Files copied are corrupted

Question

I am trying to transfer some files in Android.

I am having the list of files and then I transfer them to the desired location.

The type of file may be anything Images, Videos, Audios, Gifs, PowerPoint, Word etc.

The size of the list of files is around 100.

This is the code which I am using to transfer files

public static boolean copy(File copy, String directory, Context con) {
   static FileInputStream inStream = null;
   static OutputStream outStream = null;
   DocumentFile dir = getDocumentFileIfAllowedToWrite(new File(directory), con);
   String mime = "";
   DocumentFile copy1 = dir.createFile(mime, copy.getName());

   try {
      inStream = new FileInputStream(copy);
      outStream = con.getContentResolver().openOutputStream(copy1.getUri());
      byte[] buffer = new byte[16384];
      int bytesRead;
      while ((bytesRead = inStream.read(buffer)) != -1) {
         outStream.write(buffer, 0, bytesRead);
      }
   }
   catch (FileNotFoundException e) {
      e.printStackTrace();
   } catch (IOException e) {
      e.printStackTrace();
   } finally {
      try {
         inStream.close();
         outStream.close();
         return true;
      } catch (IOException e) {
         e.printStackTrace();
      }
   }
   return false;
}

Can any one please explain the reason of file being corrupted after transferring and the precautions which could be taken.

EDIT: This is how I use the function

String from = "/storage/emulated/0/Pictures/IMG.jpg";
String to = "/storage/3096-13FF/Pictures";

Class.copy(from, to, this);

EDIT 2: Original file size is around 1-2 MB on an average. Copied file size = Unknown as this issue has been raised by an user.

This is the method which return a DocumentFile by inputting an path.

 public static DocumentFile getDocumentFileIfAllowedToWrite(File file, Context con) {

List<UriPermission> permissionUris = con.getContentResolver().getPersistedUriPermissions();

for (UriPermission permissionUri : permissionUris) {

    Uri treeUri = permissionUri.getUri();
    DocumentFile rootDocFile = DocumentFile.fromTreeUri(con, treeUri);
    String rootDocFilePath = "SD CARD PATH";
    if (file.getAbsolutePath().startsWith(rootDocFilePath)) {

        ArrayList<String> pathInRootDocParts = new ArrayList<String>();
        while (!rootDocFilePath.equals(file.getAbsolutePath())) {
            pathInRootDocParts.add(file.getName());
            file = file.getParentFile();
        }

        DocumentFile docFile = null;

        if (pathInRootDocParts.size() == 0) {
            docFile = DocumentFile.fromTreeUri(con, rootDocFile.getUri());
        } else {
            for (int i = pathInRootDocParts.size() - 1; i >= 0; i--) {
                if (docFile == null) {
                    docFile = rootDocFile.findFile(pathInRootDocParts.get(i));
                } else {
                    docFile = docFile.findFile(pathInRootDocParts.get(i));
                }
            }
        }
        if (docFile != null && docFile.canWrite()) {
            return docFile;
        } else {
            return null;
        }

    }
}
return null;
 }

I am making the user choose the SD Card Directory using the storage access framework so that I can write to any directory in the SD Card. And then when ever the file has to be transferred I am making the user choose the path using an custom dialog box.

Answer 1

Data is buffered by OtputStream before actual write, and not directly writen to file. And some of data might still remain in this buffer at time you close the file. This is optimisation that improves performance of small writes, it removes lot of latency caused by slow persistent storage device, like hard disk, SD card ....

You need to flush output stream buffer, before closing the file. I think that all data didn’t sync to file. So before closing output, try to flush buffer.

outStream.flush();

And to make sure data is writen to storage device (SD card) from file system cache, (if not implicit done by close() )

outStream.getFD().sync();

By defult, file system writes and reads are cached by operating system. This should not affect you except you remove battery at exact moment after copy()

More about is already explaeined here

I/O concept flush vs sync