在 UINavigationController 中控制向后滑动操作

Question

我正在创建一个简单的闪存卡应用程序，如下图所示：

我希望像这样向后滑动：

为此，onBack(index: Int) 是我需要在向后滑动时调用的名称（以更新显示的卡片）：

import UIKit

class ViewController: UIViewController {
    @IBOutlet weak var flashCardLabel: UILabel!

    // Populate initial content
    let content = ["Lorem", "Ipsum", "Dolor", "Sit"]

    // Index of where we are in content
    var index = 0

    override func viewDidLoad() {
        super.viewDidLoad()
    }

    // Label text based on index
    func setLabelToIndex() {
        flashCardLabel.text = content[index]
    }

    // Go back
    @IBAction func back(_ sender: Any) {
        if index > 0 {
            index = index - 1
            setLabelToIndex()
        }
    }

    // Go forward
    @IBAction func next(_ sender: Any) {
        if index + 1 < content.count {
            index = index + 1
            setLabelToIndex()
        }
    }

    // Desired function to be called
    // when swiping back in navigation stack
    func onBack(index: Int) {
        self.index = index
        setLabelToIndex()
    }
}

Answer 1

如果我正确理解您的问题，您希望能够在问题之间滑动和/或在单击“下一步”或“返回”时产生滑动效果。如果是这种情况，我建议您将UILabel 嵌入UIScrollView。看看这个：

class ViewController: UIViewController,UIScrollViewDelegate {

    let content = ["Lorem", "Ipsum", "Dolor", "Sit"]
    let scrollView = UIScrollView(frame: CGRect(x: 0, y: 0, width: 320, height: 300))

    var index = 0

    override func viewDidLoad() {
        super.viewDidLoad()

        scrollView.delegate = self        
        scrollView.contentSize = CGSize(width: self.view.frame.width * content.count, height: self.scrollView.frame.size.height)
        scrollView.isPagingEnabled = true

        // add labels to pages
        for i in 0 ..< content.count {
            let label = UILabel(frame: CGRect(x: self.view.center.x * (i + 1), y: self.view.center.y, width: 100, height: 50))
            label.textAlignment = .center
            label.text = content[i]
            scrollView.addSubview(label)
        }
        self.view.addSubview(scrollView)

    }

    // Go back
    @IBAction func back(_ sender: Any) {
        if index > 0 {
            index = index - 1

            // scroll to page
            let offset = CGPoint(x: CGFloat(index) * self.view.frame.width, y: 0)
            self.scrollView.setContentOffset(offset, animated: true)
        }
    }

    // Go forward
    @IBAction func next(_ sender: Any) {
        if index + 1 < content.count {
            index = index + 1

            // scroll to page
            let offset = CGPoint(x: CGFloat(index) * self.view.frame.width, y: 0)
            self.scrollView.setContentOffset(offset, animated: true)
        }
    }

    func scrollViewDidEndDecelerating(_ scrollView: UIScrollView) {
        index = round(scrollView.contentOffset.x / scrollView.frame.size.width)
    }
}

说明：

您基本上创建一个UIScrollView 来处理分页效果，并使用content 数组中的相应文本将UILabel 添加到每个页面。每次用户滚动到不同的页面时，index 都会更新为当前页面的索引。最后，当用户点击“下一页”或“后退”时，您会滚动到下一页或上一页

Answer 2

如果您希望通过 Push & Pop 导航控制器来实现，您可以通过设置静态索引变量来实现。 这是代码

class ViewController: UIViewController {


    @IBOutlet weak var flashCardLabel: UILabel!

    // Populate initial content
    let content = ["Lorem", "Ipsum", "Dolor", "Sit"]

    // Index of where we are in content
    static var INDEX = 0;

    override func viewDidLoad() {
        super.viewDidLoad()
        self.next(nil);
    }


    // Label text based on index
    func setLabelToIndex() {
        flashCardLabel.text = content[ViewController.INDEX]
    }

    // Go back
    @IBAction func back(_ sender: Any?) {
        if ViewController.INDEX > 0 {
            ViewController.INDEX = ViewController.INDEX - 1
            setLabelToIndex()
        }
    }

    // Go forward
    @IBAction func next(_ sender: Any?) {
        if ViewController.INDEX + 1 < content.count {
            ViewController.INDEX = ViewController.INDEX + 1
            setLabelToIndex()
        }
    }

    // Desired function to be called
    // when swiping back in navigation stack
    func onBack(index: Int) {
        ViewController.INDEX  -= 1;
        //setLabelToIndex()
    }


    override func didMove(toParentViewController parent: UIViewController?) {
        if parent == nil {
            self.onBack(index: ViewController.INDEX);
        }

    }

}

Answer 3

我可以告诉你，UINavigationController 支持的滑动是当用户开始将手指从屏幕左侧滑动到右侧时的滑动，只是为了从导航中弹出视图，你不能通过从右边缘向左滑动来将其推回在 iPhone 中，这是 UINavigationController 中的默认设置

