点击UIButton后如何在UIPageViewController中添加新的视图控制器?

Question

我想知道如何实现会影响UIPageViewController模型的按钮。例如，我希望我的 UIPageViewController 模型数组加载其中的单个对象，当点击按钮时，将添加新的视图控制器，并将自动翻转页面或类似的东西(如在 Notes 应用程序中)。删除用户看到的当前对象也是如此。

到目前为止，我尝试在我的根视图控制器上实现一些 IBActions，但到目前为止没有运气。

以下是我实现视图控制器类的方法：

@implementation ViewController
@synthesize modelArray = _modelArray;
@synthesize pageVC = _pageVC;
#pragma mark - UIPageViewControllerDataSource Methods
// Returns the view controller before the given view controller. (required)
- (UIViewController *)pageViewController:(UIPageViewController *)pageViewController
viewControllerBeforeViewController:(UIViewController *)viewController
{
NSUInteger currentIndex = [self.modelArray indexOfObject:[(ContentVC *)viewController     labelContents]];
if(currentIndex==0)
return nil;
ContentVC *cVC = [[ContentVC alloc] init];
cVC.labelContents = [self.modelArray objectAtIndex:currentIndex-1];
return cVC;
}
// Returns the view controller after the given view controller. (required)
- (UIViewController *)pageViewController:(UIPageViewController *)pageViewController
viewControllerAfterViewController:(UIViewController *)viewController
{
NSUInteger currentIndex = [self.modelArray indexOfObject:[(ContentVC *)viewController labelContents]];
if(currentIndex==self.modelArray.count-1)
return nil;
ContentVC *cVC = [[ContentVC alloc] init];
cVC.labelContents = [self.modelArray objectAtIndex:currentIndex+1];
return cVC;
}
#pragma mark - UIPageViewControllerDelegate Methods
// Returns the spine location for the given orientation.
- (UIPageViewControllerSpineLocation)pageViewController:(UIPageViewController *)pageViewController
spineLocationForInterfaceOrientation:(UIInterfaceOrientation)orientation
{
if(UIInterfaceOrientationIsPortrait(orientation)){
// Set the array with only 1 view controller
UIViewController *currentVC = [self.pageVC.viewControllers objectAtIndex:0];
NSArray *viewControllers = [NSArray arrayWithObject:currentVC];
[self.pageVC setViewControllers:viewControllers direction:UIPageViewControllerNavigationDirectionForward animated:YES completion:nil];
// Set the doubleSided property to NO
self.pageVC.doubleSided = NO;
// Return the spine location
return UIPageViewControllerSpineLocationMin;
} else { // if landscape
NSArray *viewControllers = nil;
ContentVC *currentVC = [self.pageVC.viewControllers objectAtIndex:0];
NSUInteger currentIndex = [self.modelArray indexOfObject:[(ContentVC *)viewControllers labelContents]];
if(currentIndex==0 || currentIndex %2 == 0){
UIViewController *nextViewController = [self pageViewController:self.pageVC viewControllerAfterViewController:currentVC];
viewControllers = [NSArray arrayWithObjects:currentVC, nextViewController, nil];
} else {
UIViewController *previousVC = [self pageViewController:self.pageVC viewControllerBeforeViewController:currentVC];
viewControllers = [NSArray arrayWithObjects:previousVC, currentVC, nil];
}
// Set the view controllers as property of the UIPageViewController
[self.pageVC setViewControllers:viewControllers direction:UIPageViewControllerNavigationDirectionForward animated:YES completion:nil];
return UIPageViewControllerSpineLocationMid;
}
}
#pragma mark - View lifecycle
- (void)viewDidLoad
{
[super viewDidLoad];
// Instantiate the model array
self.modelArray = [[NSMutableArray alloc] init];
[self.modelArray addObject:@"Page One"];
NSLog(@"%@", self.modelArray);
// Instantiate the UIPageViewController
self.pageVC = [[UIPageViewController alloc] initWithTransitionStyle:UIPageViewControllerTransitionStyleScroll navigationOrientation:UIPageViewControllerNavigationOrientationHorizontal options:nil];
// Assign the delegate and datasource as self
self.pageVC.delegate = self;
self.pageVC.dataSource = self;
// Set the initial view controllers
ContentVC *cVC = [[ContentVC alloc] initWithNibName:@"ContentVC" bundle:nil];
cVC.labelContents = [self.modelArray objectAtIndex:0];
NSArray *viewControllers = [NSArray arrayWithObject:cVC];
[self.pageVC setViewControllers:viewControllers direction:UIPageViewControllerNavigationDirectionForward animated:NO completion:nil];
// Add the pageViewController as the childViewController
[self addChildViewController:self.pageVC];
// Add the view of pageViewController  to the currentView
[self.view addSubview:self.pageVC.view];
// Call didMoveToParentViewController: of the childViewController, the UIPageViewController instance in our case.
[self.pageVC didMoveToParentViewController:self];
// Assign the gestureRecognizers property of the pageViewController to the view's gestureRecognizers property
self.view.gestureRecognizers = self.pageVC.gestureRecognizers;
}

