Monotouch-QLPreviewController问题 [英] Monotouch - Issue with QLPreviewController

问题描述

我正在尝试使用QLPreviewController查看PDF文件并将其发送，但是预览PDF文档后操作按钮出现问题.

I am trying to use QLPreviewController to see a PDF file and send it, but I have an issue with the action button after previewing the PDF document.

当我按下操作按钮(在右上角)时，应用程序崩溃，我得到:未处理的托管异常:抛出了Objective-C异常.名称:NSInternalInconsistencyException原因:UIDocumentInteractionController:无效的方案(空).仅文件方案是支持.(MonoTouch.Foundation.MonoTouchException)"

When I press the action button (at the top right) app crashes and I get: "Unhandled managed exception: Objective-C exception thrown. Name: NSInternalInconsistencyException Reason: UIDocumentInteractionController: invalid scheme (null). Only the file scheme is supported. (MonoTouch.Foundation.MonoTouchException)"

我进行了一些研究，发现如果从Internet下载文件或文件类型不是"file://.........."，则可能会发生此问题. 我的NSUrl采用这种格式，所以我不知道为什么会出现此错误.

I did some research and it seams that this issue may occur if you download a file from the internet or if the file type is not "file:// .......... ". My NSUrl is on that format so I dont know why I have this error.

有人有什么主意吗?

谢谢

这是我调用控制器的代码:

Here is my code to call the Controller:

QLPreviewController previewController= new QLPreviewController();             

previewController.DataSource=new MyQLPreviewControllerDataSource();     

this.PresentViewController(previewController,true, null);

这是我的数据源代码:

public class MyQLPreviewControllerDataSource : QLPreviewControllerDataSource { public     override int PreviewItemCount (QLPreviewController controller) {

    return 1;
}

public override QLPreviewItem GetPreviewItem (QLPreviewController controller, int index)
{

    string fileName = @"example.pdf";
    var documents = Environment.GetFolderPath (Environment.SpecialFolder.MyDocuments);
    var library = Path.Combine (documents,fileName);
    NSUrl url = NSUrl.FromFilename (library);
    return new QlItem ("Title", url);
}
}

这是我的商品代码:

public class QlItem : QLPreviewItem { string _title; Uri _uri;

public QlItem (string title, Uri uri) 
{ 
    this._title = title; 
    this._uri = uri; 
} 

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

public override NSUrl ItemUrl { 
    get { return _uri; } 
} 

}

推荐答案

您的QlItem类将原始NSUrl投射到Uri中，然后再将其投射到NSUrl中，并且在此过程中会丢失某些内容.

Your QlItem class is casting the original NSUrl into a Uri before casting it back into a NSUrl and something is getting lost along the way.

它看起来应该更像:

    public class QlItem : QLPreviewItem 
    { 
        string title; 
        NSUrl uri; 

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

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

        public override NSUrl ItemUrl { 
            get { return uri; } 
        } 
    }                

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