Writing a bitmap to file in the sdcard

Question

I am trying to compress the bitmap into a jpg in my code. I get a nullpointer exception, Please advice

new Thread(new Runnable() {
                    @Override
                    public void run() {
                        Cursor imageCursor=getContentResolver().query(MediaStore.Images.Media.EXTERNAL_CONTENT_URI,new String[]{MediaStore.Video.Media.DATA},MediaStore.Video.Media.DISPLAY_NAME+"=?" ,new String[]{imageTitle},null);
                        imageCursor.moveToFirst();
                        final String imageData=imageCursor.getString(imageCursor.getColumnIndex(MediaStore.Video.Media.DATA));
                        dbConnection connection=new dbConnection(getApplicationContext());
                        SQLiteDatabase db=connection.getWritableDatabase();
                        File imageFile=new File(imageData);
                        File outputFile=new File("mnt/sdcard/Images/hiddenImage.jpg");
                        InputStream is;
                        try 
                        {
                            is = new FileInputStream(imageFile);
                            InputStreamReader inputreader=new InputStreamReader(is);
                            BufferedReader buffReader=new BufferedReader(inputreader);
                            final ByteArrayBuffer buffer=new ByteArrayBuffer(512);
                            int i;
                            while((i=buffReader.read())!=-1)
                            {
                                buffer.append(i);
                            }
                            Bitmap imagefile=BitmapFactory.decodeByteArray(buffer.toByteArray(), 0, buffer.toByteArray().length);
                            OutputStream os=new FileOutputStream("mnt/sdcard/Images/testing.jpg");
                            imagefile.compress(Bitmap.CompressFormat.JPEG, 100, os);
                            os.close();
                        } 
                        catch (FileNotFoundException e) 
                        {
                            e.printStackTrace();
                        } 
                        catch (IOException e) 
                        {
                            e.printStackTrace();
                        }

                    }
                }).start();

Here is the stack trace:

07-09 14:57:48.595: ERROR/AndroidRuntime(5761): FATAL EXCEPTION: Thread-9
07-09 14:57:48.595: ERROR/AndroidRuntime(5761): java.lang.NullPointerException
07-09 14:57:48.595: ERROR/AndroidRuntime(5761):     at com.messageHider.viewImageThumb$1$1.run(viewImageThumb.java:106)
07-09 14:57:48.595: ERROR/AndroidRuntime(5761):     at java.lang.Thread.run(Thread.java:1096)

The exception is thrown where I am trying to compress the bitmap: //::imagefile.compress(Bitmap.CompressFormat.JPEG, 100, os);

Answer 1

If you have a NullPointerException in imagefile.compress(Bitmap.CompressFormat.JPEG, 100, os);, then imagefile must be null. This would occur if BitmapFactory cannot decode the image.

Also:

• Your file-reading algorithm is very inefficient. Please consider reading more than one byte at a time. Or, better still, use decodeStream() rather than decodeByteArray() on BitmapFactory.

• Make sure you have the WRITE_EXTERNAL_STORAGE permission.

• Never hardwire paths, particularly wrong ones, as you are doing here. Use Environment.getExternalStorageDirectory() to get at the root of external storage, then use the appropriate File constructor to assemble a File object pointing to whatever file you want within that directory.

• You do nothing to ensure that the Images/ directory actually exists.