Share file .txt Android

Question

I'm trying to share a .txt file to another app (gmail for example) but I have some problems. I decided to use the file provider. When I select gmail among the apps to share the file with, the app returns me the "Couldn't attach file" toast.

I write the file txt in internal memory with this method:

public void esportaTxt(Graph graph, int id){
        final String FILE_NAME = id + "_TXT" + ".txt";
        List<Zona> zone = new ArrayList<>();
        Iterator<Zona> iterator = graph.vertexSet().iterator();

        zone = fromIteratorToArrayZone(iterator);

        File fileOutputFolder = new File(context.getFilesDir(), "fileOutput"); //cartella in cui salvare i file da condividere

        FileOutputStream fileOutputStream = null;
        try {
            fileOutputFolder.mkdirs(); //crea la cartella se non esiste
            File file = new File(fileOutputFolder, FILE_NAME); //il file da salvare

            fileOutputStream = new FileOutputStream(file);

            for(int i = 0; i < zone.size(); i++){
                fileOutputStream.write((i + 1 + ") " + zone.get(i).getNome() + "\n").getBytes());

                Iterator<Oggetto> iteratoreOggetti = zone.get(i).getListaOggetti().iterator();
                while (iteratoreOggetti.hasNext()){
                    fileOutputStream.write(("   - " + iteratoreOggetti.next().getNome() + "\n").getBytes());
                }
            }

            contentUri = FileProvider.getUriForFile(context, "com.example.eculturetool.fileprovider", file);

        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if(fileOutputStream != null){
                try {
                    fileOutputStream.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }

I share the file txt with the following method:

public void shareFileTxt(int id){
        String fileName = id + "_TXT.txt";
        String stringFile = context.getFilesDir() +  "/fileOutput" +  File.separator + fileName;

        File file = new File(stringFile);
        contentUri = FileProvider.getUriForFile(context, "com.example.eculturetool.fileprovider", file);

        if(!file.exists()){
            Toast.makeText(context, "Il file non esiste!", Toast.LENGTH_LONG).show();
            return;
        }


        Intent intentShare = new Intent(Intent.ACTION_SEND);
        intentShare.setType("text/*");
        intentShare.putExtra(Intent.EXTRA_SUBJECT, "Subject Here"); //per condividere con email app
        intentShare.putExtra(Intent.EXTRA_STREAM, contentUri);
        intentShare.addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION);
        context.startActivity(Intent.createChooser(intentShare, "Condividi file"));
    }

The permissions that I require in the Activity:

ActivityCompat.requestPermissions(this, new String[]{READ_EXTERNAL_STORAGE, WRITE_EXTERNAL_STORAGE}, PERMISSION_GRANTED);
        StrictMode.VmPolicy.Builder builder = new StrictMode.VmPolicy.Builder();
        StrictMode.setVmPolicy(builder.build());

Provider in android manifest:

<provider
            android:name="androidx.core.content.FileProvider"
            android:authorities="com.example.eculturetool.fileprovider"
            android:exported="false"
            android:grantUriPermissions="true">
            <meta-data
                android:name="android.support.FILE_PROVIDER_PATHS"
                android:resource="@xml/file_paths" />
        </provider>

The screen of Gmail

Answer 1

you must grant uri permission before starting intentShare , like this code:

context.grantUriPermission(
                "your.package.name",
                contentUri,
                Intent.FLAG_GRANT_WRITE_URI_PERMISSION or Intent.FLAG_GRANT_READ_URI_PERMISSION
            )