Initial files

Classes/PageLoopViewController.h

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+
+#import <UIKit/UIKit.h>
+
+@interface PageLoopViewController : UIViewController {
+	NSMutableArray *_pageViews;
+	UIScrollView *_scrollView;
+	NSUInteger _currentPageIndex;
+	NSUInteger _currentPhysicalPageIndex;
+	BOOL _pageLoopEnabled;
+	BOOL _rotationInProgress;
+}
+
+@end

Classes/PageLoopViewController.m

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+
+#import "PageLoopViewController.h"
+
+
+@interface PageLoopViewController () <UIScrollViewDelegate>
+
+@property (nonatomic, retain) NSMutableArray *pageViews;
+@property (nonatomic, retain) UIScrollView *scrollView;
+@property (nonatomic, readonly) NSUInteger currentPageIndex;
+@property (nonatomic) NSUInteger physicalPageIndex;
+
+- (NSUInteger)physicalPageForPage:(NSUInteger)page;
+- (NSUInteger)pageForPhysicalPage:(NSUInteger)physicalPage;
+
+@end
+
+
+@implementation PageLoopViewController
+
+@synthesize pageViews=_pageViews, scrollView=_scrollView, currentPageIndex=_currentPageIndex;
+
+- (UIView *)loadViewForPage:(NSUInteger)pageIndex {
+	UIImage *image = nil;
+	switch(pageIndex % 3) {
+		case 0: image = [UIImage imageNamed:@"image1.png"]; break;
+		case 1: image = [UIImage imageNamed:@"image2.png"]; break;
+		case 2: image = [UIImage imageNamed:@"image3.png"]; break;
+	}
+	UIImageView *pageView = [[[UIImageView alloc] initWithImage:image] autorelease];
+	pageView.contentMode = UIViewContentModeScaleToFill;
+	return pageView;
+}
+
+- (CGRect)alignView:(UIView *)view forPage:(NSUInteger)pageIndex inRect:(CGRect)rect {
+	UIImageView *imageView = (UIImageView *)view;
+	CGSize imageSize = imageView.image.size;
+	CGFloat ratioX = rect.size.width / imageSize.width, ratioY = rect.size.height / imageSize.height;
+	CGSize size = (ratioX < ratioY ?
+				   CGSizeMake(rect.size.width, ratioX * imageSize.height) :
+				   CGSizeMake(ratioY * imageSize.width, rect.size.height));
+	return CGRectMake(rect.origin.x + (rect.size.width - size.width) / 2,
+					  rect.origin.y + (rect.size.height - size.height) / 2,
+					  size.width, size.height);
+}
+
+- (NSUInteger)numberOfPages {
+	return 3;
+}
+
+- (UIView *)viewForPhysicalPage:(NSUInteger)pageIndex {
+	NSParameterAssert(pageIndex >= 0);
+	NSParameterAssert(pageIndex < [self.pageViews count]);
+
+	UIView *pageView;
+	if ([self.pageViews objectAtIndex:pageIndex] == [NSNull null]) {
+		pageView = [self loadViewForPage:pageIndex];
+		[self.pageViews replaceObjectAtIndex:pageIndex withObject:pageView];
+		[self.scrollView addSubview:pageView];
+		NSLog(@"View loaded for page %d", pageIndex);
+	} else {
+		pageView = [self.pageViews objectAtIndex:pageIndex];
+	}
+	return pageView;
+}
+
+- (CGSize)pageSize {
+	return self.scrollView.frame.size;
+}
+
+- (BOOL)isPhysicalPageLoaded:(NSUInteger)pageIndex {
+	return [self.pageViews objectAtIndex:pageIndex] != [NSNull null];
+}
+
+- (void)layoutPhysicalPage:(NSUInteger)pageIndex {
+	UIView *pageView = [self viewForPhysicalPage:pageIndex];
+	CGSize pageSize = [self pageSize];
+	pageView.frame = [self alignView:pageView forPage:[self pageForPhysicalPage:pageIndex] inRect:CGRectMake(pageIndex * pageSize.width, 0, pageSize.width, pageSize.height)];
+}
+
+- (void)loadView {
+	_pageLoopEnabled = YES;
+
+	self.scrollView = [[[UIScrollView alloc] init] autorelease];
+    CGRect rect = [[UIScreen mainScreen] applicationFrame];
+    self.scrollView.frame = rect;
+	self.scrollView.delegate = self;
+	self.scrollView.pagingEnabled = YES;
+	self.scrollView.showsHorizontalScrollIndicator = NO;
+	self.scrollView.showsVerticalScrollIndicator = NO;
+	self.view = self.scrollView;
+}
+
+- (void)viewDidLoad {
+	self.pageViews = [NSMutableArray array];
+	// to save time and memory, we won't load the page views immediately
+	NSUInteger numberOfPhysicalPages = (_pageLoopEnabled ? 3 * [self numberOfPages] : [self numberOfPages]);
+	for (NSUInteger i = 0; i < numberOfPhysicalPages; ++i)
+		[self.pageViews addObject:[NSNull null]];
+}
+
+- (void)currentPageIndexDidChange {
+	[self layoutPhysicalPage:_currentPhysicalPageIndex];
+	if (_currentPhysicalPageIndex+1 < [self.pageViews count])
+		[self layoutPhysicalPage:_currentPhysicalPageIndex+1];
+	if (_currentPhysicalPageIndex > 0)
+		[self layoutPhysicalPage:_currentPhysicalPageIndex-1];
+	self.navigationItem.title = [NSString stringWithFormat:@"%d of %d", 1+_currentPageIndex, [self numberOfPages]];
