Mono for Android External (SD card) File IO - file-io

Question

I'm trying to create my first Mono for Android application, and have had permission errors trying to read or write from/to the sdcard. So I've switched to the SanityTests, xamarin-monodroid-samples-d76baf3.
Example_WorkingWithAudio RecordAudio.cs works successfully on internal storage. It also has the WRITE_EXTERNAL_STORAGE permission applied in the manifest; so I then uncommented the lines:
Java.IO.File sdDir = Android.OS.Environment.GetExternalStoragePublicDirectory(Android.OS.Environment.DirectoryMusic);
filePath = sdDir + "/" + "testAudio.mp3";
So that the code now reads:
Java.IO.File sdDir = Android.OS.Environment.GetExternalStoragePublicDirectory(Android.OS.Environment.DirectoryMusic);
filePath = sdDir + "/" + "testAudio.mp3";
Java.IO.File myFile = new Java.IO.File(filePath);
myFile.CreateNewFile();
I am executing this on a Sony Ericsson Xperia Mini Pro which runs Android 2.3.4.
When execution gets to the CreateNewFile() line, filePath has the value: "/mnt/sdcard/Music/testAudio.mp3".
This error is then thrown:
Java.IO.IOException: Exception of type 'Java.IO.IOException' was thrown.
at Android.Runtime.JNIEnv.CallBooleanMethod (IntPtr jobject, IntPtr jmethod) [0x00023] in /Users/builder/data/lanes/monodroid-mac-monodroid-4.2.6-
branch/632e6ddf/source/monodroid/src/Mono.Android/src/Runtime/JNIEnv.g.cs:156
at Java.IO.File.CreateNewFile () [0x0003e] in /Users/builder/data/lanes/monodroid-mac-monodroid-4.2.6-
branch/632e6ddf/source/monodroid/src/Mono.Android/platforms/android-8/src/generated/Java.IO.File.cs:771
at Example_WorkingWithAudio.RecordAudio.StartRecorder () [0x00044] in c:\Users\Matt\Downloads\xamarin-monodroid-samples-d76baf3\xamarin-monodroid-samples-
d76baf3\Example_WorkingWithAudio\Example_WorkingWithAudio\RecordAudio.cs:35
--- End of managed exception stack trace ---
java.io.IOException: Permission denied
at java.io.File.createNewFileImpl(Native Method)
at java.io.File.createNewFile(File.java:1257)
at mono.android.view.View_OnClickListenerImplementor.n_onClick(Native Method)
at mono.android.view.View_OnClickListenerImplementor.onClick(View_OnClickListenerImplementor.java:29)
at android.view.View.performClick(View.java:2552)
at android.view.View$PerformClick.run(View.java:9229)
at android.os.Handler.handleCallback(Handler.java:587)
at android.os.Handler.dispatchMessage(Handler.java:92)
at android.os.Looper.loop(Looper.java:130)
at android.app.ActivityThread.main(ActivityThread.java:3701)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:507)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:866)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:624)
at dalvik.system.NativeStart.main(Native Method)
What's the prob?
FYI, I also tried using the .Net classes:
FileStream fileStream = File.Create(filePath);
(where filePath is still "/mnt/sdcard/Music/testAudio.mp3")
But that line gives the exception:
System.IO.DirectoryNotFoundException: Could not find a part of the path "/mnt/sdcard/Music/testAudio.mp3".
at System.IO.FileStream..ctor (System.String path, FileMode mode, FileAccess access, FileShare share, Int32 bufferSize, Boolean anonymous, FileOptions options) [0x00000] in <filename unknown>:0
at System.IO.FileStream..ctor (System.String path, FileMode mode, FileAccess access, FileShare share, Int32 bufferSize) [0x00000] in <filename unknown>:0
at System.IO.File.Create (System.String path, Int32 bufferSize) [0x00000] in <filename unknown>:0
at System.IO.File.Create (System.String path) [0x00000] in <filename unknown>:0
at Example_WorkingWithAudio.RecordAudio.StartRecorder () [0x0001d] in c:\Users\Matt\Downloads\xamarin-monodroid-samples-d76baf3\xamarin-monodroid-samples-d76baf3\Example_WorkingWithAudio\Example_WorkingWithAudio\RecordAudio.cs:33

Answer 1

This is how I have done this in Mono for Android.
var path = Android.OS.Environment.ExternalStorageDirectory.AbsolutePath;
path = Path.Combine(path, "testaudio.mp3");

Answer 2

I was running into the same exception and finally got it resolved by doing the following:
Create an sdcard file for the emulator. I wrote a post with a simple tutorial describing how to do this.
Using the code below (C#), I was able to write a file to the sdcard:
string pathToFile = Path.Combine(Android.OS.Environment.ExternalStorageDirectory.AbsolutePath, _fileName);
using(var fileStream = new FileStream(pathToFile, FileMode.Append, FileAccess.Write, FileShare.None))
{
fileStream.Write(Encoding.ASCII.GetBytes(message), 0, Encoding.ASCII.GetByteCount(message));
}

Answer 3

if you are trying to downloading or get images from a server with xamarin forms you can use this:
File.WriteAllBytes("myimage.png",
new WebClient().DownloadData(http://www.dotnetperls.com/net.png));

Answer 4

Try this path:
String filePath = Environment.getExternalStorageDirectory() + "/testAudio.mp3";
File mFile = new File(filePath);