iPhone SDK - Simple Slideshow

Your interface.




#import <UIKit/UIKit.h>

@interface ViewSlider : UIViewController {

    NSMutableArray *_pageViews;
    UIScrollView *_scrollView;
    NSUInteger _currentPageIndex;
    BOOL _rotationInProgress;
    
    int  m_itotalPages;
}

-(void)unloadPages;
- (CGSize)pageSize;
- (void)loadScrollView;
- (NSUInteger)numberOfPages;
- (void)currentPageIndexDidChange;
- (void)layoutPage:(NSUInteger)pageIndex;
- (BOOL)isPageLoaded:(NSUInteger)pageIndex;
- (UIView *)viewForPage:(NSUInteger)pageIndex;
- (UIView *)loadViewForPage:(NSUInteger)pageIndex;
- (CGRect)alignView:(UIView *)view forPage:(NSUInteger)pageIndex;

@end




Here is the implementation


pragma mark -

@interface ViewSlider () <UIScrollViewDelegate>

@property (nonatomic, retain) NSMutableArray *pageViews;
@property (nonatomic, retain) UIScrollView *scrollView;
@property (nonatomic, readonly) NSUInteger currentPageIndex;

@end

#pragma mark -

@implementation ViewSlider

#pragma mark -

@synthesize pageViews=_pageViews, scrollView=_scrollView, currentPageIndex=_currentPageIndex;


#pragma mark -

- (void)viewDidLoad {

    m_itotalPages=//set number of views ;

    //to initialize Scrollview 
    [self loadScrollView];
    
    self.pageViews = [NSMutableArray array];
    // to save time and memory, we won't load the page views immediately
    for (NSUInteger i = 0; i < m_itotalPages; ++i)
        [self.pageViews addObject:[NSNull null]];
}

- (void)viewWillAppear:(BOOL)animated {
    
    if(m_itotalPages !=0)    {
        
        _currentPageIndex=0;
        [self currentPageIndexDidChange];
        self.scrollView.contentOffset = CGPointMake(_currentPageIndex * [self pageSize].width, 0);
    }
}

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation {
    return UIDeviceOrientationIsPortrait(interfaceOrientation)||UIDeviceOrientationIsLandscape(interfaceOrientation);
}

- (void)willRotateToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation duration:(NSTimeInterval)duration {

    _rotationInProgress = YES;
    
    //to remove all views for memory managment
    [self unloadPages];
    [[self.scrollView subviews] makeObjectsPerformSelector:@selector(removeFromSuperview)];
    [[self.scrollView subviews] makeObjectsPerformSelector:@selector(release)];
    [self.pageViews removeAllObjects];
    
    for (NSUInteger i = 0; i < m_itotalPages; ++i)
        [self.pageViews addObject:[NSNull null]];
    
    //to load page views
    [self currentPageIndexDidChange];
    
    // hide other page views because they may overlap the current page during animation
    for (NSUInteger pageIndex = 0; pageIndex < [self numberOfPages]; ++pageIndex)
        if ([self isPageLoaded:pageIndex])
            [self viewForPage:pageIndex].hidden = (pageIndex != _currentPageIndex);
}

- (void)willAnimateRotationToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation duration:(NSTimeInterval)duration {
    // resize and reposition the page view, but use the current contentOffset as page origin
    // (note that the scrollview has already been resized by the time this method is called)

    UIView *pageView = [self viewForPage:_currentPageIndex];
    [self viewForPage:_currentPageIndex].frame = [self alignView:pageView forPage:_currentPageIndex];
}

- (void)didRotateFromInterfaceOrientation:(UIInterfaceOrientation)fromInterfaceOrientation {
    
    self.scrollView.contentMode=UIViewContentModeScaleAspectFill;
    self.scrollView.contentOffset = CGPointMake(_currentPageIndex * [self pageSize].width,0);
    
    // unhide
    for (NSUInteger pageIndex = 0; pageIndex < [self numberOfPages]; ++pageIndex)
        if ([self isPageLoaded:pageIndex])
            [self viewForPage:pageIndex].hidden = NO;
    
    _rotationInProgress = NO;
}


#pragma mark -
#pragma mark View methods

/**************************************************************************************
/*  Method Name    : loadScrollView
/*  Purpose        : to load Scrollview
/*  Parameters     : nil
/*  Return Value   : void
/***************************************************************************************/

- (void)loadScrollView {
    
    self.scrollView = [[[UIScrollView alloc] init] autorelease];
    self.scrollView.delegate = self;
    self.scrollView.pagingEnabled = YES;
    self.scrollView.showsHorizontalScrollIndicator = NO;
    self.scrollView.showsVerticalScrollIndicator = NO;
    self.scrollView.bounces=NO;
    self.scrollView.frame=self.view.frame;
    self.scrollView.contentMode=UIViewContentModeScaleAspectFill;
    self.view = self.scrollView;
}