+}
+
+- (void)layoutPages {
+	CGSize pageSize = [self pageSize];
+	self.scrollView.contentSize = CGSizeMake([self.pageViews count] * pageSize.width, pageSize.height);
+	// move all visible pages to their places, because otherwise they may overlap
+	for (NSUInteger pageIndex = 0; pageIndex < [self.pageViews count]; ++pageIndex)
+		if ([self isPhysicalPageLoaded:pageIndex])
+			[self layoutPhysicalPage:pageIndex];
+}
+
+- (void)viewWillAppear:(BOOL)animated {
+	[self layoutPages];
+	[self currentPageIndexDidChange];
+	[self setPhysicalPageIndex:[self physicalPageForPage:_currentPageIndex]];
+}
+
+- (NSUInteger)physicalPageIndex {
+	CGSize pageSize = [self pageSize];
+	return (self.scrollView.contentOffset.x + pageSize.width / 2) / pageSize.width;
+}
+
+- (void)setPhysicalPageIndex:(NSUInteger)newIndex {
+	self.scrollView.contentOffset = CGPointMake(newIndex * [self pageSize].width, 0);
+}
+
+- (NSUInteger)physicalPageForPage:(NSUInteger)page {
+	NSParameterAssert(page < [self numberOfPages]);
+	return (_pageLoopEnabled ? page + [self numberOfPages] : page);
+}
+
+- (NSUInteger)pageForPhysicalPage:(NSUInteger)physicalPage {
+	if (_pageLoopEnabled) {
+		NSParameterAssert(physicalPage < 3 * [self numberOfPages]);
+		return physicalPage % [self numberOfPages];
+	} else {
+		NSParameterAssert(physicalPage < [self numberOfPages]);
+		return physicalPage;
+	} 
+}
+
+- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
+	if (_rotationInProgress)
+		return; // UIScrollView layoutSubviews code adjusts contentOffset, breaking our logic
+
+	NSUInteger newPageIndex = self.physicalPageIndex;
+	if (newPageIndex == _currentPhysicalPageIndex) return;
+	_currentPhysicalPageIndex = newPageIndex;
+	_currentPageIndex = [self pageForPhysicalPage:_currentPhysicalPageIndex];
+
+	[self currentPageIndexDidChange];
+}
+
+- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate {
+}
+
+- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView {
+	NSLog(@"scrollViewDidEndDecelerating");
+	NSUInteger physicalPage = self.physicalPageIndex;
+	NSUInteger properPage = [self physicalPageForPage:[self pageForPhysicalPage:physicalPage]];
+	if (physicalPage != properPage)
+		self.physicalPageIndex = properPage;
+}
+
+- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation {
+    return (interfaceOrientation != UIInterfaceOrientationPortraitUpsideDown);
+}
+
+- (void)willRotateToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation duration:(NSTimeInterval)duration {
+	_rotationInProgress = YES;
+
+	// hide other page views because they may overlap the current page during animation
+	for (NSUInteger pageIndex = 0; pageIndex < [self.pageViews count]; ++pageIndex)
+		if ([self isPhysicalPageLoaded:pageIndex])
+			[self viewForPhysicalPage:pageIndex].hidden = (pageIndex != _currentPhysicalPageIndex);
+}
+
+- (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)
+	CGSize pageSize = [self pageSize];
+	UIView *pageView = [self viewForPhysicalPage:_currentPhysicalPageIndex];
+	pageView.frame = [self alignView:pageView forPage:_currentPageIndex inRect:CGRectMake(self.scrollView.contentOffset.x, 0, pageSize.width, pageSize.height)];
+}
+
+- (void)didRotateFromInterfaceOrientation:(UIInterfaceOrientation)fromInterfaceOrientation {
+	// adjust frames according to the new page size - this does not cause any visible changes
+	[self layoutPages];
+	self.physicalPageIndex = _currentPhysicalPageIndex;
+
+	// unhide
+	for (NSUInteger pageIndex = 0; pageIndex < [self.pageViews count]; ++pageIndex)
+		if ([self isPhysicalPageLoaded:pageIndex])
+			[self viewForPhysicalPage:pageIndex].hidden = NO;
+
+	_rotationInProgress = NO;
+}
+
+- (void)didReceiveMemoryWarning {
+    [super didReceiveMemoryWarning];
+	if (self.pageViews) {
+		// unload non-visible pages in case the memory is scarse
+		for (NSUInteger pageIndex = 0; pageIndex < [self.pageViews count]; ++pageIndex)
+			if (pageIndex < _currentPhysicalPageIndex-1 || pageIndex > _currentPhysicalPageIndex+1)
+				if ([self isPhysicalPageLoaded:pageIndex]) {
+					UIView *pageView = [self.pageViews objectAtIndex:pageIndex];
+					[self.pageViews replaceObjectAtIndex:pageIndex withObject:[NSNull null]];
+					[pageView removeFromSuperview];
+				}
+	}
+}
+
+- (void)viewDidUnload {
+	self.pageViews = nil;
+	self.scrollView = nil;
+}
+
+- (void)dealloc {
+	[self viewDidUnload];
+    [super dealloc];
+}
+
+@end

