Android sqlite更新blob后无法读取

Question

    public void save(Bill aBill) {
        ContentValues values = new ContentValues();
        values.put(DatabaseHelper.BILL_NAME_COLUMN, aBill.getName());
        values.put(DatabaseHelper.BILL_DUE_DATE_COLUMN, getContentValue(aBill.getDueDate()));
        values.put(DatabaseHelper.BILL_IMAGE_COLUMN, aBill.getImage());
        if (!aBill.isPersistent()) {
            aBill.setId(database.insert(DatabaseHelper.BILL_TABLE, null, values));
            aBill.setPersistent(true);
        } else {
            database.update(DatabaseHelper.BILL_TABLE, values, DatabaseHelper.BILL_ID_COLUMN + "=?", new String[]{String.valueOf(aBill.getId())});
        }
    }

    // fails after updating the blob
    public Bill get(long id) {
        Cursor cursor = database.query(DatabaseHelper.BILL_TABLE,
                new String[]{DatabaseHelper.BILL_ID_COLUMN, DatabaseHelper.BILL_NAME_COLUMN, DatabaseHelper.BILL_DUE_DATE_COLUMN, DatabaseHelper.BILL_IMAGE_COLUMN}, "id = ?", new String[] {String.valueOf(id)}, null,
                null, DatabaseHelper.BILL_DUE_DATE_COLUMN);
        Bill bill = null;
        while (cursor.moveToNext()) {
            bill = new Bill();
            bill.setPersistent(true);
            bill.setId(cursor.getLong(cursor.getColumnIndex(DatabaseHelper.BILL_ID_COLUMN)));
            bill.setName(cursor.getString(cursor.getColumnIndex(DatabaseHelper.BILL_NAME_COLUMN)));
            bill.setDueDate(getDate(cursor.getString(cursor.getColumnIndex(DatabaseHelper.BILL_DUE_DATE_COLUMN))));
            bill.setImage(cursor.getBlob(cursor.getColumnIndex(DatabaseHelper.BILL_IMAGE_COLUMN)));

        }
        cursor.close();
        return bill;
    }

    //works fine after updating the blob
    public List findAll() {
        List bills = new ArrayList();
        Cursor cursor = database.query(DatabaseHelper.BILL_TABLE,
                new String[]{DatabaseHelper.BILL_ID_COLUMN, DatabaseHelper.BILL_NAME_COLUMN, DatabaseHelper.BILL_DUE_DATE_COLUMN}, null, null, null,
                null, DatabaseHelper.BILL_DUE_DATE_COLUMN);

        while (cursor.moveToNext()) {
            Bill bill = new Bill();
            bill.setPersistent(true);
            bill.setId(cursor.getLong(cursor.getColumnIndex(DatabaseHelper.BILL_ID_COLUMN)));
            bill.setName(cursor.getString(cursor.getColumnIndex(DatabaseHelper.BILL_NAME_COLUMN)));
            bill.setDueDate(getDate(cursor.getString(cursor.getColumnIndex(DatabaseHelper.BILL_DUE_DATE_COLUMN))));

            bills.add(bill);
        }
        cursor.close();
        return bills;
    }

java.lang.IllegalStateException: Couldn't read row 0, col 0 from CursorWindow.  Make sure the Cursor is initialized correctly before accessing data from it.
at android.database.CursorWindow.nativeGetLong(Native Method)
at android.database.CursorWindow.getLong(CursorWindow.java:511)
at android.database.AbstractWindowedCursor.getLong(AbstractWindowedCursor.java:75)
at net.rka.android.billreminder.BillDao.get(BillDao.java:106)

我怀疑连续更新一个blob会损坏数据库。
有人遇到过类似的问题吗？如果是的话，你是怎么解决的？

Answer 1

您的问题很可能是由于图像的大小和一个怪癖，因为没有更好的术语，您可以存储大的blob而没有问题，但由于Android的光标窗口的大小限制为2M，您可能无法检索blob。这有时会与一些SQLiteDatabase/Cursor（本例中是CursorgetBlob()或它的底层方法）方法复合，这些方法基本上隐藏了底层故障，以便提供通常更简单的开发体验。

如果您使用了SQLiteDatabaseDatabaseutils.dumpCursor，这可能会突出显示SQLiteDatabase查询方便方法可能隐藏的问题。所以加上：-

DatabaseUtils.dumpCursor(cursor); //<<<< ADDED
while (cursor.moveToNext()) { ........

可能提供线索。

我能想到3个选择：-

1. 不是将文件存储为BLOB，而是将文件存储为磁盘上的文件，并将路径存储在数据库中。
2. 显著减小图像的大小。
3. 研究如何使用C++和本机SQLIte3库将Blob检索到适当大小的容器中。