باز کردن gallery از داخل برنامه

این کد چیه دقیقا ؟ چیکار میکنه ؟ من میزارمش ارور میده

REQ_CODE_PICK_IMAGE:  این قسمت کجا مقدار میگیره ؟

protectedvoid onActivityResult(int requestCode,int resultCode,Intent imageReturnedIntent){super.onActivityResult(requestCode, resultCode, imageReturnedIntent);switch(requestCode){case REQ_CODE_PICK_IMAGE:if(resultCode == RESULT_OK){Uri selectedImage = imageReturnedIntent.getData();String[] filePathColumn ={MediaStore.Images.Media.DATA};Cursor cursor = getContentResolver().query(
                               selectedImage, filePathColumn,null,null,null);
            cursor.moveToFirst();int columnIndex = cursor.getColumnIndex(filePathColumn[0]);String filePath = cursor.getString(columnIndex);
            cursor.close();Bitmap yourSelectedImage =BitmapFactory.decodeFile(filePath);}}}

 protected void onActivityResult(int requestCode, int resultCode, 
       Intent imageReturnedIntent) {
    super.onActivityResult(requestCode, resultCode, imageReturnedIntent); 

    switch(requestCode) { 
    case REQ_CODE_PICK_IMAGE:
        if(resultCode == RESULT_OK){  
            Uri selectedImage = imageReturnedIntent.getData();
            String[] filePathColumn = {MediaStore.Images.Media.DATA};

            Cursor cursor = getContentResolver().query(
                               selectedImage, filePathColumn, null, null, null);
            cursor.moveToFirst();

            int columnIndex = cursor.getColumnIndex(filePathColumn[0]);
            String filePath = cursor.getString(columnIndex);
            cursor.close();


            Bitmap yourSelectedImage = BitmapFactory.decodeFile(filePath);
        }
    }