如何将xml文件加载到xamarin android

Question

我将 Xml 文件保存在 Assets 文件夹中并将 Build Action 设置为 Android Assets，当我尝试将更改保存到 xml 文件时，它会给出异常 System.UnauthorizedAccessException: Access to the path "/Q317664.xml" is denied.i不知道为什么会发生这个异常，请帮助我

using System;
using Android.App;
using Android.Content;
using Android.Runtime;
using Android.Views;
using Android.Widget;
using Android.OS;
using System.IO;
using System.Reflection;
using Android.Content.Res;
using System.Xml;
using System.Xml.Linq;
using System.Xml.XPath;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace App17 
{
[Activity(Label = "App17", MainLauncher = true, Icon = "@drawable/icon")]
public class MainActivity : Activity
{
    int count = 1;

    protected override void OnCreate(Bundle bundle)
    {
        base.OnCreate(bundle);

        // Set our view from the "main" layout resource
        SetContentView(Resource.Layout.Main);

        // Get our button from the layout resource,
        // and attach an event to it
        var xml = XDocument.Load(Assets.Open("Q317664.xml"));
        var node = xml.Descendants("Book").FirstOrDefault(cd => cd.Attribute("Id").Value == "1");
        node.SetAttributeValue("ISBN", "new");
        xml.Save("Q317664.xml");
     //   Button button = FindViewById<Button>(Resource.Id.MyButton);

       // button.Click += delegate { button.Text = string.Format("{0} clicks!", count++); };
    }
}
}

Answer 1

应用程序包中的Assets 目录是只读的，您无法写入您打开的Q317664.xml xml 文档。这就是System.UnauthorizedAccessException 的原因。

如果您想修改捆绑在资产目录中的内容，请将其解压缩到可写位置，然后对该副本进行操作：

string fileName = "Q317664.xml";
string filePath = Path.Combine (Android.OS.Environment.ExternalStorageDirectory.ToString (), fileName);
// Check if your xml file has already been extracted.
if (!File.Exists(filePath))
{
    using (BinaryReader br = new BinaryReader(Assets.Open(fileName)))
    {
        using (BinaryWriter bw = new BinaryWriter(new FileStream(dbPath, FileMode.Create)))
        {
            byte[] buffer = new byte[2048];
            int len = 0;
            while ((len = br.Read(buffer, 0, buffer.Length)) > 0)
            {
                bw.Write (buffer, 0, len);
            }
        }
    }
}

// Operate on the external file
var xml = XDocument.Load(filePath);
var node = xml.Descendants("Book").FirstOrDefault(cd => cd.Attribute("Id").Value == "1");
node.SetAttributeValue("ISBN", "new");
xml.Save("Q317664.xml");

见：

• Is Asset folder read-only?
• How to write files to assets folder or raw folder in android?

Answer 2

您需要将 XML 文件添加到 Xamarin Android 项目的 Assets 文件夹中

然后你可以像这样将 Xml 加载到变量中

var xml = XDocument.Load(Assets.Open("data.xml"));