游标仅返回一个值，而不是所有值

Question

I have encountered a problem in my Android application. I want to retrieve all values of a column, but I am only getting one of the values. I have tried everything, but I could still not find a solution. Here is my code in my database:

 public Cursor returnAllColumns() {
    Cursor cursor = mDb.query(FTS_VIRTUAL_TABLE,
            new String[] {KEY_ROWID,
                    KEY_NAME,
            KEY_CUSTOMER, PROTEIN, TOTAL_CARB}
            , null, null, null, null, null);
if (cursor != null) {
        cursor.moveToNext();
}
    return cursor;
}

Here is my code in another class where it shows a toast with all the values.

mDbHelper = new DBAdapter(DatabaseFiller.this);
                    mDbHelper.open();
                    Cursor c = mDbHelper.returnAllColumns();

                    String protein = c.getString(c.getColumnIndexOrThrow("protein"));

                    Toast.makeText(getApplicationContext(), protein, Toast.LENGTH_SHORT).show();

All I am getting is Protein = 0 . What I should be getting is 0, 0, 0, 0, 0, 0,... . I don't know what I am doing wrong here. In my ListView, I got it right. It worked perfectly there. Here is my ListView code:

mListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                // Get the cursor, positioned to the corresponding row in the result set
                cursor = (Cursor) mListView.getItemAtPosition(position);
                //mListView.setItemChecked(position, true);
                // Get the state's capital from this row in the database.
                String name = cursor.getString(cursor.getColumnIndexOrThrow("customer"));
                String caloriescursor = cursor.getString(cursor.getColumnIndexOrThrow("name"));
                String totalfat = cursor.getString(cursor.getColumnIndexOrThrow("address"));
                String satfatcursor = cursor.getString(cursor.getColumnIndexOrThrow("city"));
                String state = cursor.getString(cursor.getColumnIndexOrThrow("state"));
                String zipCode = cursor.getString(cursor.getColumnIndexOrThrow("zipCode"));

And that returns a Toast with a bunch of values. Any help regarding this problem would be appreciated.

Answer 1

You need to loop over the cursor if the cursor is returning more than one row, and build your output in the loop.

Keep calling c.moveToNext() until it returns false.

Answer 2

In getAllColumns() , your query statement is correct. It does in fact fetch all columns. The if statement that follows simply points it to the first result. Then you are returning the cursor while it is pointed to the first result. You should take out the if statement because it doesn't do anything useful.

When trying to show the toast, you want something like this:

Cursor c = mDbHelper.returnAllColumns();
ArrayList<String> protein = new ArrayList<>();
while (c.moveToNext()) {
    protein.add(c.getString(c.getColumnIndexOrThrow("protein")));
}
Toast.makeText(getApplicationContext(), TextUtils.join(", ", protein), Toast.LENGTH_SHORT).show();

Answer 3

I had the same problem until I did this:

if (!cursor.moveToFirst()) {
    Log.d(LOG_TAG, "=== cursor not moveToFirst() ===");

    return null;
}

Log.d(LOG_TAG, "=== reading cursor of getAll() ===");
Log.d(LOG_TAG, String.valueOf(cursor));

List<Trip> trips = new ArrayList<>();
while (!cursor.isAfterLast()) {
    trips.add(cursorToTrip(cursor));

    cursor.moveToNext();
}

The cursor.moveToNext() will never check the first element. So I check in the course is not in the last one and then I add the object and move to the next one.

That's it! :)