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

翻頁(yè)效果，類(lèi)似下面的樣子：

在電子書(shū)應(yīng)用中會(huì)很常見(jiàn)。這里需要兩個(gè)要點(diǎn)：

• 翻頁(yè)動(dòng)畫(huà)
• 手勢(shì)上下輕掃（swipe）的處理

先說(shuō)一下輕掃（swipe）的實(shí)現(xiàn)，可以參考 編寫(xiě)簡(jiǎn)單的手勢(shì)示例：Tap 了解手勢(shì)種類(lèi)。

在viewDidLoad方法中注冊(cè)了對(duì)上、下、左、右四個(gè)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(gè)方法，handleSwipeFrom。

在該方法中，再識(shí)別具體是哪個(gè)方向的輕掃手勢(shì)，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(guān)動(dòng)畫(huà)的處理，比如向下（往回）翻頁(yè)，類(lèi)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(yè)，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(shū)，還需要考慮一個(gè)問(wèn)題，就是有多個(gè)頁(yè)面（圖形），比如50頁(yè)。那么需要有一個(gè)數(shù)據(jù)結(jié)構(gòu)來(lái)保存這些頁(yè)面的圖片路徑：

• objc數(shù)據(jù)結(jié)構(gòu)，比如數(shù)組
• sqlite數(shù)據(jù)庫(kù)表

這樣，寫(xiě)一套翻頁(yè)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(shù)組，類(lèi)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(yè)下頁(yè)翻頁(yè)的時(shí)候找到關(guān)聯(lián)的頁(yè)面，采用了如下機(jī)制：

• 將圖片封裝為UIImageView顯示
• 可以為UIImageView設(shè)置一個(gè)tag值，值為數(shù)組下標(biāo)+1
• 這樣，上級(jí)view有方法能根據(jù)tag查詢(xún)到UIImageView，比如：UIView *currentView=[self.view viewWithTag:currentTag];
• 設(shè)置一個(gè)成員變量currentTag保存當(dāng)前的tag值

比如這樣，當(dāng)應(yīng)用加載的時(shí)候顯示第一頁(yè)：

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(yè)時(shí)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(xiě)簡(jiǎn)單的翻頁(yè)效果