Create CSV file with the right permissions

Question

I am building an Android app where I want to export some values to a CSV. I have to problem: either I get an error saying that the permission is denied or I get no errors but no CSV is created.

    FileWriter writer;
    File root = Environment.getExternalStorageDirectory();
    File csvFile = new File(root, "xxx.csv");
    writer = new FileWriter(csvFile);

    String headers = String.format("%s,%s\n", "Timestamp",
            "Value");
    writer.write(headers);
    writer.flush();
    writer.close();

But i get nothing...

This question already have a question. check [link](https://stackoverflow.com/questions/11341931/how-to-create-a-csv-on-android) — Ahmed Nezhi, Nov 16 '20 at 16:14
i have tried this before and it didn't work. I have tried many tutorials but I can never find the file in the phone — Antoine de Pommereau, Nov 16 '20 at 16:58

Vivek Vashistha · Answer 1 · 2023-01-14T12:11:48.343

From Android 10 and beyond, Android enforces Storage Scope Model. You can either write your CSV file in App-Specific Location which is private to your App and doesn't require any user permission, but no one can access this location. Here is the code snippet to write the file into the App-Specific directory:

 public void writeIntoFile(Context context, String fileName, String content) {
//        File appSpecificExternalStorageDirectory = context.getExternalFilesDir(Environment.DIRECTORY_DOCUMENTS);
        File appSpecificInternalStorageDirectory = context.getFilesDir();
        File file = new File(appSpecificInternalStorageDirectory, fileName);
        file.createNewFile();
        FileOutputStream fos = new FileOutputStream(file, false);
        fos.write(content.getBytes());
        fos.close();
    }

If you want to share this file with the User, then you should write this file in Shared Storage. To write a file in Shared Storage, this has to be done in 3 steps:-

Step 1: Launch System Picker to choose the destination by the user. This will return Uri of the destination directory.

private ActivityResultLauncher<Intent> launcher; // Initialise this object in Activity.onCreate()
private Uri baseDocumentTreeUri;
public void launchBaseDirectoryPicker() {
        Intent intent = new Intent(Intent.ACTION_OPEN_DOCUMENT_TREE);
        launcher.launch(intent);
 }

Step 2: Launch System Picker to choose the destination by the user. This will return the Uri of the destination directory. Also, you can optionally persist the permissions and Uri for future use.

@Override
    public void onActivityResult(ActivityResult result) {
        if (result.getResultCode() == Activity.RESULT_OK) {
            baseDocumentTreeUri = Objects.requireNonNull(result.getData()).getData();
            final int takeFlags = (Intent.FLAG_GRANT_READ_URI_PERMISSION | Intent.FLAG_GRANT_WRITE_URI_PERMISSION);

            // take persistable Uri Permission for future use
            context.getContentResolver().takePersistableUriPermission(result.getData().getData(), takeFlags);
            SharedPreferences preferences = context.getSharedPreferences("com.example.fileutility", Context.MODE_PRIVATE);
            preferences.edit().putString("filestorageuri", result.getData().getData().toString()).apply();
        } else {
            Log.e("FileUtility", "Some Error Occurred : " + result);
        }
}

Step 3: Write CSV content into a file.

public void writeFile(String fileName, String content)  {
        try {
            DocumentFile directory = DocumentFile.fromTreeUri(context, baseDocumentTreeUri);
            DocumentFile file = directory.createFile("text/*", fileName);
            ParcelFileDescriptor pfd = context.getContentResolver().openFileDescriptor(file.getUri(), "w");
            FileOutputStream fos = new FileOutputStream(pfd.getFileDescriptor());
            fos.write(content.getBytes());
            fos.close();
        } catch (IOException e) {
            
        }
}

For more explanation, you can read "How to Save a file in Shared Storage in Android 10 or Higher" or Android official documentation.

Create CSV file with the right permissions

1 Answers1