java.lang.NullPointerException in Blob

问题:

I using java.sql.Blob object to save images in mySql. When i try insert object in database i have exception "Java.lang.NullPointerException"

Here is my code :

@Override
protected Object doInBackground(Object... arg0) {

            try {
Bitmap photo = BitmapFactory.decodeResource(getResources(), R.drawable.icon);

            Users user = new Users(); 
            user.setName("haris");

Next code get me exception.

try {
            Blob blo = null;
            blo.setBytes(1, getBytes(photo));

       } catch (Exception e) {
       System.out.println("Error:"+e.toString()); //There is my Exception
       }

/

    if (Korisnik_servis.Registracija(user)){ // Call my REST services
    System.out.println("Registration succesful");           
    }
        else 
    {
    System.out.println("Registration  not succesful");
    }


            } catch (Exception e) {


                System.out.println("Error:"+e.toString());
            }



            return null;
        }

Function for convert Bitmap to byte []

public static byte[] getBytes(Bitmap bitmap) {
        ByteArrayOutputStream stream = new ByteArrayOutputStream();
        bitmap.compress(CompressFormat.PNG, 0, stream);
        return stream.toByteArray();
    }

My question is: how to successfully initialize Blob object.

回答1:

I am using this piece of code to store bitmaps in blobs (converted from drawable):

db = this.getWDB();
    ContentValues values = new ContentValues();

         Drawable d = model.getAppIcon();
    BitmapDrawable bitDw = ((BitmapDrawable) d);
    Bitmap bitmap = bitDw.getBitmap();
    ByteArrayOutputStream stream = new ByteArrayOutputStream();
    bitmap.compress(Bitmap.CompressFormat.PNG, 100, stream);
    byte[] imageInByte = stream.toByteArray();

    values.put(COLUMN_ICON_BLOB, imageInByte); 

    db.insert(TABLE_APPS, null, values);
    db.close();

and to retrieve it from database this method is used

    public static Drawable convertByteArrayToDrawable( byte[] byteArrayToBeCOnvertedIntoBitMap) {

    Bitmap bitMapImage = BitmapFactory.decodeByteArray(
            byteArrayToBeCOnvertedIntoBitMap, 0,
            byteArrayToBeCOnvertedIntoBitMap.length);

    return new  BitmapDrawable(bitMapImage);
}

回答2:

You have exception because Blob is an interface and setBytes is an abstract method. Check this link how to store Image as blob in Sqlite & how to retrieve it?