我正在使用HtmlAgilityPack以便从翻译工具的Google Translate中抓取信息。我已经下载了HtmlAgilityPack dll,并在程序中成功引用了它。我在Unity中使用Assembly。以下是这两个程序的代码:

using UnityEngine;
using System.Collections;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Net;
using HtmlAgilityPack;

public class GUIScript : MonoBehaviour {
    private string textField = "";
    private string input;
    public Texture2D icon;
    Dictionary search;
    Encoding code;
    // Use this for initialization
    void Start () {
        search = new Dictionary();
        input = " ";
        code = Encoding.UTF8;
        //This is what is run to translate
        print (search.Translate("Hola","es|en",code));
    }

    // Update is called once per frame
    void Update () {

    }
    void OnGUI(){
        textField = GUI.TextField(new Rect(0, Screen.height -50, Screen.width-80, 40), textField);
        if(GUI.Button(new Rect(Screen.width-80, Screen.height -50, 80,40), icon)){
            input = textField;
            textField = "";

        }
        //GUI.Label(new Rect(0,Screen.height -70, Screen.width-80,20), search.Translate("Hola","es|en",code));
        //print (search.Translate("Hola","es|en",code));
    }
}


这是引用我的Dictionary类的代码,如下所示:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using UnityEngine;
using System.Collections;
using System.Net;
using HtmlAgilityPack;


public class Dictionary{
    string[] formatParams;
    HtmlDocument doc;
    public Dictionary(){
        formatParams = new string[2];
        doc = new HtmlDocument();
    }
    public string Translate(String input, String languagePair, Encoding encoding)
     {
        formatParams[0]= input;
        formatParams[1]= languagePair;
        string url = String.Format("http://www.google.com/translate_t?hl=en&ie=UTF8&text={0}&langpair={1}", formatParams);

        string result = String.Empty;

        using (WebClient webClient = new WebClient())
        {
            webClient.Encoding = encoding;
            result = webClient.DownloadString(url);
        }
        doc.LoadHtml(result);
        return doc.DocumentNode.SelectSingleNode("//span[@title=input]").InnerText;
    }
    // Use this for initialization
    void Start () {

    }
}


运行此命令时,出现错误:

NullReferenceException: Object reference not set to an instance of an object
Dictionary.Translate (System.String input, System.String languagePair,System.Text.Encoding encoding) (at Assets/Dictionary.cs:32)
GUIScript.Start () (at Assets/GUIScript.cs:22)


我曾尝试过更改代码,查找解决方案,HtmlDocument的API以及如何修复NullReferenceExceptions,但是由于某些原因,我无法弄清楚为什么得到NullReferenceException。这个问题已经使我退缩了一个星期或两个星期,我需要继续进行我的项目。任何帮助将不胜感激!

最佳答案

如果我计数正确,则是第32行:

return doc.DocumentNode.SelectSingleNode("//span[@title=input]").InnerText


这意味着doc.DocumentNode为null或DocumentNode.SelectSingleNode("//span[@title=input]")返回null。

如果是前者,请检查是否收到了实际的文件。您的网址可能未正确编码。另见why HTML Agility Pack HtmlDocument.DocumentNode is null?

如果是后者,那么XPath可能会发生一些奇怪的事情。我不知道这有多重要,因为DocumentNode应该是文档的基础,在http://htmlagilitypack.codeplex.com/discussions/249129上的讨论可能适用。因此,“ //”是从文档的根开始搜索的,您可能不得不尝试doc.DocumentNode.SelectSingleNode(".//span[@title=input]")(在字符串的开头添加.)。

调试方法并准确查看这些调用的值即可完成工作。

关于c# - C#中带有HtmlDocument引用的NullReferenceException,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/13031757/

10-10 12:42