谢谢！

Answer 1

UIPageViewController使用数据源获取下一个或上一个视图控制器。因此，解决方案是在触摸按钮后将新的视图控制器添加到数据源。

假设您的数据源是作为NSArray实现的(有关此示例，请参阅 XCode 的基于页面的应用程序模板)，您只需将新的 vc 添加到该数组并通过调用[UIPageViewController setViewControllers:direction:animated:completion:]来设置新的 vc。

由于您没有提供有关如何实现层次结构的任何详细信息，因此我不能更具体。

编辑：

现在我有一些代码，这是我要做的：

首先，我不会保存labelContents，而是将视图控制器本身保存在modelArray中。除此之外，您当前的设计会在每次更改页面时创建一个新ContentVC。这是很多不必要的开销。以下是我将如何实现它：

(顺便说一句，你应该想一个比labelContents更具描述性的名字。现在，如果只有一个标签可能会很好，但是如果您将来添加更多标签怎么办？

- (ContentVC *)contentViewControllerWithLabelContents:(NSString *)labelContents
{
ContentVC *vc = [[ContentVC alloc] initWithNibName:@"ContentVC" bundle:nil];
vc.labelContents = labelContents;
return vc;
}
- (void)viewDidLoad
{
NSMutableArray *vcs = [NSMutableArray array];
[vcs addObject:[self contentViewControllerWithLabelContents:@"Page One"]];
[vcs addObject:[self contentViewControllerWithLabelContents:@"Page Two"]];
//...
self.modelArray = vcs;
}

#pragma mark - UIPageViewControllerDataSource Methods
// Returns the view controller before the given view controller. (required)
- (UIViewController *)pageViewController:(UIPageViewController *)pageViewController
viewControllerBeforeViewController:(UIViewController *)viewController
{
NSUInteger currentIndex = [self.modelArray indexOfObject:viewController];
if(currentIndex == 0)
return nil;
ContentVC *cVC = [self.modelArray objectAtIndex:currentIndex - 1];
return cVC;
}
// Returns the view controller after the given view controller. (required)
- (UIViewController *)pageViewController:(UIPageViewController *)pageViewController
viewControllerAfterViewController:(UIViewController *)viewController
{
NSUInteger currentIndex = [self.modelArray indexOfObject:viewController];
if(currentIndex == self.modelArray.count - 1)
return nil;
ContentVC *cVC = [self.modelArray objectAtIndex:currentIndex + 1];
return cVC;
}

您注释中的代码：

- (IBAction)newButtonTapped:(id)sender 
{ 
if(sender){ 
[self.modelArray addObject:@"Page Two"]; 
ContentVC *newVC = [[ContentVC alloc] initWithNibName:@"ContentVC" bundle:nil]; 
NSArray *arr = [NSArray arrayWithObject:newVC]; 
[self.pageVC setViewControllers:arr direction:UIPageViewControllerNavigationDirectionForward animated:NO completion:nil]; 
NSLog(@"%@", self.modelArray); 
} 
}

不起作用，因为您没有设置ContentVC的labelContents。所以你基本上最终会调用[self.modelObject indexOfObject:nil]或[self.modelObject indexOfObject:@""]，这取决于你对labelContents的实现。由于它们都不在数组中，因此调用返回NSNotFound在 64 位系统上将其转换为NSIntegerMax这就是2147483647。稍后您尝试在索引NSIntegerMax - 1处访问您的modelArray，这引发了一个NSRangeException。

因此，可以通过在newButtonTapped:方法中设置labelContents来解决此问题，或者如果您按照我的建议重新设计代码：

- (IBAction)newButtonTapped:(id)sender 
{ 
if(sender){ 
ContentVC *newVC = [self contentViewControllerWithLabelContents:@"Page Two"]; 
[self.modelArray addObject:newVC];
NSArray *newVCs = nil;
if (UIInterfaceOrientationIsPortrait(self.interfaceOrientation) || self.modelArray.count == 1)
newVCs = @[newVC];
else
{
NSUInteger secondLastIndex = self.modelArray.count - 2;
id previousVC = [self.modelArray objectAtIndex:secondLastIndex];
newVCs = @[previousVC, newVC];
}
[self.pageVC setViewControllers:newVCs direction:UIPageViewControllerNavigationDirectionForward animated:NO completion:nil];
} 
}