http://marshal.easymorse.com/archives/3760

翻頁效果，類似下面的樣子：

在電子書應用中會很常見。這里需要兩個要點：

• 翻頁動畫
• 手勢上下輕掃（swipe）的處理

先說一下輕掃（swipe）的實現，可以參考 編寫簡單的手勢示例：Tap 了解手勢種類。

在viewDidLoad方法中注冊了對上、下、左、右四個方向輕松的處理方法：

- (void)viewDidLoad {

UISwipeGestureRecognizer *recognizer;

recognizer = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:@selector(handleSwipeFrom:)];
[recognizer setDirection:(UISwipeGestureRecognizerDirectionRight)];
[[self view] addGestureRecognizer:recognizer];
[recognizer release];

recognizer = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:@selector(handleSwipeFrom:)];
[recognizer setDirection:(UISwipeGestureRecognizerDirectionUp)];
[[self view] addGestureRecognizer:recognizer];
[recognizer release];

recognizer = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:@selector(handleSwipeFrom:)];
[recognizer setDirection:(UISwipeGestureRecognizerDirectionDown)];
[[self view] addGestureRecognizer:recognizer];
[recognizer release];

recognizer = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:@selector(handleSwipeFrom:)];
[recognizer setDirection:(UISwipeGestureRecognizerDirectionLeft)];
[[self view] addGestureRecognizer:recognizer];
[recognizer release];


[super viewDidLoad];

可以看到，都是同一個方法，handleSwipeFrom。

在該方法中，再識別具體是哪個方向的輕掃手勢，比如判斷是向下的輕掃：

-(void)handleSwipeFrom:(UISwipeGestureRecognizer *)recognizer {
NSLog(@"Swipe received.");

if (recognizer.direction==UISwipeGestureRecognizerDirectionDown) {
NSLog(@"swipe down");

判斷是向上的輕掃：

if (recognizer.direction==UISwipeGestureRecognizerDirectionUp) {
NSLog(@"swipe up");

有關動畫的處理，比如向下（往回）翻頁，類似這樣：

[UIView beginAnimations:@"animationID" context:nil];
[UIView setAnimationDuration:0.7f];
[UIView setAnimationCurve:UIViewAnimationCurveEaseInOut];
[UIView setAnimationRepeatAutoreverses:NO];
[UIView setAnimationTransition:UIViewAnimationTransitionCurlDown forView:self.view cache:YES];

[currentView removeFromSuperview];
[self.view addSubview:contentView];

[UIView commitAnimations];

向上（向前）翻頁，只需改為：

[UIView beginAnimations:@"animationID" context:nil];
[UIView setAnimationDuration:0.7f];
[UIView setAnimationCurve:UIViewAnimationCurveEaseInOut];
[UIView setAnimationRepeatAutoreverses:NO];
[UIView setAnimationTransition: UIViewAnimationTransitionCurlUp forView:self.view cache:YES];

[currentView removeFromSuperview];
[self.view addSubview:contentView];

[UIView commitAnimations];

如果是電子書，還需要考慮一個問題，就是有多個頁面（圖形），比如50頁。那么需要有一個數據結構來保存這些頁面的圖片路徑：

• objc數據結構，比如數組
• sqlite數據庫表

這樣，寫一套翻頁代碼和加載什么圖形之間就可以解耦。

本文示例使用的是數組，類似這樣：

pages=[[NSArray alloc] initWithObjects:@"1.jpg",@"2.jpg",@"3.jpg",@"4.jpg",@"5.jpg",@"6.jpg",
nil];

圖片保存在resources下。

為了能讓上頁下頁翻頁的時候找到關聯的頁面，采用了如下機制：

• 將圖片封裝為UIImageView顯示
• 可以為UIImageView設置一個tag值，值為數組下標+1
• 這樣，上級view有方法能根據tag查詢到UIImageView，比如：UIView *currentView=[self.view viewWithTag:currentTag];
• 設置一個成員變量currentTag保存當前的tag值

比如這樣，當應用加載的時候顯示第一頁：

currentTag=1;

NSString *path = [[NSBundle mainBundle] pathForResource:@"pageflip1" ofType:@"mp3"];
player=[[AVAudioPlayer alloc] initWithContentsOfURL:[NSURL fileURLWithPath:path] error:NULL];

//[[UIApplication sharedApplication] setStatusBarHidden:YES animated:NO];
[[UIApplication sharedApplication] setStatusBarHidden:YES withAnimation: UIStatusBarAnimationSlide];
UIImageView *contentView = [[UIImageView alloc] initWithFrame:[[UIScreen mainScreen] applicationFrame]];
[contentView setImage:[UIImage imageNamed:[pages objectAtIndex:(currentTag-1)]]];
[contentView setUserInteractionEnabled:YES];
contentView.tag=currentTag;

在翻頁時的處理：

if (currentTag<[pages count]) {
UIView *currentView=[self.view viewWithTag:currentTag];
currentTag++;

UIImageView *contentView = [[UIImageView alloc] initWithFrame:[[UIScreen mainScreen] applicationFrame]];
[contentView setImage:[UIImage imageNamed:[pages objectAtIndex:(currentTag-1)]]];
[contentView setUserInteractionEnabled:YES];
contentView.tag=currentTag;

[UIView beginAnimations:@"animationID" context:nil];
[UIView setAnimationDuration:0.7f];
[UIView setAnimationCurve:UIViewAnimationCurveEaseInOut];
[UIView setAnimationRepeatAutoreverses:NO];
[UIView setAnimationTransition:UIViewAnimationTransitionCurlUp forView:self.view cache:YES];

[currentView removeFromSuperview];
[self.view addSubview:contentView];

[UIView commitAnimations];

編寫簡單的翻頁效果