尝试呈现其视图不在窗口层次结构中的 Xamarin_Forms_Platform_iOS_NavigationRenderer

Question

大家好，我遇到了这个问题： 尝试在 谁的视图不在窗口层次结构中！ 有人知道如何创建一个 UINavigationController 来打开 iOS 中的 PDF 文件 我为 Android 和 iOS 创建 Dependecy 服务，但仅 在 Android 和 iOS 中工作，PDF 出现，而​​没有出现 我尝试搜索一种使用 UIViewController 实现但不起作用的方法 这是课

public class SaveFile : ISaveFile
{

    public async Task<string> SaveFiles(string filename, byte[] bytes)
    {

        try
        {
            var documentsPath = System.Environment.GetFolderPath(System.Environment.SpecialFolder.MyDocuments);
            var filePath = Path.Combine(documentsPath, filename);

            File.WriteAllBytes(filePath, bytes);
            OpenPDF(filePath);
            //OpenFile(filePath);
            return filePath;
        }
        catch(Exception ex)
        {
            Debug.WriteLine("Error" + ex.Message + ex.StackTrace);
            return "";
        }
    }

    public  void OpenPDF(string filePath)
    {
          FileInfo fi = new FileInfo(filePath);

        QLPreviewController previewController = new QLPreviewController();


        previewController.DataSource = new PDFPreviewControllerDataSource(fi.FullName, fi.Name);

        //UIView uIView = previewController.View;
             UINavigationController controller = FindNavigationController();
        controller.ModalPresentationStyle = UIModalPresentationStyle.FullScreen;
        if (controller != null)

                  controller.PresentViewController(previewController, true,null);


    }

    /*
    public void OpenFile(string filePath)
    {
        var viewer = UIDocumentInteractionController.FromUrl(NSUrl.FromFilename(filePath));
        var controller = GetVisibleViewController();
        viewer.PresentOpenInMenu(controller.View.Frame, controller.View, true);
    }




    //*/

    private UINavigationController FindNavigationController()
    {
        foreach (var window in UIApplication.SharedApplication.Windows)
        {
            if (window.RootViewController.NavigationController != null)
                return window.RootViewController.NavigationController;
            else
            {
                UINavigationController val = CheckSubs(window.RootViewController.ChildViewControllers);
                if (val != null)
                    return val;
            }
        }

        return null;
    }

    private UINavigationController CheckSubs(UIViewController[] controllers)
    {
        foreach (var controller in controllers)
        {
            if (controller.NavigationController != null)
                return controller.NavigationController;
            else
            {
                UINavigationController val = CheckSubs(controller.ChildViewControllers);
                if (val != null)
                    return val;
            }
        }
        return null;
    }



    public class PDFItem : QLPreviewItem
    {
        string title;
        string uri;

        public PDFItem(string title, string uri)
        {
            this.title = title;
            this.uri = uri;
        }

        public override string ItemTitle
        {
            get { return title; }
        }

        public override NSUrl ItemUrl
        {
            get { return NSUrl.FromFilename(uri); }
        }


    }

    public class PDFPreviewControllerDataSource : QLPreviewControllerDataSource
    {
        string url = "";
        string filename = "";

        public PDFPreviewControllerDataSource(string url, string filename)
        {
            this.url = url;
            this.filename = filename;
        }

        public override IQLPreviewItem GetPreviewItem(QLPreviewController controller, nint index)
        {
            return (IQLPreviewItem)new PDFItem(filename, url);
        }

        public override nint PreviewItemCount(QLPreviewController controller)
        {
            return 1;
        }


    }
}

Answer 1

您可以查看this answer 以了解您收到的错误消息。

解决方案：

删除 find FindNavigationController 方法并使用 UIApplication.SharedApplication.KeyWindow.RootViewController.PresentViewController 呈现 QLPreviewController ：

   public void OpenPDF(string filePath)
    {
        FileInfo fi = new FileInfo(filePath);

        QLPreviewController previewController = new QLPreviewController();


        previewController.DataSource = new PDFPreviewControllerDataSource(fi.FullName, fi.Name);

        UIApplication.SharedApplication.KeyWindow.RootViewController.PresentViewController(previewController, true, null);


        //UIView uIView = previewController.View;
        //UINavigationController controller = FindNavigationController();
        //controller.ModalPresentationStyle = UIModalPresentationStyle.FullScreen;
        //if (controller != null)

        //    controller.PresentViewController(previewController, true, null);


    }

顺便说一句，你也可以使用 webview 加载 pdf 文件。