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。

这就是我写它的方式。 （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

有人可以帮助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Customize navigation bar for QLPreviewController 。 我删除它，它的工作完美。

我会给你两种摆脱不必要的sapce的方法：

1.删​​除代码：

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

2.如果您确实需要自定义导航栏的代码，请在PresentViewController之前添加以下代码PresentViewController ：

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

PresentViewController(previewController, true, completionHandler: null);

更新：

花了整个下午才发现解决方案并不完美。 首先，我想说的是， navigationBar你的viewController和navigationBar的QLPreviewController是两个不同的吧。

要设置导航AppDelegate颜色，只需在AppDelegate设置它，这将影响项目中的整个navigationBar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;
    }

要改变navigationbarColor的QLPreviewControl ，您可以使用代码test功能：

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功能会在演示完成之前调用，所以你会看到导航栏的默认颜色一段时间然后它会变成你想要的颜色。

如果你使用push动作而不是modal，你可以在WillShowViewController(UINavigationController navigationController, [Transient] UIViewController viewController, bool animated)里面调用test函数WillShowViewController(UINavigationController navigationController, [Transient] UIViewController viewController, bool animated) ：

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，您可以查看它： navigationBar-color-xamarin.forms