如何將XML文件加載到Xamarin Android

Question

我將Xml文件保存在Assets文件夾中，並在嘗試將更改保存到xml文件時將Build Action設置為Android Assets，它會給出異常System.UnauthorizedAccessException：拒絕訪問路徑“ /Q317664.xml”。我不確定為什么發生這種異常，請幫幫我

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

應用程序捆綁包中的Assets目錄是只讀的，您無法寫入打開的Q317664.xml xml文檔。 這是System.UnauthorizedAccessException的原因。

如果要修改資產目錄中捆綁的內容，請將其提取到可寫位置，然后對該副本進行操作：

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");

看到：

• 資產文件夾是只讀的嗎？
• 如何將文件寫入Android中的Assets文件夾或Raw文件夾？

Answer 2

您需要將XML文件添加到Xamarin Android項目中的Assets文件夾中

然后您可以像這樣將Xml加載到變量中

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