing the feed with NSXMLParser
      5m 4s
    5. Delegating back to the parent view
      6m 11s
    6. Deleting feeds
      3m 12s
  7. 21m 5s
    1. Creating the web view class
      12m 33s
    2. Coding the web view
      5m 25s
    3. Viewing pages in Safari
      3m 7s
  8. 14m 3s
    1. Understanding the iOS preferences system
      1m 23s
    2. Creating the preferences plist in Xcode
      7m 20s
    3. Reading preferences in your application
      5m 20s
  9. 6m 15s
    1. Adding pull-to-refresh functionality
      2m 34s
    2. Implementing the pull-to-refresh gesture for iOS 6
      3m 41s
  10. 27m 1s
    1. Understanding split view
      1m 4s
    2. Coding the table views
      11m 24s
    3. Implementing the iPad detail view
      6m 35s
    4. Implementing the iPad modal view
      7m 58s
  11. 35s
    1. Goodbye
      35s

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