Question

Working on figuring out my NullPointerException within my custom simplecursoradapter when trying to refresh the data in my view. When using SimpleCursorAdapter you cannot use NotifyDataSetChanged() so I need to create a new adapter and I am having difficulty passing on the data required.

public class DxSimpleCursorAdapter extends SimpleCursorAdapter {
Context context;
Activity activity;
DxDbAdapter dbh;
DxSimpleCursorAdapter adapter;
ListView lv;

protected String subcategory;

public DxSimpleCursorAdapter(Context context, int layout, Cursor c, String[] from, int[] to, String param) {
    super(context, layout, c, from, to);
    this.context=context;
    this.activity=(Activity) context;
    subcategory = param;
}

public DxSimpleCursorAdapter(Context context, int layout, Cursor c, String[] from, int[] to) {
    super(context, layout, c, from, to);
    this.context=context;
    this.activity=(Activity) context;
}

@Override
public View newView(Context context, Cursor cursor, ViewGroup parent) {
    LayoutInflater inflater = LayoutInflater.from(context);
    View row = inflater.inflate(R.layout.list_detail, null);
    ViewHolder holder = new ViewHolder();
    holder.image = (ImageView) row.findViewById(R.id.fav);
    holder.diagnosis = (TextView) row.findViewById(R.id.diagnosis);
    holder.code = (TextView) row.findViewById(R.id.code);
    row.setTag(holder);
    return row;
}

class ViewHolder {
    ImageView image;
    TextView diagnosis;
    TextView code;      
}

class Status {
    int status;
    Long id;
}

@Override
public void bindView(View v, Context con, Cursor cursor) {
    ViewHolder holder = (ViewHolder) v.getTag();

    int favstatus = cursor.getInt(cursor.getColumnIndex(DxDbAdapter.FAV));
    Status state = new Status();

    if (favstatus == 1) {
        holder.image.setImageResource(R.drawable.btn_star_on_normal);
        state.status = 1;
    }
    else if (favstatus == 0) {
        holder.image.setImageResource(R.drawable.btn_star_off_normal);
        state.status = 0;
    }

    long id = cursor.getLong(cursor.getColumnIndex(DxDbAdapter.DIAG_ID));
    state.id = id;
    holder.image.setTag(state);
    holder.diagnosis.setText(cursor.getString(cursor.getColumnIndex(DxDbAdapter.DIAG)));
    holder.code.setText(cursor.getString(cursor.getColumnIndex(DxDbAdapter.DIAG_CODE)));

    holder.image.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            Status current_state = (Status) v.getTag();

            ImageView fav = (ImageView) v.findViewById(R.id.fav);
            fav.setImageResource(R.drawable.ic_fav);

            if (current_state.status == 1) {
                Toast toast = Toast.makeText(context,"Update fav status to 1",Toast.LENGTH_SHORT);
                toast.show();
            }
            else if (current_state.status == 0) {
                Toast toast = Toast.makeText(context,"Update fav status to 0",Toast.LENGTH_SHORT);
                toast.show();
            }

                    dbh = new DxDbAdapter(context);
            dbh.open();
            Cursor newCursor = dbh.fetch(1, subcategory);
            String[] columns = new String[] {"diagnosis", "diagcode"};
            int[] to = new int[] {R.id.diagnosis, R.id.code};
            adapter = new DxSimpleCursorAdapter(context, R.layout.list_detail, newCursor, columns, to);
            lv.setAdapter(adapter);
        }
    });
    String diag = cursor.getString(cursor.getColumnIndex(DxDbAdapter.DIAG));
    String code = cursor.getString(cursor.getColumnIndex(DxDbAdapter.DIAG_CODE));
    holder.diagnosis.setText(diag);
    holder.code.setText(code);
}

The issue is with subcategory = getIntent().getStringExtra(“SUBCATEGORY”); and Cursor newCursor = dbh.fetch(1, subcategory); and that I have to reference the Activity that is using the adapter. I guess I am having issues on the correct syntax to reference the Activity so that I don’t get a NullPointerException.

Answer 1

You should really pass in the subcategory from your parent activity since this value will not change while using your adapter (instead of retrieving it every single time you bind to a row)

Ex: from the parent activity you would do something like

String subcategory = getIntent().getStringExtra("SUBCATEGORY"); 
DxSimpleCursorAdapter adapter = DxSimpleCursorAdapter(context, layout, c, from, to, subcategory);
listView.setAdapter(adapter); 

Then obviously you would need to modify the constructor of your adapter so it took that string and then assigned it to your subcategory variable within the adapter