ImageView returns to Null set by the Drawable files in Android

Question

I know this is a common question to ask but yet I have a problem which the ImageView returns to null. I just want to know if it is possible to call an xml file from the drawable and convert it to Byte []. One thing it returns a null because I didn't declare ImvTempCashCard = findViewById(R.id.ImageView);.Is there any other way to call drawable image without using ImageView?.I just want to set temporary value to ImvTempCashCard which assign image from the drawable files, It is necessary to use setBackgroundResource to ImageView?

error

Attempt to invoke virtual method 'void android.widget.ImageView.setBackgroundResource(int)' on a null object reference

Source

ImageView ImvTempCashCard;

ImvTempCashCard.setBackgroundResource(R.drawable.ic_creditcard);
Bitmap bitmap = ((BitmapDrawable)ImvTempCashCard.getDrawable()).getBitmap();
ImvTempCashCard.setImageBitmap(Bitmap.createScaledBitmap(bitmap, 120, 120, false));
ByteArrayOutputStream stream = new ByteArrayOutputStream();
byte [] byteimage = stream.toByteArray();
//byteimage = returns to null

Latest update:

Actually This will view and add to my GridView, while looping the query, the condition is, when the blob image is null then it will replace the drawable files image. Did I implement it correctly?

  try {
        Cursor cursor = MainActivity.sqLiteHelper.getData("SELECT id,cash_card_actual_no,hh_number,series_number,cc_image, id_image, cash_card_scanned_no FROM CgList");
        list.clear();

        while (cursor.moveToNext()) {
            int id = cursor.getInt(0);
            byte[] CashCardImage = cursor.getBlob(4);

            if (CashCardImage.length ==1){

                Bitmap bitmap = BitmapFactory.decodeResource(getApplicationContext().getResources(),R.drawable.ic_creditcard);
                ByteArrayOutputStream stream = new ByteArrayOutputStream();
                byte [] z = stream.toByteArray();
                CashCardImage = z;

            }
            list.add(new Inventory(cashCardNumber, CashCardImage,id));
        }
        adapter.notifyDataSetChanged();
    }

Adapter inside onCreate

    @Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_inventory_list);
    
    gridView = (GridView) findViewById(R.id.gridView);
    list = new ArrayList<>();
    adapter = new InventoryListAdapter(this, R.layout.activity_inventory_items, list);
    gridView.setAdapter(adapter);

InventoryListAdapter class

public class InventoryListAdapter extends BaseAdapter {

private Context context;
private  int layout;
private ArrayList<Inventory> foodsList;

public InventoryListAdapter(Context context, int layout, ArrayList<Inventory> foodsList) {
    this.context = context;
    this.layout = layout;
    this.foodsList = foodsList;
}

@Override
public int getCount() {
    return foodsList.size();
}
@Override
public Object getItem(int position) {
    return foodsList.get(position);
}

@Override
public long getItemId(int position) {
    return position;
}

private class ViewHolder{
    ImageView imageView;
}

@Override
public View getView(int position, View view, ViewGroup viewGroup) {

    View row = view;
    ViewHolder holder = new ViewHolder();
    if(row == null){
        LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        row = inflater.inflate(layout, null);

        holder.imageView = (ImageView) row.findViewById(R.id.imgFood);
        row.setTag(holder);
    }
    else {
        holder = (ViewHolder) row.getTag();
    }
    Inventory inventory = foodsList.get(position);
    byte[] foodImage = inventory.getImage();
    Bitmap bitmap = BitmapFactory.decodeByteArray(foodImage, 0, foodImage.length);
    holder.imageView.setImageBitmap(bitmap);
    return row;
}
}

Answer 1

Your goal is to display a placeholder image from drawable in a grid view when the image is not found from the database. You can put all the logic inside the getView() in the adapater. Check if the image data does not exist, then call setImageResource instead of setImageBitmap.

First, no need to do any extra steps when constructing the list

Cursor cursor = MainActivity.sqLiteHelper.getData("SELECT id,cash_card_actual_no,hh_number,series_number,cc_image, id_image, cash_card_scanned_no FROM CgList");
list.clear();

while (cursor.moveToNext()) {
    int id = cursor.getInt(0);
    byte[] CashCardImage = cursor.getBlob(4);
    list.add(new Inventory(cashCardNumber, CashCardImage,id));
}
adapter.notifyDataSetChanged();

Then change your getView() like this:

@Override
public View getView(int position, View view, ViewGroup viewGroup) {

    View row = view;
    ViewHolder holder = new ViewHolder();
    if(row == null){
        LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        row = inflater.inflate(layout, null);

        holder.imageView = (ImageView) row.findViewById(R.id.imgFood);
        row.setTag(holder);
    }
    else {
        holder = (ViewHolder) row.getTag();
    }
    Inventory inventory = foodsList.get(position);
    byte[] foodImage = inventory.getImage();
    if(foodImage.length > 1)
    {
        Bitmap bitmap = BitmapFactory.decodeByteArray(foodImage, 0, foodImage.length);
        holder.imageView.setImageBitmap(bitmap);
    }
    else{
        holder.imageView.setImageResource (R.drawable.ic_creditcard)
    }
    
    return row;
}

Tips: Whenever you want to display something to the view that don't need extra processing, try to do it as directly as possible. Avoid extracting the data, storing the data somewhere and pass it around etc. Just get the data to the view you want to display directly.