从 QLPreviewController 中删除不需要的顶部空间

Question

在我的应用程序中，我使用了 QLPreviewController 来显示一些 pdf 文件。一切正常，但 QLPreviewController 的内容顶部有一个不需要的空间，无法找到删除它的方法。

这是我写的。（请注意，我是 Xamarin.iOS 和 QLPreviewController 的新手）

public partial class ReportsViewController : UIViewController
{
    public override void ViewDidLoad()
    {
        base.ViewDidLoad();

        //Customize navigation bar for QLPreviewController
        if(UIDevice.CurrentDevice.CheckSystemVersion(11, 0)) // There is a bug with barTintColor on QLPreviewController for iOS 11 if you are showing it via presentViewController: animated:
        {
            var color = UIColor.FromRGB(red: 23, green: 61, blue: 86).CGColor;
            var rect = new CGRect(x: 0.0, y: 0.0, width: 1.0, height: 1.0);
            var alpha = color.Alpha;
            var opaque = alpha == 1;
            UIGraphics.BeginImageContextWithOptions(rect.Size, opaque, 0);
            var context = UIGraphics.GetCurrentContext();
            context.SetFillColor(color);
            context.FillRect(rect);
            var image = UIGraphics.GetImageFromCurrentImageContext();
            UIGraphics.EndImageContext();

            UINavigationBar.AppearanceWhenContainedIn(typeof(QLPreviewController)).SetBackgroundImage(image, UIBarMetrics.Default);

        }
        else // If iOS version is below 11.0
        {
            UINavigationBar.AppearanceWhenContainedIn(typeof(QLPreviewController)).BarTintColor = UIColor.FromRGBA(red: 255, green: 0, blue: 0, alpha: 1.0f);
        }

        UINavigationBar.AppearanceWhenContainedIn(typeof(QLPreviewController)).BarStyle = UIBarStyle.Black;
        UINavigationBar.AppearanceWhenContainedIn(typeof(QLPreviewController)).TintColor = UIColor.White;

        var reportSavedPath = "path to pdf file";
        var reportName = "Report name";
        var previewController = new QLPreviewController();
        var url = new NSUrl(reportSavedPath, true);
        var _dataSource = new PreviewControllerSource(this, url, reportName);
        previewController.DataSource = _dataSource;
        PresentViewController(previewController, true, completionHandler: null);
    }
}

public partial class ReportsViewController : UIViewController
{
    class PreviewControllerSource : QLPreviewControllerDataSource
    {
        ReportsViewController _parentClass = null;
        NSUrl _url = null;
        string _title = null;

        public PreviewControllerSource(ReportsViewController parentClass, NSUrl url, string title)
        {
            _parentClass = parentClass;
            _url = url;
            _title = title;
        }

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

        public override IQLPreviewItem GetPreviewItem(QLPreviewController controller, nint index)
        {
            return new PreviewItem { title = _title, url = _url };
        }
    }
    public class PreviewItem : QLPreviewItem
    {
        public string title { get; set; }
        public NSUrl url { get; set; }
        public override string ItemTitle { get { return title; } }
        public override NSUrl ItemUrl { get { return url; } }
    }
}

这是加载 pdf 时的样子

有人可以帮我删除这个不需要的空间吗？

Answer 1

不知道为什么必须在代码中使用Customize navigation bar for QLPreviewController。我删除了它，它工作得很好。

我会给你两种方法来摆脱不需要的空间：

1.删除代码：

//UINavigationBar.AppearanceWhenContainedIn(typeof(QLPreviewController)).SetBackgroundImage(image, UIBarMetrics.Default);

2.如果确实需要自定义导航栏的代码，在PresentViewController前加上这行代码：

//Add this line before PresentViewController
UINavigationBar.AppearanceWhenContainedIn(typeof(QLPreviewController)).SetBackgroundImage(null, UIBarMetrics.Default);

PresentViewController(previewController, true, completionHandler: null);

更新：

花了整个下午，才找到一个不太完美的解决方案。首先，我想说的是，你的viewController 的navigationBar 和QLPreviewController 的navigationBar 是两个不同的栏。

要设置导航栏的颜色，你可以简单地设置在AppDelegate，这会影响你项目中整个navigationBar的颜色。：

 public override bool FinishedLaunching(UIApplication application, NSDictionary launchOptions)
    {
        // Override point for customization after application launch.
        // If not required for your application you can safely delete this method

        UINavigationBar.Appearance.BarTintColor = UIColor.FromRGBA(red: 255, green: 0, blue: 0, alpha: 1.0f);
        UINavigationBar.Appearance.BarStyle = UIBarStyle.BlackOpaque;
        UINavigationBar.Appearance.TintColor = UIColor.White;


        return true;
    }

要更改QLPreviewControl的navigationbarColor，可以使用test函数中的代码：

public partial class ViewController : UIViewController
{

    QLPreviewController previewController;

    public ViewController(IntPtr handle) : base(handle)
    {
    }

    public override void ViewDidLoad()
    {
        base.ViewDidLoad();

        this.AutomaticallyAdjustsScrollViewInsets = false;
        this.ExtendedLayoutIncludesOpaqueBars = false;
        this.EdgesForExtendedLayout = UIRectEdge.None;

        string path = NSBundle.MainBundle.PathForResource("myPdf.pdf","");
        var reportName = "Report name";
        previewController = new QLPreviewController();
        var url = new NSUrl(path, true);
        var _dataSource = new PreviewControllerSource(this, url, reportName);
        previewController.DataSource = _dataSource;

        this.NavigationController.PresentViewController(previewController, true, test);

    }

    public void test() {

            var firstChild = previewController.ChildViewControllers[0];

            if (firstChild is UINavigationController)
            {
                var naviVc = firstChild as UINavigationController;
                naviVc.NavigationBar.BarTintColor = UIColor.Red ;
            }
        }
}

唯一不太完美的是test函数会一直调用到呈现完成，所以你会看到navigationBar的默认颜色一段时间，然后它会变成你想要的颜色。

如果您使用推送操作而不是模态，您可以在WillShowViewController(UINavigationController navigationController, [Transient] UIViewController viewController, bool animated) 中调用test 函数：

public class naviDeleagte : UINavigationControllerDelegate {

    public override void WillShowViewController(UINavigationController navigationController, [Transient] UIViewController viewController, bool animated)
    {
        //call test here if you use a push instead of modal
    }
}

我在这里上传了我的示例，您可以查看：navigationBar-color-xamarin.forms