如何从Xamarin.Android中的Assets文件夹中打开pdf

Question

I want to Open a PDF in any PDFviewer and my pdf file is placed in assets folder.

I tried doing following but File Provider also plays a part since targetversion>24. I have also implemented a FileProvider in Manifest file and a filepath file in xml folder under resources. Please help.

 string fileName = "myProfile.pdf";

 var localFolder = Android.OS.Environment.ExternalStorageDirectory.AbsolutePath;
 var MyFilePath = System.IO.Path.Combine(localFolder, fileName);

 using (var streamReader = new StreamReader(_activity.Assets.Open(fileName)))
 {
      using (var memstream = new MemoryStream())
      {
           streamReader.BaseStream.CopyTo(memstream);
           var bytes = memstream.ToArray();
           //write to local storage
           System.IO.File.WriteAllBytes(MyFilePath, bytes);

           MyFilePath = $"file://{localFolder}/{fileName}";
      }
 }

 var fileUri = Android.Net.Uri.Parse(MyFilePath);
 Intent intent = new Intent(Intent.ActionView);
 intent.SetDataAndType(fileUri, "application/pdf");
 intent.SetFlags(ActivityFlags.ClearTop);
 intent.SetFlags(ActivityFlags.NewTask);
 try
 {
      _activity.StartActivity(intent);
 }
 catch (ActivityNotFoundException ex)
 {
      Toast.MakeText(_activity, "NO Pdf Viewer", ToastLength.Short).Show();
 }

Answer 1

This is how I use intent chooser to do the above:

Get the stream from the assets folder using below:

      public Stream GetFromAssets(Context context, string assetName)
    {
        AssetManager assetManager = context.Assets;
        Stream inputStream;
        try
        {
            using (inputStream = assetManager.Open(assetName))
            {
                return inputStream;
            }

        }
        catch (Exception e)
        {
            return null;
        }
    }

Add the following helper method to for byte[] conversion:

    public byte[] ReadFully(Stream input)
    {
        using (MemoryStream ms = new MemoryStream())
        {
            input.CopyTo(ms);
            return ms.ToArray();
        }

Then update the Open pdf method as follows and it should work:

    private void OpenPDF(Stream inputStream)
    {
        var bytearray = ReadFully(inputStream);
        Java.IO.File file = (Java.IO.File)Java.IO.File.FromArray(bytearray);
        var target = new Intent(Intent.ActionView);
        target.SetDataAndType(Android.Net.Uri.FromFile(file), "application/pdf");
        target.SetFlags(ActivityFlags.NoHistory);

        Intent intent = Intent.CreateChooser(target, "Open File");
        try
        {
            this.StartActivity(intent);
        }
        catch (ActivityNotFoundException ex)
        {
            // Instruct the user to install a PDF reader here, or something
        }
    }

Where I pass the string path of my pdf file to come up with a Java.IO.File

Basically, add the following using statements:

using Java.IO;
using Android.Content;
using Android.Net;

Revert in case of queries

Goodluck!