Cloning UIImagePickerController using the Assets Library Framework

October 7th, 2010 Posted by: - posted under:Featured » Tutorials

Hello iCoders. This is a follow up post to my initial post on the Assets Library Framework and Blocks. We came across an interesting problem when working on the application for Animoto.com. They have had an app in the store since the very early days of the app store, and one of our biggest struggles has been creating an interface to allow users to select multiple photos from their photo album for a slideshow. While the iPhone photos application allows for this, the UIImagePicker does not. With the release of the Assets Library framework we can now recreate the experience of the UIImagePicker, with some additional custom functionality to fit our needs. As a result we created a new cloned version of the UIImagePicker that allows for multiple photo selection just like the photos app. We have decided to open source the controller for other developers to use. This post will explain the process of creating the new image picker as well as the method of incorporating it into your code.

The ELCImagePickerController

The ELCImagePickerController is only possible because of the newly introduced Assets Library framework. This framework gives you raw (more or less) access to the photo and video elements of a user. We looked at UIImagePickerController and saw a lot of weaknesses with it. You can only select 1 photo at a time, and even in Apple’s photo app, where you can choose several pictures at a time, you can’t use multi touch to do your selection. To solve these problems we rolled our own solution that works very closely to UIImagePickerController.

How to use it

First I am going to explain using the picker since to many people the process of creating it won’t be very interesting. The image picker is created and displayed in a very similar manner to the UIImagePickerController. The sample application that is part of the GitHub project, where I distribute the controller, shows its use, but I will go into detail here. To display the controller you instantiate it and display it modally like so.

ELCImagePickerController *controller = [[ELCImagePickerController alloc] initImagePicker];
[controller setDelegate:self];
[self presentModalViewController:controller animated:YES];
[controller release];

The ELCImagePickerController will return the select images back to the ELCImagePickerControllerDelegate. The delegate contains to methods very similar to the UIImagePickerControllerDelegate. Instead of returning one dictionary representing a single image the controller sends back an array of similarly structured dictionaries. The two delegate methods are:]

- (void)elcImagePickerController:(ELCImagePickerController *)picker didFinishPickingMediaWithInfo:(NSArray *)info;
- (void)elcImagePickerControllerDidCancel:(ELCImagePickerController *)picker;

GIT Hub

You can find this project now on GitHub. Please let me know any issues you may have and look for future releases with feature enhancements

General Structure

The ELCImagePicker is a collection of UITableViewControllers that are placed inside a UINavigationController. While the ELCImagePickerController is actually 5 separate custom classes I have written, I have put them all within a single header and main. I chose this to make the classes that were required to be imported into a project when using this as few as possible. While usually when presenting a UINavigationController you would create one yourself in code and use the initWithRootViewController method, in this case we have created a UINavigationController subclass called ELCImagePickerController which does all this behind the scenes. In the end all a developer has to do is use the initImagePicker method and present the controller modally. This lets the class match the functionality of UIImagePickerController closer. You can see the Header and Main for the ELCImagePickerController class on the next page.

ELCImagePickerControllerDemo from Collin Ruffenach on Vimeo.

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