Xamarin.Forms Android 不包含 Content 的定义

Question

I am trying to create/Open/Write a .txt file in the External Storage, but I can not set the path with " Android.Content.Context.GetExternalFilesDir ".

Here is my exact code:

string sourceFile = Path.Combine(Android.Content.Context.GetExternalFilesDir(null).AbsolutePath, "myFile.txt");
File.Create(sourceFile);

The error message is:

Android doesn't contain a definition for Content

What should I do?
I don't know how to modify the assembly

Answer 1

Of course, if you create a Xamarin.Android project, you can use the android api easily in it.

In addition, you can also call the platform method with the dependency service. You can check the following link which shows how to use it to operate the android folder.

Link: Xamarin forms: How to create folder and a file in device external storage?

And then you need to add the write and read the external storage permission in the AndroidManifest.xml:

<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

And grant the app the two permission with the permission request. You can check the following case.

Case: Can't write to Android External storage even with permissions set

In addition, you need to put the SaveFile(string fileName) method into the AccessFileImplement class.

Answer 2

I am still on the same point, here is what I did: in the Android Project , I created a class "Storage" ( Storage.cs ) with this function:

 public void SaveFile(string fileName)
    {
        string path = Android.OS.Environment.ExternalStorageDirectory.AbsolutePath;
        string filePath = System.IO.Path.Combine(path, fileName);
        if (!System.IO.File.Exists(filePath))
        {
            using (System.IO.StreamWriter writer = new System.IO.StreamWriter(filePath, true))
            {
                writer.WriteLine(DateTime.Now.ToString() + ": " + "Example .txt created using Xamarin.");
            }
        }
        else
        {
            System.IO.File.Delete(filePath);
            using (System.IO.StreamWriter writer = new System.IO.StreamWriter(filePath, true))
            {
                writer.WriteLine(DateTime.Now.ToString() + ": " + "Example .txt created using Xamarin.");
            }
        }
    }

Then in the Forms Project , in MainPage.xaml.cs I added an interface with this code:

public interface IAccessFile
    {
        void SaveFile(string fileName);
    }

And then in the same item ( MainPage.xaml.cs ) in the main code, I added:

DependencyService.Get<IAccessFile>().SaveFile("workingHours.txt");

Also in AndroidManifest.xml , I added the permission:

<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

The only code I did not add in the Android Project in my class Storage (before the function) is:

[assembly: Xamarin.Forms.Dependency(typeof(AccessFileImplement))]
namespace XamarinFirebase.Droid
{
    public class AccessFileImplement : IAccessFile

Because it doesn't work even with the using