Android - problems with recieving image from SQLite DB

Question

So I get a null pointer exception when trying to recieve image from SQLite database.

Saving image:

    public void insertImage(byte[] imageBytes) {
        ContentValues cv = new ContentValues();
        cv.put(IMAGE, imageBytes);
        mDb.insert(IMAGES_TABLE, null, cv);
    }

Here's my code for recieving the image in the helper class:

    public byte[] retreiveImageFromDB() {
        Cursor cur = mDb.query(true, IMAGES_TABLE, new String[]{IMAGE,},
                null, null, null, null,
                IMAGE_ID + " DESC", "1");
        if (cur.moveToFirst()) {
            byte[] blob = cur.getBlob(cur.getColumnIndex(IMAGE));
            cur.close();
            return blob;
        }
        cur.close();
        return null;
    }

And here's how I try to set the image to ImageView in my activity:

    byte[] image = mImage.retreiveImageFromDB();
    Bitmap bitmap = BitmapFactory.decodeByteArray(image, 0, image.length);
    profileImage.setImageBitmap(bitmap);

What am I doing wrong?

post code for saving it in the DB, you can also use Stetho to check your DB if it's empty or not — elmorabea, Dec 27 '17 at 01:24
Something is strange, your query won't compile becuase there is an extra "," in an array, and what are you using for query, ID? — elmorabea, Dec 27 '17 at 01:38
@elmorabea the `...new String[]{IMAGE,},...` will compile (the last is ignored). i.e. the length of the array will be 1. The query will extract the first row (LIMIT 1) of all rows, who's image column is unique,when ordered by the image_id (which I assume would be an alias of the rowid), — MikeT, Dec 27 '17 at 03:03

score 0 · Answer 1 · edited Jun 20 '20 at 09:12

What am I doing wrong?

You are likely not checking for null being returned from the retreiveImageFromDB method.

Instead of :-

    byte[] image = mImage.retreiveImageFromDB();
    Bitmap bitmap = BitmapFactory.decodeByteArray(image, 0, image.length);
    profileImage.setImageBitmap(bitmap);

You should have something along the lines of :-

    byte[] image = mImage.retreiveImageFromDB();
    if (image != null) {
        Bitmap bitmap = BitmapFactory.decodeByteArray(image, 0, image.length);
        profileImage.setImageBitmap(bitmap);
    } else {
        // Hanlde null here e.g.
        Toast.makeText(this,"Ooops image is null!!!",Toast.LENGTH_SHORT).show();
    }

You may then ask Why is the Cursor empty!

As the query should return at least 1 row if any exist (i.e the restrictions are only uniqueness of the images (blobs) and the number of rows being returned as 1) then there is a likelihood that you may have issues beyond the scope of what is ascertainable from the code given.

You could perhaps change the insertImage method to return the ID of the inserted row, and check this whenever the method is called e.g.

public long insertImage(byte[] imageBytes) { // <<<< changed signature
    ContentValues cv = new ContentValues();
    cv.put(IMAGE, imageBytes);
    return mDb.insert(IMAGES_TABLE, null, cv); // added return
}

Then use something like :-

    if (insertImage(your_image) > 0) {
        Log.d("IMAGEINSERT","Image inserted OK.");
    } else {
        Log.d("IMAGEINSERT","Image was not inserted!!!");
    }

Instead of

    insertImage(your_image);

You could perhaps utilise the utilities provided at this link, these will allow you to inspect the database and tables.

Android - problems with recieving image from SQLite DB

1 Answers1

You may then ask Why is the Cursor empty!