Classes/ScrollerAppDelegate.h

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+//
+//  ScrollerAppDelegate.h
+//  Scroller
+//
+//  Created by Martin Volerich on 5/21/10.
+//  Copyright Bill Bear Technologies 2010. All rights reserved.
+//
+
+#import <UIKit/UIKit.h>
+
+@class PageLoopViewController;
+
+@interface ScrollerAppDelegate : NSObject <UIApplicationDelegate> {
+    UIWindow *window;
+    PageLoopViewController *viewController;
+}
+
+
+
+@end
+

Classes/ScrollerAppDelegate.m

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+//
+//  ScrollerAppDelegate.m
+//  Scroller
+//
+//  Created by Martin Volerich on 5/21/10.
+//  Copyright Bill Bear Technologies 2010. All rights reserved.
+//
+
+#import "ScrollerAppDelegate.h"
+#import "PageLoopViewController.h"
+
+@implementation ScrollerAppDelegate
+
+
+- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {    
+
+    viewController = [[PageLoopViewController alloc] init];
+
+    window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
+
+    // Override point for customization after app launch    
+    [window addSubview:viewController.view];
+    [window makeKeyAndVisible];
+
+	return YES;
+}
+
+
+- (void)dealloc {
+    [viewController release];
+    [window release];
+    [super dealloc];
+}
+
+
+@end

Scroller-Info.plist

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+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<key>CFBundleDevelopmentRegion</key>
+	<string>English</string>
+	<key>CFBundleDisplayName</key>
+	<string>${PRODUCT_NAME}</string>
+	<key>CFBundleExecutable</key>
+	<string>${EXECUTABLE_NAME}</string>
+	<key>CFBundleIconFile</key>
+	<string>ipadicon.png</string>
+	<key>CFBundleIdentifier</key>
+	<string>com.volerich.${PRODUCT_NAME:rfc1034identifier}</string>
+	<key>CFBundleInfoDictionaryVersion</key>
+	<string>6.0</string>
+	<key>CFBundleName</key>
+	<string>${PRODUCT_NAME}</string>
+	<key>CFBundlePackageType</key>
+	<string>APPL</string>
+	<key>CFBundleSignature</key>
+	<string>????</string>
+	<key>CFBundleVersion</key>
+	<string>1.0</string>
+	<key>LSRequiresIPhoneOS</key>
+	<true/>
+	<key>UISupportedInterfaceOrientations</key>
+	<array>
+		<string>UIInterfaceOrientationPortrait</string>
+		<string>UIInterfaceOrientationPortraitUpsideDown</string>
+		<string>UIInterfaceOrientationLandscapeLeft</string>
+		<string>UIInterfaceOrientationLandscapeRight</string>
+	</array>
+</dict>
+</plist>