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iOS 7 Programming Cookbook by Vandad Nahavandipoor

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1.10. Presenting Sharing Options with UIActivityViewController

Problem

You want to be able to allow your users to share content inside your apps with their friends, through an interface similar to that shown in Figure 1-27 that provides different sharing options available in iOS, such as Facebook and Twitter.

The activity view controller displayed on an iOS device

Figure 1-27. The activity view controller displayed on an iOS device

Solution

Create an instance of the UIActivityViewController class and share your content through this class, as we will see in the Discussion section of this recipe.

Note

The instances of UIActivityViewController must be presented modally on the iPhone and inside a popover on an iPad. For more information about popovers, refer to Recipe 1.29.

Discussion

There are many sharing options inside iOS, all built into the core of the OS. For instance, Facebook and Twitter integration is now an integral part of the core of iOS, and you can share pretty much any content from anywhere you want. Third-party apps like ours can also use all the sharing functionalities available in iOS without having to think about the low-level details of these services and how iOS provides these sharing options. The beauty of this whole thing is that you mention what you want to share, and iOS will pick the sharing options that are capable of handling those items. For instance, if you want to share images and text, iOS will display many more items to you than if you want to share an audio file.

Sharing data is very easy in iOS. All you have to do is instantiate the UIActivityViewController class using its initWithActivityItems:applicationActivities: initializer. Here are the parameters to this method:

initWithActivityItems

The array of items that you want to share. These can be instances of NSString, UIImage, or instances of any of your custom classes that conform to the UIActivityItemSource protocol. We will talk about this protocol later in detail.

applicationActivities

An array of instances of UIActivity that represent the activities that your own application supports. For instance, you can indicate here whether your application can handle its own sharing of images and strings. We will not go into detail about this parameter for now and will simply pass nil as its value, telling iOS that we want to stick to the system sharing options.

So let’s say that you have a text field where the user can enter text to be shared, and a Share button right near it. When the user presses the Share button, you will simply pass the text of the text field to your instance of the UIActivityViewController class. Here is our code. We are writing this code for iPhone, so we will present our activity view controller as a modal view controller.

Because we are putting a text field on our view controller, we need to make sure that we are handling its delegate messages, especially the textFieldShouldReturn: method of the UITextFieldDelegate protocol. Therefore, we are going to elect our view controller as the delegate of the text field. Also, we are going to attach an action method to our Share button. Once the button is tapped, we want to make sure there is something in the text field to share. If there isn’t, we will simply display an alert to the user telling him why we cannot share the content of the text field. If there is some text in the text field, we will pop up an instance of the UIActivityViewController class. So let’s begin with the implementation file of our view controller and define our UI components:

@interface ViewController () <UITextFieldDelegate>
@property (nonatomic, strong) UITextField *textField;
@property (nonatomic, strong) UIButton *buttonShare;
@property (nonatomic, strong) UIActivityViewController *activityViewController;
@end

...

After this, we will write two methods for our view controller, each of which is able to create one of our UI components and place it on our view controller’s view. One will create the text field, and the other will create the button next to it:

- (void) createTextField{
    self.textField = [[UITextField alloc] initWithFrame:CGRectMake(20.0f,
                                                                   35.0f,
                                                                   280.0f,
                                                                   30.0f)];
    self.textField.translatesAutoresizingMaskIntoConstraints = NO;
    self.textField.borderStyle = UITextBorderStyleRoundedRect;
    self.textField.placeholder = @"Enter text to share...";
    self.textField.delegate = self;
    [self.view addSubview:self.textField];
}

- (void) createButton{
    self.buttonShare = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    self.buttonShare.translatesAutoresizingMaskIntoConstraints = NO;
    self.buttonShare.frame = CGRectMake(20.0f, 80.0f, 280.0f, 44.0f);
    [self.buttonShare setTitle:@"Share" forState:UIControlStateNormal];

    [self.buttonShare addTarget:self
                         action:@selector(handleShare:)
               forControlEvents:UIControlEventTouchUpInside];

    [self.view addSubview:self.buttonShare];
}

Once we are done with that, we just have to call these two methods in the viewDidLoad method of our view controller. This will allow the UI components to be placed on the view of our view controller:

- (void)viewDidLoad{

    [super viewDidLoad];
    [self createTextField];
    [self createButton];

}

In the textFieldShouldReturn: method, all we do is dismiss the keyboard in order to resign the text field’s active state. This simply means that when a user has been editing the text field and then presses the Return or Enter button on the keyboard, the keyboard should be dismissed. Bear in mind that the createTextField method that we just coded has set our view controller as the delegate of the text field. So we have to implement the aforementioned method as follows:

- (BOOL) textFieldShouldReturn:(UITextField *)textField{
    [textField resignFirstResponder];
    return YES;
}

Last but not least is the handler method of our button. As you saw, the createButton method creates the button for us and elects the handleShare: method to handle the touch down inside action of the button. So let’s code this method:

- (void) handleShare:(id)paramSender{

    if ([self.textField.text length] == 0){
        NSString *message = @"Please enter a text and then press Share";
        UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:nil
                                                            message:message
                                                           delegate:nil
                                                  cancelButtonTitle:@"OK"
                                                  otherButtonTitles:nil];
        [alertView show];
        return;
    }

    self.activityViewController = [[UIActivityViewController alloc]
                                   initWithActivityItems:@[self.textField.text]
                                   applicationActivities:nil];
    [self presentViewController:self.activityViewController
                       animated:YES
                     completion:^{
                         /* Nothing for now */
                     }];

}

Now if you run the app, enter some text in the text field, and then press the Share button, you will see something similar to Figure 1-28.

Sharing options displayed for the instance of string that we are trying to share

Figure 1-28. Sharing options displayed for the instance of string that we are trying to share

You can also have sharing options displayed as soon as your view controller is displayed on the screen. The viewDidAppear method of your view controller will be called when the view of your view controller is displayed on the screen and is guaranteed to be in the view hierarchy of your app, meaning that you can now display other views on top of your view controller’s view.

Warning

Do not attempt to present the activity view controller in the viewDidLoad method of your view controller. At that stage in the app, your view controller’s view is still not attached to the view hierarchy of the application, so attempting to present a view controller on the view will not work. Your view must be present in the hierarchy of the views for your modal views to work.

For this reason, you need to present the sharing view controller in the viewDidAppear method of your view controller.

See Also

Recipe 1.29

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