一、引言

UIPageViewController是iOS中少見的動畫視圖控制器之一，通過它既可以創(chuàng)建類似UIScrollView與UIPageControl結(jié)合的滾屏視圖，也可以創(chuàng)建類似圖書效果的炫酷翻頁視圖。

UIPageViewController在iOS 5 SDK中首次引入，它使得開發(fā)者可以使用這個ViewController創(chuàng)建分頁視圖。在iOS 6中，這個類有了更新，支持滾動過渡效果。使用Page View，用戶可以方便的通過手勢在多個頁面之間導(dǎo)航。UIPageViewController并不僅僅用于引導(dǎo)頁，很多游戲，例如：憤怒的小鳥，就是用Page View來展示關(guān)卡選擇的頁面，還有有關(guān)書籍的應(yīng)用，用這個類來顯示書的頁面。
UIPageViewController是個高度可配置的類，你可以進行如下配置：

• 分頁的方向——水平或垂直
• 翻頁的樣式——書卷翻頁或者滑動翻頁
• 書脊位置——只有書卷翻頁樣式有效
• 頁面間距——只有滑動翻頁樣式有效，用來定義頁面間距（inter-page spacing）

UIPageViewController類似一個視圖容器，其中每個具體的視圖由各自的ViewController進行維護管理，UIPageViewController只進行協(xié)調(diào)與動畫布置。下圖可以很好的展現(xiàn)出UIPageViewControlelr的使用結(jié)構(gòu)：

上圖中，UIPageViewControllerDataSource協(xié)議為UIPageViewController提供數(shù)據(jù)支持，DataSource協(xié)議提供的數(shù)據(jù)來自各個ViewContoller自行維護，UIPageViewControllerDelegate中的回調(diào)可以對翻頁動作，屏幕旋轉(zhuǎn)動作等進行監(jiān)聽。UIPageViewController把從DataSource中獲取到的視圖數(shù)據(jù)渲染給View用于當(dāng)前視圖控制器的展示。

為了演示，我們會一起創(chuàng)建一個簡單的app。當(dāng)然，我們不會演示所有的UIPageViewController的配置細節(jié)，我們會演示到使用滑動翻頁樣式來創(chuàng)建一個引導(dǎo)頁。不過別擔(dān)心，有了對UIPageViewController的基本理解，我相信你能夠去探索其他的特性。

開始吧！

二、創(chuàng)建一個UIPageViewController

首先新建一個類作為翻頁視圖控制器中具體每一頁視圖的控制器，使其繼承于UIViewController：

ModelViewController.h

#import <UIKit/UIKit.h>
@interface ModelViewController : UIViewController
+(ModelViewController *)creatWithIndex:(int)index;
@property(nonatomic,strong)UILabel * indexLabel;
@end
ModelViewController.m

#import "ModelViewController.h"
@interface ModelViewController ()
@end
@implementation ModelViewController
+(ModelViewController *)creatWithIndex:(int)index{
    ModelViewController * con = [[ModelViewController alloc]init];
    con.indexLabel = [[UILabel alloc]initWithFrame:CGRectMake(110, 200, 100, 30)];
    con.indexLabel.text = [NSString stringWithFormat:@"第%d頁",index];
    [con.view addSubview:con.indexLabel];
    return con;
}
- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    self.view.backgroundColor = [UIColor redColor];
}
@end
在工程模板自帶的ViewController.m文件中實現(xiàn)如下代碼：

