Message is sent after a long time, and some times it is never sent.

ListView list;

public static final String TAG = ChooseFriendsActivity.class.getSimpleName();

protected List<ParseUser> mFriends;
protected ParseRelation<ParseUser> mFriendsRelation;
protected ParseUser mCurrentUser;
protected MenuItem mSendMenuItem;
protected Uri mMediaUri;
protected String mFileType;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_choose_friends);

    list = (ListView) findViewById(R.id.choose_friends_list);
    list.setChoiceMode(ListView.CHOICE_MODE_MULTIPLE);

    mMediaUri = getIntent().getData();
    mFileType = getIntent().getExtras().getString(ParseConstants.KEY_FILE_TYPE);
}

@Override
public void onResume() {
    super.onResume();

    mCurrentUser = ParseUser.getCurrentUser();
    mFriendsRelation = mCurrentUser.getRelation(ParseConstants.KEY_FRIENDS_RELATION);

    ParseQuery<ParseUser> query = mFriendsRelation.getQuery();
    query.addAscendingOrder(ParseConstants.KEY_USERNAME);
    query.findInBackground(new FindCallback<ParseUser>() {
        @Override
        public void done(List<ParseUser> friends, final ParseException e) {

            if (e == null) {
                mFriends = friends;

                String[] usernames = new String[mFriends.size()];
                int i = 0;
                for (ParseUser user : mFriends) {
                    usernames[i] = user.getUsername();
                    i++;
                }
                ArrayAdapter<String> adapter = new ArrayAdapter<String>(
                        list.getContext(),
                        android.R.layout.simple_list_item_checked,
                        usernames);
                list.setAdapter(adapter);
                list.setOnItemClickListener(new AdapterView.OnItemClickListener() {
                    @Override
                    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {

                        if (list.getCheckedItemCount() > 0) {
                            mSendMenuItem.setVisible(true);
                        } else {
                            mSendMenuItem.setVisible(false);
                        }
                    }
                });
            } else {
                Log.e(TAG, e.getMessage());
                AlertDialog.Builder builder = new AlertDialog.Builder(ChooseFriendsActivity.this);
                builder.setTitle(R.string.error_title);
                builder.setMessage(e.getMessage());
                builder.setPositiveButton(android.R.string.ok, null);

                AlertDialog dialog = builder.create();
                dialog.show();
            }
        }
    });
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.menu_choose_friends, menu);
    mSendMenuItem = menu.getItem(0);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();

    //noinspection SimplifiableIfStatement
    if (id == R.id.action_send) {
        ParseObject message = createMessage();
        if (message == null) {
            AlertDialog.Builder builder = new AlertDialog.Builder(this);
            builder.setMessage("There was something wrong with the file selected. Please select another file.")
                    .setTitle("We're Sorry!")
                    .setPositiveButton(android.R.string.ok, null);
            AlertDialog dialog = builder.create();
            dialog.show();
        } else {
            send(message);
            finish();
        }
        return true;
    }

    return super.onOptionsItemSelected(item);
}

protected ParseObject createMessage() {
    ParseObject message = new ParseObject(ParseConstants.CLASS_MESSAGES);
    message.put(ParseConstants.KEY_SENDER_ID, ParseUser.getCurrentUser().getObjectId());
    message.put(ParseConstants.KEY_SENDER_NAME, ParseUser.getCurrentUser().getUsername());
    message.put(ParseConstants.KEY_RECIPIENT_IDS, getRecipientIds());
    message.put(ParseConstants.KEY_FILE_TYPE, mFileType);

    byte[] fileBytes = FileHelper.getByteArrayFromFile(this, mMediaUri);

    if (fileBytes == null) {
        return null;
    } else {
        if(mFileType.equals(ParseConstants.TYPE_IMAGE)) {
            fileBytes = FileHelper.reduceImageForUpload(fileBytes);
        }

        String fileName = FileHelper.getFileName(this, mMediaUri, mFileType);
        ParseFile file = new ParseFile(fileName, fileBytes);
        message.put(ParseConstants.KEY_FILE, file);

        return message;
    }
}

protected ArrayList<String> getRecipientIds() {
    ArrayList<String> recipientIds = new ArrayList<String>();
    for (int i = 0; i < list.getCount(); i++) {
        if (list.isItemChecked(i)) {
            recipientIds.add(mFriends.get(i).getObjectId());
        }
    }
    return recipientIds;
}

protected void send(ParseObject message) {
    message.saveInBackground(new SaveCallback() {
        @Override
        public void done(ParseException e) {
            if (e == null) {
                // success!
                Toast.makeText(ChooseFriendsActivity.this, "Message sent!", Toast.LENGTH_LONG).show();
            }
            else {
                AlertDialog.Builder builder = new AlertDialog.Builder(ChooseFriendsActivity.this);
                builder.setMessage("There was an error sending your message. Please try again.")
                        .setTitle("We're Sorry!")
                        .setPositiveButton(android.R.string.ok, null);
                AlertDialog dialog = builder.create();
                dialog.show();
            }
        }
    });
}