#pragma mark -


- (void)layoutPage:(NSUInteger)pageIndex {
    @try {

        UIView *pageView = [self viewForPage:pageIndex];
        pageView.contentMode=UIViewContentModeScaleAspectFill;
        pageView.frame = [self alignView:pageView forPage:pageIndex]; 
    }
    @catch (NSException *e) {
        //NSLog(@"layoutPages");
    }
}

- (CGRect)alignView:(UIView *)view forPage:(NSUInteger)pageIndex {
    
        CGSize pageSize = [self pageSize];
        self.scrollView.frame=CGRectMake(0,  0, pageSize.width,pageSize.height);
        self.scrollView.contentSize=CGSizeMake(([self numberOfPages]*pageSize.width), pageSize.height);
    return CGRectMake(pageIndex * pageSize.width,0,pageSize.width,pageSize.height);
}

#pragma mark -

- (NSUInteger)numberOfPages {

    return m_itotalPages;
}

- (CGSize)pageSize {
    
        return CGSizeMake(768,1024);
}

- (BOOL)isPageLoaded:(NSUInteger)pageIndex {
    return [self.pageViews objectAtIndex:pageIndex] != [NSNull null];
}

- (UIView *)loadViewForPage:(NSUInteger)pageIndex {
    
    UIView *controller=[[UIView alloc] init];
    controller.backgroundColor=[UIColor blueColor];
    return controller;
}

- (UIView *)viewForPage:(NSUInteger)pageIndex {

    NSParameterAssert(pageIndex >= 0);
    NSParameterAssert(pageIndex < [self numberOfPages]);
    
    UIView *pageView;
    @try{
    
        if ([self.pageViews objectAtIndex:pageIndex] == [NSNull null]) {
        
            pageView = [self loadViewForPage:pageIndex];
            [self.pageViews replaceObjectAtIndex:pageIndex withObject:pageView];
            [self.scrollView addSubview:pageView];
            [pageView release];

        } else {
        
            pageView = [self.pageViews objectAtIndex:pageIndex];
        }
    }
    @catch (NSException *e) {
        //NSLog(@"Exception viewForPage");
    }
    return pageView;
}

- (void)currentPageIndexDidChange {
    @try{
        
        [self layoutPage:_currentPageIndex];
        if (_currentPageIndex+1 < [self numberOfPages])
            [self layoutPage:_currentPageIndex+1];
        if (_currentPageIndex > 0)
            [self layoutPage:_currentPageIndex-1];
        
        [self unloadPages];
        
        self.navigationItem.title = [NSString stringWithFormat:@"Page %d of %d", 1+_currentPageIndex, [self numberOfPages]];
    }
    @catch (NSException * e) {
        //NSLog(@"currentPageIndexDidChange");
    }
}

-(void)unloadPages    {
    
    @try {
    
        if (self.pageViews) {
            
            // unload non-visible pages in case the memory is scarse
            for (NSUInteger pageIndex = 0; pageIndex < [self numberOfPages]; ++pageIndex)    {
                if (pageIndex < _currentPageIndex-1 || pageIndex > _currentPageIndex+1)
                    if ([self isPageLoaded:pageIndex]) {
                        if(pageIndex==0 || pageIndex ==1)
                            continue;
                        
                        UIView *pageView = [self.pageViews objectAtIndex:pageIndex];

                        [[pageView subviews] makeObjectsPerformSelector:@selector(removeFromSuperview)];
                        [pageView removeFromSuperview];
                        if(pageView)    
                            pageView=nil;
                        [self.pageViews replaceObjectAtIndex:pageIndex withObject:[NSNull null]];
                    }    
            }
        }

    }
    @catch (NSException * e) {
        //NSLog(@"Exception Unload");
    }
    @finally {
        
    }
}

#pragma mark -

- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
    
    @try {

    if (_rotationInProgress)
        return; // UIScrollView layoutSubviews code adjusts contentOffset, breaking our logic
        
        CGSize pageSize = [self pageSize];
        NSUInteger newPageIndex = (self.scrollView.contentOffset.x + pageSize.width / 2) / pageSize.width;
        if (newPageIndex == _currentPageIndex) return;
    
        // could happen when scrolling fast
        if (newPageIndex < 0)
            newPageIndex = 0;
        else if (newPageIndex >= [self numberOfPages])
            newPageIndex = [self numberOfPages] - 1;
    
        _currentPageIndex = newPageIndex;
        [self currentPageIndexDidChange];

    }
    @catch (NSException * e) {
        //NSLog(@"DIDSCROLL");
    }
}

#pragma mark -
#pragma mark View Destructors

- (void)didReceiveMemoryWarning {
    
    [super didReceiveMemoryWarning];
    [self unloadPages];
}

- (void)viewDidUnload {
    self.pageViews = nil;
    self.scrollView = nil;
}

- (void)dealloc {
    
    [[self.scrollView subviews] makeObjectsPerformSelector:@selector(removeFromSuperview)];
    self.scrollView=nil;
    
    [self.pageViews removeAllObjects];
    [self.pageViews release];
    self.pageViews=nil;
    
    [self viewDidUnload];
    [super dealloc];
}

@end