#import "ViewController.h"
#import "ModelViewController.h"
//遵守協(xié)議
@interface ViewController ()<UIPageViewControllerDataSource,UIPageViewControllerDelegate>
{
    //翻頁視圖控制器對象
    UIPageViewController * _pageViewControl;
    //數(shù)據(jù)源數(shù)組
    NSMutableArray * _dataArray;
}
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    //進行初始化
    _pageViewControl = [[UIPageViewController alloc]initWithTransitionStyle:UIPageViewControllerTransitionStyleScroll navigationOrientation:UIPageViewControllerNavigationOrientationHorizontal options:@{UIPageViewControllerOptionSpineLocationKey:@0,UIPageViewControllerOptionInterPageSpacingKey:@10}];
    self.view.backgroundColor = [UIColor greenColor];
    //設(shè)置翻頁視圖的尺寸
    _pageViewControl.view.bounds=self.view.bounds;
    //設(shè)置數(shù)據(jù)源與代理
    _pageViewControl.dataSource=self;
    _pageViewControl.delegate=self;
    //創(chuàng)建初始界面
    ModelViewController * model = [ModelViewController creatWithIndex:1];
    //設(shè)置初始界面
    [_pageViewControl setViewControllers:@[model] direction:UIPageViewControllerNavigationDirectionReverse animated:YES completion:nil];
    //設(shè)置是否雙面展示
    _pageViewControl.doubleSided = NO;
    _dataArray = [[NSMutableArray alloc]init];
    [_dataArray addObject:model];
    [self.view addSubview:_pageViewControl.view];
}
//翻頁控制器進行向前翻頁動作 這個數(shù)據(jù)源方法返回的視圖控制器為要顯示視圖的視圖控制器
- (nullable UIViewController *)pageViewController:(UIPageViewController *)pageViewController viewControllerBeforeViewController:(UIViewController *)viewController{
    int index = (int)[_dataArray indexOfObject:viewController];
    if (index==0) {
        return nil;
    }else{
        return _dataArray[index-1];
    }
}
//翻頁控制器進行向后翻頁動作 這個數(shù)據(jù)源方法返回的視圖控制器為要顯示視圖的視圖控制器
- (nullable UIViewController *)pageViewController:(UIPageViewController *)pageViewController viewControllerAfterViewController:(UIViewController *)viewController{
    int index = (int)[_dataArray indexOfObject:viewController];
    if (index==9) {
        return nil;
    }else{
        if (_dataArray.count-1>=(index+1)) {
            return _dataArray[index+1];
        }else{
            ModelViewController * model = [ModelViewController creatWithIndex:index+2];
            [_dataArray addObject:model];
            return model;
        }
    }
}
//屏幕旋轉(zhuǎn)觸發(fā)的代理方法
- (UIPageViewControllerSpineLocation) pageViewController:(UIPageViewController *)pageViewController spineLocationForInterfaceOrientation:(UIInterfaceOrientation)orientation{
    return UIPageViewControllerSpineLocationMin;
}
//設(shè)置分頁控制器的分頁數(shù)
- (NSInteger)presentationCountForPageViewController:(UIPageViewController *)pageViewController {
   
    return 10;
}
//設(shè)置初始的分頁點
- (NSInteger)presentationIndexForPageViewController:(UIPageViewController *)pageViewController{
    return 0;
}
@end
上面創(chuàng)建了最簡單的翻頁視圖控制器示例，效果如下圖：

三、UIPageViewController中方法使用解析

//創(chuàng)建翻頁視圖控制器對象
- (instancetype)initWithTransitionStyle:(UIPageViewControllerTransitionStyle)style navigationOrientation:(UIPageViewControllerNavigationOrientation)navigationOrientation options:(nullable NSDictionary<NSString *, id> *)options;
上面方法用于創(chuàng)建視圖控制器對象，其中UIPageViewControllerTransitionStyle參數(shù)設(shè)置翻頁控制器的風(fēng)格，枚舉如下：

typedef NS_ENUM(NSInteger, UIPageViewControllerTransitionStyle) {
    UIPageViewControllerTransitionStylePageCurl = 0, //類似于書本翻頁效果
    UIPageViewControllerTransitionStyleScroll = 1 // 類似于ScrollView的滑動效果
};
如果設(shè)置為UIPageViewControllerTransitionStyleCurl，翻頁效果如下圖所示：

上面初始化方法中的UIPageViewControllerNavigationOrientation屬性設(shè)置翻頁的方向，枚舉如下：

typedef NS_ENUM(NSInteger, UIPageViewControllerNavigationOrientation) {
    UIPageViewControllerNavigationOrientationHorizontal = 0,//水平翻頁
    UIPageViewControllerNavigationOrientationVertical = 1//豎直翻頁
};
options參數(shù)用于設(shè)置翻頁視圖控制器的配置字典，其可以設(shè)置的配置鍵值如下：

//這個鍵需要設(shè)置為UIPageViewControllerOptionSpineLocationKey枚舉值對應(yīng)的NSNumber對象 設(shè)置翻頁控制器的書軸 后面會介紹
NSString * const UIPageViewControllerOptionSpineLocationKey;
//這個鍵需要設(shè)置為NSNumber類型 設(shè)置每頁視圖的間距 用于滾動視圖風(fēng)格的
NSString * const UIPageViewControllerOptionInterPageSpacingKey;
下面是UIPageViewController的一些常用屬性與方法：

