"Invalid argument" when trying to mount my USB

Question

I have Fragment and it uses RecyclerView Adapter with LoaderManager to list items. RecyclerView i use is from this address. I've implemented LoaderManager in Fragment and gave context of its Activity to RecyclerView.

When i add new item to list, it does not refresh and show new item in list. I use same Adapter and structure on another activity and it works good. But here i use RecyclerView with Loader inside Fragment and it does not refresh list when i add item, instead i have to go back(finish fragment) and enter again.

I have 2 tables like this. First I get cursor from student_course table and from that cursor i get student ids of specific class. Then using data of first cursor, i get second cursor from students table which has list of students from same class. Then i send second cursor to adapter. I do below operation on both onCreateView() and onCreateLoader:

String[] projection0 = {
            DatabaseOpenHelper.COL_STUDENT_ID,
            DatabaseOpenHelper.COL_COURSE_ID};
    String selection0=DatabaseOpenHelper.COL_COURSE_ID + "=?";
    String selectionArgs0[]={String.valueOf(courseId)};
    mDataset0=getActivity().getContentResolver().query(StudentContentProvider.CONTENT_URI2, projection0,selection0,selectionArgs0,null);


    if(mDataset0.getCount()!=0) {
        //BATCH
        List<String> selectionList = new ArrayList<String>();
        mDataset0.moveToFirst();

        ...
        String[] projection1 = {
                DatabaseOpenHelper.COLUMN_ID,
                DatabaseOpenHelper.COL_STUDENT_NUMBER,
                DatabaseOpenHelper.COL_STUDENT_NAME,
                DatabaseOpenHelper.COL_STUDENT_CARD_ID,
                DatabaseOpenHelper.COL_STUDENT_COLOR};
        selection1 = selection1.substring(0, selection1.length() - 2) + ")";
        mDataset1 = getActivity().getContentResolver().query(StudentContentProvider.CONTENT_URI1, projection1, selection1, selectionArgs1, null);

    }else{
        mDataset1=null;
    }
...
mAdapter = new studentListAdapter(getActivity(),mDataset1,this);

mDataset1 is students of same class.

1) What might be the problem ? 2) Is there any way to implement LoaderManager class inside

Update 1: When i change selection1 and selectionArgs1 to null, it updates list immediately after i add item. But it shows all students from every class because i didn't specify selection.

Update 2: When i check onLoadFinished() i see that new cursor, after loading new content, is still same as old.

Solution 1

/dev/sdb represents the whole storage device. The individual partitions are addressed by numbers following the device name, e.g. sdb1 is the 1st partition in the storage device sdb. As USB flash drives usually have only one partition, the mount command should be:

mount /dev/sdb1 /mnt/usb

Solution 2

Since this is among the top results I want to share some insight about what happened to me and how I solved it.

My situation is that I'm booting the 18.04 di-based server installer and I want to mount another (virtual) optical disc drive. Which gave me this exact error message.

Observation:

• I'm in a busybox shell, which may behave different than GNU tools.
• I have a different, limited kernel running. While the error message gave no indication and all arguments seemed to be correct I tried loading the filesystem module, iso9660 in my case, with modprobe. Then it worked. So whatever filesystem you are trying to mount, you should check (lsmod?) that the respective filesystem module is loaded to. It's unlikely that the OP was on busybox, but hey questions with not enough context are common and we are trying to solve them.

Solution 3

sda or sdb is just the name of your storage device, if you want to mount it you must enter the partition number too.

mkdir -p /media/usb
mount /dev/sdb1 /media/usb

Comments

[Mouli]

Please add the output of sudo fdisk -l to your question.

[Eric Carvalho]

I think it should be mount /dev/sdb1 /mnt/usb.

[web.learner]

@EricCarvalho You should add that as an answer ;-)

[guntbert]

Instead of adding [solved] to the title please accept the correct/useful answer by clicking on the check-mark beside it.

[hrskrs]

show some code so we can identify the problem

[Jemshit Iskenderov]

@hrskrs some clarifications added