Xamarin.Forms save file (pdf) in local storage and open with the default viewer

Question

Edited to fine the question

In Android, I need to download a pdf file to "Documents" folder and open it with the default program. I downloaded the document and stored it in a Byte array. Then I call this method:

    /// <summary>
    /// Save data bytes on "My documents" folder and open
    /// </summary>
    /// <param name="fileName">Filename, for example: "Test.pdf"</param>
    /// <param name="data">Array of bytes to save</param>
    /// <returns>True if success or false if error</returns>
    public bool SaveAndOpen(string fileName, byte[] data)
    {
        try
        {
            // Get my documents path
            string filePath = Path.Combine(Android.OS.Environment.ExternalStorageDirectory.AbsolutePath, Android.OS.Environment.DirectoryDownloads);
            // Combine with filename
            string fullName = Path.Combine(filePath, fileName);

            // If the file exist on device delete it
            if (File.Exists(fullName))
            {
                // Note: In the second run of this method, the file exists
                File.Delete(fullName);
            }

            // Write bytes on "My documents"
            File.WriteAllBytes(fullName, data);

            // Launch file as process
            Process.Start(fullName);

            return true;
        }
        catch (Exception ex)
        {
            Console.WriteLine("ERROR: " + ex.Message + ex.StackTrace);
            return false;
        }
    }

The problem is to open the pdf document with the default pdf reader.

The line "Process.Start(fullName);" throws an exception

System.ComponentModel.Win32Exception (0x80004005): Access denied

Thanks for your time!

Answer 1

I will extend @duefectu answer with class for reading file for more extensions Where MainActivity.MainActivityInstance is stored MainActivityContext

public void Open(string path)
{
    try
    {
        var url = new Java.IO.File(path);
        var uri = FileProvider.GetUriForFile(MainActivity.MainActivityInstance,
            MainActivity.MainActivityInstance.PackageName + ".fileprovider", url);

        var intent = new Intent(Intent.ActionView);
        if (url.ToString().Contains(".doc") || url.ToString().Contains(".docx"))
        {
            // Word document
            intent.SetDataAndType(uri, "application/msword");
        }
        else if (url.ToString().Contains(".pdf"))
        {
            // PDF file
            intent.SetDataAndType(uri, "application/pdf");
        }
        else if (url.ToString().Contains(".ppt") || url.ToString().Contains(".pptx"))
        {
            // Powerpoint file
            intent.SetDataAndType(uri, "application/vnd.ms-powerpoint");
        }
        else if (url.ToString().Contains(".xls") || url.ToString().Contains(".xlsx"))
        {
            // Excel file
            intent.SetDataAndType(uri, "application/vnd.ms-excel");
        }
        else if (url.ToString().Contains(".zip"))
        {
            // ZIP file
            intent.SetDataAndType(uri, "application/zip");
        }
        else if (url.ToString().Contains(".rar"))
        {
            // RAR file
            intent.SetDataAndType(uri, "application/x-rar-compressed");
        }
        else if (url.ToString().Contains(".rtf"))
        {
            // RTF file
            intent.SetDataAndType(uri, "application/rtf");
        }
        else if (url.ToString().Contains(".wav") || url.ToString().Contains(".mp3"))
        {
            // WAV audio file
            intent.SetDataAndType(uri, "audio/x-wav");
        }
        else if (url.ToString().Contains(".gif"))
        {
            // GIF file
            intent.SetDataAndType(uri, "image/gif");
        }
        else if (url.ToString().Contains(".jpg") || url.ToString().Contains(".jpeg") ||
                 url.ToString().Contains(".png"))
        {
            // JPG file
            intent.SetDataAndType(uri, "image/jpeg");
        }
        else if (url.ToString().Contains(".txt"))
        {
            // Text file
            intent.SetDataAndType(uri, "text/plain");
        }
        else if (url.ToString().Contains(".3gp") || url.ToString().Contains(".mpg") ||
                 url.ToString().Contains(".mpeg") || url.ToString().Contains(".mpe") ||
                 url.ToString().Contains(".mp4") || url.ToString().Contains(".avi"))
        {
            // Video files
            intent.SetDataAndType(uri, "video/*");
        }
        else
        {
            intent.SetDataAndType(uri, "*/*");
        }
        intent.SetFlags(ActivityFlags.ClearWhenTaskReset | ActivityFlags.NewTask | ActivityFlags.GrantReadUriPermission | ActivityFlags.NewTask);
        MainActivity.MainActivityInstance.StartActivity(intent);
    }
    catch (Exception exception)
    {
        
    }
}

Answer 2

I found a way to save and open the file:

    /// <summary>
    /// Save data bytes on "My documents" folder and open
    /// </summary>
    /// <param name="fileName">Filename, for example: "Test.pdf"</param>
    /// <param name="data">Array of bytes to save</param>
    /// <returns>True if success or false if error</returns>
    public bool SaveAndOpen(string fileName, byte[] data)
    {
        try
        {
            // Get my downloads path
            string filePath = Path.Combine(Android.OS.Environment.ExternalStorageDirectory.AbsolutePath, Android.OS.Environment.DirectoryDownloads);

            // Combine with filename
            string fullName = Path.Combine(filePath, fileName);

            // If the file exist on device delete it
            if (File.Exists(fullName))
            {
                // Note: In the second run of this method, the file exists
                File.Delete(fullName);
            }

            // Write bytes on "My documents"
            File.WriteAllBytes(fullName, data);

            // Get the uri for the saved file
            Android.Net.Uri file = Android.Support.V4.Content.FileProvider.GetUriForFile(
                this,
                this.PackageName + ".fileprovider",
                new Java.IO.File(fileName));
            Intent intent = new Intent(Intent.ActionView);
            intent.SetDataAndType(file, "application/pdf");
            intent.SetFlags(ActivityFlags.ClearWhenTaskReset | ActivityFlags.NewTask | ActivityFlags.GrantReadUriPermission | ActivityFlags.NewTask);
            this.ApplicationContext.StartActivity(intent);

            return true;
        }
        catch (Exception ex)
        {
            Console.WriteLine("ERROR: " + ex.Message + ex.StackTrace);
            return false;
        }
    }

It's needed to request the permissions at runtime. I used Plugin.Permisions available on Nuget:

    Plugin.Permissions.PermissionsImplementation.Current.RequestPermissionsAsync(
         new Plugin.Permissions.Abstractions.Permission[]
         {
             Plugin.Permissions.Abstractions.Permission.Storage,
             Plugin.Permissions.Abstractions.Permission.MediaLibrary
         });

Also add a provider in the AndroidManifest.xml file:

<application android:label="My app" android:icon="@mipmap/icon">
    <provider android:name="android.support.v4.content.FileProvider" android:authorities="${applicationId}.fileprovider" android:exported="false" android:grantUriPermissions="true">
        <meta-data android:name="android.support.FILE_PROVIDER_PATHS" android:resource="@xml/file_paths"></meta-data>
    </provider>
</application>

In the same AndroidManifest add permisions for:

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

And add an external path in Resources/xml/file_paths.xml

<external-path name="external_files" path="."/>

Don't know if I have not needed permissions, but with this way works.