我正在编写我的代码，因为我正在使用你需要相应地自定义它，我没有时间在办公室编辑，我会告诉你更多

#pragma mark for pageView
- (UIViewController *) viewControllerAtIndex:(NSUInteger)index
{
if (index > (self.imageArray.count-1))
    return nil;

UIViewController *viewController = nil;    ////
GalleryItems *item = self.imageArray[index];
NSString *cachedGalleryItemName = [item getCachedPhotoFileNameWithPath];
if ([[NSFileManager defaultManager] fileExistsAtPath:cachedGalleryItemName])
{
    ImageViewController *imageVC = [[ImageViewController alloc] initWithNibName:@"ImageViewController" bundle:nil];
    imageVC.galleryItem = item;
    imageVC.cachedGalleryItemName = cachedGalleryItemName;
    imageVC.index = index;
    viewController = imageVC;
}
else
{
    if (self.downloadViewController)
    {
        if (self.indexOfDownloadInProgress == index)
            viewController = self.downloadViewController;
        else
        {
            FileDownloader *fileDownloader = [DataDownloadManager existingFileDownloader:cachedGalleryItemName];
            if (! fileDownloader)
            {
                fileDownloader = [[FileDownloader alloc] init];
                [fileDownloader loadURL:item.photoURL forFilePath:cachedGalleryItemName withReceipt:nil];
                fileDownloader.delegate = nil;
                fileDownloader.notificationName = item.contentId;
                fileDownloader.queuePriority = NSOperationQueuePriorityNormal;
                [[DataDownloadManager sharedInstance].operationQueue addOperation:fileDownloader];
            }
        }
    }
    else
    {
        DownloadViewController *downloadVC = [[DownloadViewController alloc] initWithNibName:@"DownloadViewController" bundle:nil];
        downloadVC.delegate = self;
        downloadVC.downloadCompleteNotificationName = item.contentId;
        downloadVC.asset = item;
        downloadVC.backgroundImageFileName = nil;
        downloadVC.totalFileSize = nil;
        downloadVC.URLString = item.photoURL;
        downloadVC.cachedFileName = cachedGalleryItemName;
        self.indexOfDownloadInProgress = index;
        self.downloadViewController = downloadVC;
        viewController = downloadVC;
    }
}
return viewController;
}

现在使用这个函数来识别视图控制器

-(NSUInteger) indexOfViewController:(UIViewController *)viewController
{
NSUInteger index = nil;

if ([viewController isMemberOfClass:[ImageViewController class]])
{
    ImageViewController *currentViewController = (ImageViewController *)viewController;
    index = currentViewController.index;
}
else if ([viewController isMemberOfClass:[DownloadViewController class]])
    index = self.indexOfDownloadInProgress;

return index;
}

- (UIViewController *)viewController:(UIViewController *)viewController ForBeforeAfter:(NSInteger) beforeAfter
{
NSUInteger index = [self indexOfViewController:viewController];

if (index == NSNotFound)
    return nil;

index = index + beforeAfter;
if ([DataDownloadManager sharedInstance].internetNotAvailable)
{
    while (index < self.imageArray.count - 1)
    {
        GalleryItems *item = self.imageArray[index];
        if ([item isDownloaded])
            break;
        index = index + beforeAfter;
    }
}
return [self viewControllerAtIndex:index];
}

现在在页面视图控制器委托中执行此操作

-(UIViewController *)pageViewController:(UIPageViewController *)pageViewController viewControllerBeforeViewController:(UIViewController *)viewController
{
return [self viewController:viewController ForBeforeAfter:-1];
}

-(UIViewController *)pageViewController:(UIPageViewController *)pageViewController viewControllerAfterViewController:(UIViewController *)viewController
{
return [self viewController:viewController ForBeforeAfter:+1];
}

像这样初始化页面视图控制器

- (void)initPageViewController:(UIViewController *)initViewController
{
self.pageViewController = [[UIPageViewController alloc] initWithTransitionStyle:UIPageViewControllerTransitionStyleScroll navigationOrientation:UIPageViewControllerNavigationOrientationHorizontal options:nil];

[self.pageViewController setDataSource:self];

[self.pageViewController setViewControllers:@[initViewController] direction:UIPageViewControllerNavigationDirectionForward animated:YES completion:nil];

[self.pageViewController.view setFrame:self.view.frame];
[self addChildViewController:self.pageViewController];
[self.view addSubview:self.pageViewController.view];
[self.pageViewController didMoveToParentViewController:self];
[self.view sendSubviewToBack:self.pageViewController.view];
}

在类的viewDidLoad中（在我的例子中是DisplayImageViewController）你正在使用这个页面你可以添加这段代码来初始化

[self initPageViewController:[self viewControllerAtIndex:self.index]];

这个 DisplayImageViewController 类用于显示你刚刚删除 UIIMAGE 到你想要的东西的图像。

在导航中推送此视图控制器之前，请像这样设置属性

DisplayImageViewController *divc = initialize display view controller class; // here you just set the item in array in which you want to implement swipe
    divc.imageArray = self.imageArray;
    divc.galleryAsset = self.gallery;
    divc.index = indexPath.item;
    [self presentViewController:divc animated:YES completion:nil];