add page scroll

AmzPhoto/AmzPhoto/PagePhotos/PagePhotosDataSource.h

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+//
+//  PagePhotosDataSource.h
+//  PagePhotosDemo
+//
+//  Created by junmin liu on 10-8-23.
+//  Copyright 2010 Openlab. All rights reserved.
+//
+
+#import <UIKit/UIKit.h>
+
+
+@protocol PagePhotosDataSource
+
+// 有多少页
+//
+- (int)numberOfPages;
+
+// 每页的图片
+//
+- (UIImage *)imageAtIndex:(int)index;
+
+@end

AmzPhoto/AmzPhoto/PagePhotos/PagePhotosView.h

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+//
+//  PagePhotosView.h
+//  PagePhotosDemo
+//
+//  Created by junmin liu on 10-8-23.
+//  Copyright 2010 Openlab. All rights reserved.
+//
+
+#import <UIKit/UIKit.h>
+#import "PagePhotosDataSource.h"
+
+#define kPageScrollDone @"kPageScrollDone"
+
+@interface PagePhotosView : UIView<UIScrollViewDelegate> {
+	UIScrollView *scrollView;
+	UIPageControl *pageControl;
+
+	id<PagePhotosDataSource> dataSource;
+	NSMutableArray *imageViews;
+
+	// To be used when scrolls originate from the UIPageControl
+    BOOL pageControlUsed;
+}
+
+@property (nonatomic, assign) id<PagePhotosDataSource> dataSource;
+@property (nonatomic, retain) NSMutableArray *imageViews;
+
+- (IBAction)changePage:(id)sender;
+
+- (id)initWithFrame:(CGRect)frame withDataSource:(id<PagePhotosDataSource>)_dataSource;
+
+@end

AmzPhoto/AmzPhoto/PagePhotos/PagePhotosView.m

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+//
+//  PagePhotosView.m
+//  PagePhotosDemo
+//
+//  Created by junmin liu on 10-8-23.
+//  Copyright 2010 Openlab. All rights reserved.
+//
+
+#import "PagePhotosView.h"
+
+@interface PagePhotosView (PrivateMethods)
+
+- (void)loadScrollViewWithPage:(int)page;
+- (void)scrollViewDidScroll:(UIScrollView *)sender;
+
+@end
+
+@implementation PagePhotosView
+@synthesize dataSource;
+@synthesize imageViews;
+
+- (id)initWithFrame:(CGRect)frame withDataSource:(id<PagePhotosDataSource>)_dataSource {
+    if ((self = [super initWithFrame:frame])) {
+		self.dataSource = _dataSource;
+        // Initialization UIScrollView
+		int pageControlHeight = 20;
+		scrollView = [[UIScrollView alloc] initWithFrame:CGRectMake(0, 0, frame.size.width, frame.size.height - pageControlHeight)];
+		pageControl = [[UIPageControl alloc] initWithFrame:CGRectMake(0, frame.size.height - pageControlHeight, frame.size.width, pageControlHeight)];
+
+		[self addSubview:scrollView];
+		[self addSubview:pageControl];
+
+		int kNumberOfPages = [dataSource numberOfPages];
+
+		// in the meantime, load the array with placeholders which will be replaced on demand
+		NSMutableArray *views = [[NSMutableArray alloc] init];
+		for (unsigned i = 0; i < kNumberOfPages; i++) {
+			[views addObject:[NSNull null]];
+		}
+		self.imageViews = views;
+		[views release];
+
+		// a page is the width of the scroll view
+		scrollView.pagingEnabled = YES;
+		scrollView.contentSize = CGSizeMake(scrollView.frame.size.width * kNumberOfPages, scrollView.frame.size.height);
+		scrollView.showsHorizontalScrollIndicator = NO;
+		scrollView.showsVerticalScrollIndicator = NO;
+		scrollView.scrollsToTop = NO;
+		scrollView.delegate = self;
+
+		pageControl.numberOfPages = kNumberOfPages;
+		pageControl.currentPage = 0;
+		pageControl.backgroundColor = [UIColor blackColor];
+
+		// pages are created on demand
+		// load the visible page
+		// load the page on either side to avoid flashes when the user starts scrolling
+		[self loadScrollViewWithPage:0];
+		[self loadScrollViewWithPage:1];
+
+    }
+    return self;
+}
+
+
+- (void)loadScrollViewWithPage:(int)page {
+	int kNumberOfPages = [dataSource numberOfPages];
+
+    if (page < 0) return;
+    if (page >= kNumberOfPages) return;
+
+    // replace the placeholder if necessary
+    UIImageView *view = [imageViews objectAtIndex:page];
+    if ((NSNull *)view == [NSNull null]) {
+		UIImage *image = [dataSource imageAtIndex:page];
+        view = [[UIImageView alloc] initWithImage:image];
+        [imageViews replaceObjectAtIndex:page withObject:view];
+		[view release];
+    }
+
+    // add the controller's view to the scroll view
+    if (nil == view.superview) {
+        CGRect frame = scrollView.frame;
+        frame.origin.x = frame.size.width * page;
+        frame.origin.y = 0;
+        view.frame = frame;
+        [scrollView addSubview:view];
+    }
+}
+
+- (void)scrollViewDidScroll:(UIScrollView *)sender {
+    // We don't want a "feedback loop" between the UIPageControl and the scroll delegate in
+    // which a scroll event generated from the user hitting the page control triggers updates from
+    // the delegate method. We use a boolean to disable the delegate logic when the page control is used.
+    if (pageControlUsed) {
+        // do nothing - the scroll was initiated from the page control, not the user dragging
+        return;
+    }
+
+    // Switch the indicator when more than 50% of the previous/next page is visible
+    CGFloat pageWidth = scrollView.frame.size.width;
+    int page = floor((scrollView.contentOffset.x - pageWidth / 2) / pageWidth) + 1;
+    //time's up to quit
+    if(pageControl.currentPage==[dataSource numberOfPages]-1)
+    {
+        [[NSNotificationCenter defaultCenter]postNotificationName:kPageScrollDone object:nil];
+        return;
+    }
+    pageControl.currentPage = page;
+
+
+
+    // load the visible page and the page on either side of it (to avoid flashes when the user starts scrolling)
+    [self loadScrollViewWithPage:page - 1];
+    [self loadScrollViewWithPage:page];
+    [self loadScrollViewWithPage:page + 1];
+
+    // A possible optimization would be to unload the views+controllers which are no longer visible
+}
+
+// At the begin of scroll dragging, reset the boolean used when scrolls originate from the UIPageControl
+- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView {
+    pageControlUsed = NO;
+}
+
+// At the end of scroll animation, reset the boolean used when scrolls originate from the UIPageControl
+- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView {
+    pageControlUsed = NO;
+}
+
+- (IBAction)changePage:(id)sender {
+    int page = pageControl.currentPage;
+
+    // load the visible page and the page on either side of it (to avoid flashes when the user starts scrolling)
+    [self loadScrollViewWithPage:page - 1];
+    [self loadScrollViewWithPage:page];
+    [self loadScrollViewWithPage:page + 1];
+
+	// update the scroll view to the appropriate page
+    CGRect frame = scrollView.frame;
+    frame.origin.x = frame.size.width * page;
+    frame.origin.y = 0;
+    [scrollView scrollRectToVisible:frame animated:YES];
+
+	// Set the boolean used when scrolls originate from the UIPageControl. See scrollViewDidScroll: above.
+    pageControlUsed = YES;
+}
+
+
+- (void)dealloc {
+	[scrollView release];
+	[pageControl release];
+    [super dealloc];
+}
+
+
+@end