Adroid write to files.

[sstahurski]

Having problems writing then reading files Xamarian Android application.

Its the same issue posted to here....
http://stackoverflow.com/questions/21999804/cross-platform-solution-to-isolated-storage-in-pcl/37439443#37439443

I have my permissions set correctly to read/write external storage in my android manifest file.

Reading the data I get this exception
ex {PCLStorage.Exceptions.FileNotFoundException: File does not exist: /data/data/com.bconnect.expo/files…} PCLStorage.Exceptions.FileNotFoundException

This is after the write appears to be successful.

Shouldn't the file name be '/Android/data/com.bconnect.expo/files....' ?

Here is my code, as you can see I'm not doing really anything more than what the examples give

    private async void writeDeviceData ()
    {
        IFolder rootFolder = FileSystem.Current.LocalStorage;

        //load everything into a dictionary
        Dictionary<string,string> expoContents = new Dictionary<string, string>();

                    //omitted.... for size

        //create file
        IFile outFile = await rootFolder.CreateFileAsync("ExpoFile.txt", CreationCollisionOption.ReplaceExisting);

        //write to file
        var strContents = JsonConvert.SerializeObject(expoContents);

        try
        {
            await outFile.WriteAllTextAsync( strContents );

        }
        catch(Exception ex) 
        {

        }

    }

    private async void readDeviceData ()
    {

        IFolder rootFolder = FileSystem.Current.LocalStorage;

        try{
            IFile inFile = await rootFolder.GetFileAsync("Expofile.txt");
            string strContents = inFile.ReadAllTextAsync ().Result;
                              //...omitted for size
            }
        }
        catch ( Exception ex)
        {
            //go out to web service
            reloadSiteData ();
        }

    }

[Blackhex]

I can confirm this issue on MemoPad 7 with Android 4.4.2.

[Emasoft]

I have the same problem.
On iOS it works fine. But on Android I get the same bug.
On Android I first write the file correctly (I checked with the AndroidDeviceMonitor file browser). So I'm sure that the file is there and the path is correct. Then I load it from the cache, and then I get the file not found error. This is the exception:

GetCachedBadge: PCLStorage.Exceptions.FileNotFoundException: File does not exist: /storage/emulated/0/toolbar/y62d2ke8.ink/36D99203@3x.png
  at PCLStorage.FileSystemFolder+<GetFileAsync>d__6.MoveNext () [0x000bc] in <filename unknown>:0 
--- End of stack trace from previous location where exception was thrown ---
  at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw () [0x0000c] in /Users/builder/data/lanes/3540/1cf254db/source/mono/external/referencesource/mscorlib/system/runtime/exceptionservices/exceptionservicescommon.cs:143 
  at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Threading.Tasks.Task task) [0x00047] in /Users/builder/data/lanes/3540/1cf254db/source/mono/external/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:187 
  at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Threading.Tasks.Task task) [0x0002e] in /Users/builder/data/lanes/3540/1cf254db/source/mono/external/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:156 
  at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd (System.Threading.Tasks.Task task) [0x0000b] in /Users/builder/data/lanes/3540/1cf254db/source/mono/external/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:128 
  at System.Runtime.CompilerServices.TaskAwaiter`1[TResult].GetResult () [0x00000] in /Users/builder/data/lanes/3540/1cf254db/source/mono/external/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:357 
  at ToolbarBadgeSample.Controls.ToolbarItemEx+<GetCachedBadge>c__async2.MoveNext () [0x000bb] in /Users/Admin/Projects/xamarin-samples-12545da4b6e715faedbb247c8a9ffa04f6d7a7e9/ToolbarBadgeSample/ToolbarBadgeSample/ToolbarBadgeSample/Controls/ToolbarItemEx.cs:348 
Could not load image named: {0}: /storage/emulated/0/toolbar/y62d2ke8.ink/36D99203@3x.png

I checked my code, and it is fine. It asks for the correct path and filename.
But the PCLStorage library is not able to found it for some reasons.

[zippo227]

@Emasoft I'm having a similar issue on uwp. I'm thinking it may have to do with file permissions.

[zippo227]

@Emasoft I wrote up the bug for UWP, which I supppose is different from your Android bug. issue 58

I was having a bug similar to yours on Android the other day. I think part of it was that I was writing the files in parallell. Once I blocked the write function with a SemaphoreSlim, I was able to read the files after writing them.

private SemaphoreSlim writeLock = new SemaphoreSlim(1, 1);
private async Task<string> CacheFileHelper(string filename, MemoryStream stream)
{
	await writeLock.WaitAsync();

	try
	{
		IFile file;
		file = await FileSystem.Current.LocalStorage.CreateFileAsync(filename, CreationCollisionOption.ReplaceExisting);
		using (var fileStream = await file.OpenAsync(PCLStorage.FileAccess.ReadAndWrite))
		{
			byte[] imgBytes = stream.ToArray();
			await fileStream.WriteAsync(imgBytes, 0, imgBytes.Length);
		}

		string path = file.Path;
		return path;
	}
	catch(Exception ex)
	{
		Console.WriteLine(ex.Message);
	}
	finally
	{
		writeLock.Release();
	}

	return string.Empty;
}