编撰简单的翻页效果

编写简单的翻页效果

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

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页效果，类似下面的样子：

在电子书应用中会很常见。这里需要两个要点：在电子书应用中会很常见。这里需要两个要点：

翻页动画手势上下轻扫（swipe）的处理

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先说一下轻扫（swipe）的实现，可以参考编写简单的手势示例：Tap了解手势种类。

在viewDidLoad方法中注册了对上、下、左、右四个方向轻松的处理方法：

- (void)viewDidLoad {?
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??? UISwipeGestureRecognizer *recognizer;?
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??? recognizer = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:@selector(handleSwipeFrom:)];?
??? [recognizer setDirection:(UISwipeGestureRecognizerDirectionRight)];?
??? [[self view] addGestureRecognizer:recognizer];?
??? [recognizer release];?
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??? recognizer = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:@selector(handleSwipeFrom:)];?
??? [recognizer setDirection:(UISwipeGestureRecognizerDirectionUp)];?
??? [[self view] addGestureRecognizer:recognizer];?
??? [recognizer release];?
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??? recognizer = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:@selector(handleSwipeFrom:)];?
??? [recognizer setDirection:(UISwipeGestureRecognizerDirectionDown)];
??? [[self view] addGestureRecognizer:recognizer];?
??? [recognizer release];?
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??? recognizer = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:@selector(handleSwipeFrom:)];?
??? [recognizer setDirection:(UISwipeGestureRecognizerDirectionLeft)];?
??? [[self view] addGestureRecognizer:recognizer];?
??? [recognizer release];?
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??? [super viewDidLoad];

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可以看到，都是同一个方法，handleSwipeFrom。

在该方法中，再识别具体是哪个方向的轻扫手势，比如判断是向下的轻扫：

-(void)handleSwipeFrom:(UISwipeGestureRecognizer *)recognizer {?
??? NSLog(@"Swipe received.");?
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??? if (recognizer.direction==UISwipeGestureRecognizerDirectionDown) {?
??????? NSLog(@"swipe down");

判断是向上的轻扫：

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

有关动画的处理，比如向下（往回）翻页，类似这样：

[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）翻页，只需改为：

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

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

[UIView commitAnimations];

如果是电子书，还需要考虑一个问题，就是有多个页面（图形），比如50页。那么需要有一个数据结构来保存这些页面的图片路径：

objc数据结构，比如数组sqlite数据库表

这样，写一套翻页代码和加载什么图形之间就可以解耦。

本文示例使用的是数组，类似这样：

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

图片保存在resources下。

为了能让上页下页翻页的时候找到关联的页面，采用了如下机制：

将图片封装为UIImageView显示可以为UIImageView设置一个tag值，值为数组下标+1这样，上级view有方法能根据tag查询到UIImageView，比如：UIView *currentView=[self.view viewWithTag:currentTag];设置一个成员变量currentTag保存当前的tag值

比如这样，当应用加载的时候显示第一页：

??? currentTag=1;?
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??? NSString *path = [[NSBundle mainBundle] pathForResource:@"pageflip1" ofType:@"mp3"];?
??? player=[[AVAudioPlayer alloc] initWithContentsOfURL:[NSURL fileURLWithPath:path] error:NULL];?
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??? //[[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;

在翻页时的处理：

if (currentTag<[pages count]) {?
??? UIView *currentView=[self.view viewWithTag:currentTag];?
??? currentTag++;?
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??? UIImageView *contentView = [[UIImageView alloc] initWithFrame:[[UIScreen mainScreen] applicationFrame]];?
??? [contentView setImage:[UIImage imageNamed:[pages objectAtIndex:(currentTag-1)]]];??
??? [contentView setUserInteractionEnabled:YES];?
??? contentView.tag=currentTag;?
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??? [UIView beginAnimations:@"animationID" context:nil];?
??? [UIView setAnimationDuration:0.7f];?
??? [UIView setAnimationCurve:UIViewAnimationCurveEaseInOut];?
??? [UIView setAnimationRepeatAutoreverses:NO];?
??? [UIView setAnimationTransition:UIViewAnimationTransitionCurlUp forView:self.view cache:YES];?
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??? [currentView removeFromSuperview];?
??? [self.view addSubview:contentView];?
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??? [UIView commitAnimations];

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