Create a Cocoa application and name it Simple Slideshow.

Add the Quartz framework to the project.

For details, see Using the Image Kit in Xcode.

Choose File > New File.

Select “Objective-C NSWindowController subclass” and click Next.

Name the file SlideshowController.m and keep the option to create the header file. Then click Finish.

In the SlideshowController.h file, import the Quartz framework by adding this statement:

#import <Quartz/Quartz.h>

Add an instance variable for the slideshow and a mutable array for image paths.

The interface should look as follows:

@interface SlideshowController : NSWindowController {

    IKSlideshow        *mSlideshow;

    NSMutableArray *mImagePaths;

}

@end

Save the SlideshowController.h file.

Open the SlideshowController.m file.

In the implementation file, add an awakeFromNib method.

The method first obtains a shared instance of the slideshow. Next it loads images. You’ll write the loadImages method and its supporting methods later on. The loadImages method, if successful, will add image paths to the mImagePaths array. If paths are added, then the awakeFromNib method runs the slideshow, using the paths as the data source.

The following awakeFromNib method sets the mode to images only. If there are PDF documents in any folders that you add, Image Kit renders only the first page.

Note that the method does not set any options for the slideshow. However, you can set any of the options specified by the slideshow option key constants defined in IKSlideshow Class Reference.

- (void)awakeFromNib

{

     mSlideshow = [IKSlideshow sharedSlideshow];

     [self loadImages];

     if ([mImagePaths count] > 0)

        [mSlideshow runSlideshowWithDataSource:(id<IKSlideshowDataSource>)self

                      inMode: IKSlideshowModeImages

                      options: NULL];

}

Next you need to implement the two required methods of the IKSlideshowDataSource Protocol protocol.

The numberOfSlideshowItems method simply returns a count the number of paths in the mImagePaths array. The slideshowItemAtIndex: method returns the index of the mImagePaths array for the item in question.

- (NSUInteger)numberOfSlideshowItems

{

    return [mImagePaths count];

}

- (id)slideshowItemAtIndex: (NSUInteger)index

{

   int i;

   i = index % [mImagePaths count];

    return [mImagePaths objectAtIndex: i];

}

Implement a loadImages method.

This and the next few steps are where most of the work is done in the slideshow application. The loadImages method allocates and initializes the mImagePaths array, if necessary. Otherwise, the method removes all objects in preparation for adding new slideshow items.

Next the method calls a function to open files. You’ll write this routine in the next step. The openFiles routine invokes the Open panel (NSOpenPanel class) and returns an array of paths or NULL if the user cancels the Open panel. If there is an array of paths, the loadImages method iterates through the paths and calls the method addImagesFromPath:, which you’ll write in a moment.

- (void)loadImages

{

    if (NULL == mImagePaths)

    {

        mImagePaths = [[NSMutableArray alloc] init];

    } else {

      [mImagePaths removeAllObjects];

    }

    NSArray * array = openFiles();

    if (array != NULL)

    {

        NSEnumerator *  enumerator;

        NSString *      path;

        enumerator = [array objectEnumerator];

        while (path = [enumerator nextObject])

        {

                [self addImagesFromPath: path];

        }

    }

}

Next you need to include an openFiles routine, which you’ll add in the SlideshowController.m file, but prior to the implementation statement.

The openFiles routine creates an instance of the NSOpenPanel class, sets up options to allow the user to choose directories as well as files, runs the panel, and returns either an array of the file names chosen by the user, or nil if the user clicks the Cancel button.

static NSArray *openFiles()

{

    NSOpenPanel *panel;

    panel = [NSOpenPanel openPanel];

    [panel setFloatingPanel:YES];

    [panel setCanChooseDirectories:YES];

    [panel setCanChooseFiles:NO];

    int i = [panel runModal];

    if(i == NSOKButton){

        return [panel URLs];

    }

        return nil;

}

Write the addImagesFromPath: method called by the loadImages method.

The first task for this method is to obtain an array of all the string objects contained in the given path. Then the method iterates through the string objects. If the string does not have a filename extension, then it represents a path. In this case the method calls itself to recursively resolve the path into individual items. If the string has an extension, then it represents an individual item that can be added to the image path array.

- (void)addImagesFromPath: (NSString *)path

{

   NSArray * array  = [[NSFileManager defaultManager]

                   directoryContentsAtPath: path];

    NSEnumerator *  enumerator;

    NSString *      imagePath;

    enumerator = [array objectEnumerator];

    while (imagePath = [enumerator nextObject])

    {

        if ([[[imagePath pathExtension] lowercaseString] isEqualToString: @""])

        {

             [self addImagesFromPath: [NSString stringWithFormat: @"%@/%@/",

                                       path, imagePath]];

      } else

        {

            [mImagePaths addObject: [NSString stringWithFormat: @"%@/%@",

                                     path, imagePath]];

        }

    }

}

You need to write a choose images method that is invoked when the user chooses that command.

Recall that the user can stop a slideshow and start another by choosing File > Choose Images. You’ll add this menu item and connect to this action later on.

This method first calls the loadImages method to fetch and add new slideshow items. If there are items to add (that is, the user did not click Cancel in the Open panel), the method reloads the slideshow data and then runs the slideshow.

- (IBAction) chooseImages:(id) sender

{

    [self loadImages];

    if ([mImagePaths count] > 0) {

        [mSlideshow reloadData];

        [mSlideshow  runSlideshowWithDataSource: (id<IKSlideshowDataSource>)self

            inMode: IKSlideshowModeImages

            options: NULL];

    }

}

Save the SlideshowController.m file.

Open the SlideshowController.h file and add these method declarations:

- (IBAction)chooseImages:(id)sender;

- (NSUInteger)numberOfSlideshowItems;

- (id)slideshowItemAtIndex: (NSUInteger)index;

- (void)loadImages;

Save the SlideshowController.h file.

Double-click the MainMenu.nib file to open Interface Builder.

Choose File > Synchronize With Xcode.

Delete the window icon in the nib document window.

Double-click the MainMenu icon in the nib document window.

Drag a Menu Item (NSMenuItem) from the Library to the File menu and name the item Choose Images.

Drag an Object (NSObject) from the Library to the nib document window.

In the Identity inspector, type SlideshowController in the Name field. THen select SlideshowController from the Class pop-up menu.

Control-drag from the Choose Images menu item to the SlideshowController and in the connections panel choose chooseImages:.

Save the nib file.

In Xcode, click Build and Go. Then test your application to make sure it works.

You might get warnings if you placed the methods into your file in the wrong order.

Check to make sure that you can run a slideshow. Exit the slideshow, and then start another by choosing File > Choose Images.