How to transfer a picture in the BLOB format of the database field from the service to the ImageView of the android device?

Question

Java

Hello.
I am making the following application:
There is a certain SQlite database on the server, it has a table, and in the table field there is a picture (code below):

CREATE TABLE test (rowid INTEGER PRIMARY KEY AUTOINCREMENT, num1 REAL, num2 REAL, num3 REAL, num4 REAL, picture BLOB);
INSERT INTO test (num1, num2, num3, num4, picture) VALUES(1.1, 1.2, 1.3, 1.4, readfile('download.png'));

Tomcat is on the server, which selects this image from the database through the service and returns it in Json format:

private JSONArray getDbDataInJsonArrayFormat() {
        String sql = "SELECT rowid, num1, num2, num3, num4, picture FROM test";

        try (Connection conn = this.connect();
             Statement stmt = conn.createStatement();
             ResultSet rs = stmt.executeQuery(sql)) {

            JSONArray jsonResult = new JSONArray();

            while (rs.next()) {
                JSONObject jsonRow = new JSONObject();
                jsonRow.accumulate("picture", rs.getString("picture"));
                jsonResult.put(jsonRow);
            }
            return jsonResult;
        } catch (SQLException e) {
            LOG.error(e.getMessage());
            return null;
        }
    }

Android connects to the service, downloads Json, puts the image in its database:

try {
            db.beginTransaction();

            for (int i = 0; i < response.length(); i++) {
                JSONObject jsonRow = response.getJSONObject(i);

                String picture = jsonRow.getString("picture");
                ContentValues values = new ContentValues();
                values.put(Test.PICTURE, picture);

                db.insert(TEST, null, values);
            }

            db.setTransactionSuccessful();
        } catch (Exception e) {
            Log.w("Error: ", e);
        } finally {
            db.endTransaction();
        }

Then I fetch a row from the database, try to form a BLOB, but nothing happens:

public Cursor getAllDataFromTestTable() {
        SQLiteDatabase db = mDbOpenHelper.getWritableDatabase();
        String table =  TEST;
        
        Cursor c = db.query(table, null,
                null, null, null, null, null);
        if (c != null) {
            c.moveToFirst();
        }
        return c;
    }

public static List<ContentValues> getResultStringListAndClose(Cursor c) {
        final List<ContentValues> resultStringList = getAllDataFromDB(c);
        closeCursor(c);
        return resultStringList;
    }

private void onDataLoadedFromDb(Cursor c) {
    List<ContentValues> resList = DbUtils.getResultStringListAndClose(c);

    for (int i = 0; i < resList.size(); ++i) {
        ContentValues rowValues = resList.get(i);


        // picture
        ImageView picture = new ImageView(this);
        byte[] encodeByte = rowValues.getAsByteArray(DbContract.Test.PICTURE);
        Bitmap bitmap = BitmapFactory.decodeByteArray(encodeByte, 0, encodeByte.length);
        picture.setImageBitmap(Bitmap.createScaledBitmap(bitmap, picture.getWidth(),
               picture.getHeight(), false));

    }
}

The bitmap variable turns out to be null.
Tell me, please, what is the error here or how to do my task correctly?

Answer 1

All this is crap. Do not store pictures in the database. Store files and paths to them. Especially on Android, the cursor size is limited, and there will be uploads on the main thread, which means brakes. Give the path in json too. Load in Android using special libs. Glide, picasso, fresco, something like that.