//設(shè)置數(shù)據(jù)源
@property (nullable, nonatomic, weak) id <UIPageViewControllerDelegate> delegate;
//設(shè)置代理
@property (nullable, nonatomic, weak) id <UIPageViewControllerDataSource> dataSource;
//獲取翻頁風(fēng)格
@property (nonatomic, readonly) UIPageViewControllerTransitionStyle transitionStyle;
//獲取翻頁方向
@property (nonatomic, readonly) UIPageViewControllerNavigationOrientation navigationOrientation;
//獲取書軸類型
@property (nonatomic, readonly) UIPageViewControllerSpineLocation spineLocation;
//設(shè)置是否雙面顯示
@property (nonatomic, getter=isDoubleSided) BOOL doubleSided;
//設(shè)置要顯示的視圖控制器
- (void)setViewControllers:(nullable NSArray<UIViewController *> *)viewControllers direction:(UIPageViewControllerNavigationDirection)direction animated:(BOOL)animated completion:(void (^ __nullable)(BOOL finished))completion;
上面只有spineLocation屬性有些難于理解，其枚舉如下：

typedef NS_ENUM(NSInteger, UIPageViewControllerSpineLocation) {
    //對于SCrollView類型的滑動效果 沒有書軸 會返回下面這個枚舉值
    UIPageViewControllerSpineLocationNone = 0,
    //以左邊或者上邊為軸進行翻轉(zhuǎn) 界面同一時間只顯示一個View
    UIPageViewControllerSpineLocationMin = 1, 
    //以中間為軸進行翻轉(zhuǎn) 界面同時可以顯示兩個View
    UIPageViewControllerSpineLocationMid = 2,
    //以下邊或者右邊為軸進行翻轉(zhuǎn) 界面同一時間只顯示一個View
    UIPageViewControllerSpineLocationMax = 3  
};
將上面的示例代碼修改幾個地方如下：

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    _pageViewControl = [[UIPageViewController alloc]initWithTransitionStyle:UIPageViewControllerTransitionStylePageCurl navigationOrientation:UIPageViewControllerNavigationOrientationVertical options:@{UIPageViewControllerOptionSpineLocationKey:@2,UIPageViewControllerOptionInterPageSpacingKey:@10}];
    self.view.backgroundColor = [UIColor greenColor];
    _pageViewControl.view.bounds=self.view.bounds;
    _pageViewControl.dataSource=self;
    _pageViewControl.delegate=self;
    ModelViewController * model = [ModelViewController creatWithIndex:1];
    ModelViewController * model2 = [ModelViewController creatWithIndex:2];
    [_pageViewControl setViewControllers:@[model,model2] direction:UIPageViewControllerNavigationDirectionReverse animated:YES completion:nil];
    _pageViewControl.doubleSided = YES;
    _dataArray = [[NSMutableArray alloc]init];
    [_dataArray addObject:model];
    [self.view addSubview:_pageViewControl.view];
}
- (UIPageViewControllerSpineLocation) pageViewController:(UIPageViewController *)pageViewController spineLocationForInterfaceOrientation:(UIInterfaceOrientation)orientation{
    return UIPageViewControllerSpineLocationMid;
}
運行效果如下圖所示：

四、UIPageViewControllerDataSource中方法解析

//向前翻頁展示的ViewController
- (nullable UIViewController *)pageViewController:(UIPageViewController *)pageViewController viewControllerBeforeViewController:(UIViewController *)viewController;
//向后翻頁展示的ViewController
- (nullable UIViewController *)pageViewController:(UIPageViewController *)pageViewController viewControllerAfterViewController:(UIViewController *)viewController;
//設(shè)置分頁控制器的分頁點數(shù)
- (NSInteger)presentationCountForPageViewController:(UIPageViewController *)pageViewController NS_AVAILABLE_IOS(6_0);
//設(shè)置當(dāng)前分頁控制器所高亮的點
- (NSInteger)presentationIndexForPageViewController:(UIPageViewController *)pageViewController NS_AVAILABLE_IOS(6_0);
五、UIPageViewControllerDelegate中方法解析

//翻頁視圖控制器將要翻頁時執(zhí)行的方法
- (void)pageViewController:(UIPageViewController *)pageViewController willTransitionToViewControllers:(NSArray<UIViewController *> *)pendingViewControllers NS_AVAILABLE_IOS(6_0);
//翻頁動畫執(zhí)行完成后回調(diào)的方法
- (void)pageViewController:(UIPageViewController *)pageViewController didFinishAnimating:(BOOL)finished previousViewControllers:(NSArray<UIViewController *> *)previousViewControllers transitionCompleted:(BOOL)completed;
//屏幕防線改變時回到的方法，可以通過返回值重設(shè)書軸類型枚舉
- (UIPageViewControllerSpineLocation)pageViewController:(UIPageViewController *)pageViewController spineLocationForInterfaceOrientation:(UIInterfaceOrientation)orientation;


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