I can not update an item list in the database room and add the item to the favorites list-CodePudding

I can not set an isfavorites value by clicking Add to Favorites . Android Studio displays a null pointer exception for ringTonesDao . I do not know how to fix this error. On the other hand, because ringTonesDao is an interface, if I set its value to new RingTonesDao, I have to set all its functions.

this is RingTonesAdapter

//Imports and Package name
public class RingTonesAdapter extends 
RecyclerView.Adapter<RingTonesAdapter.ringTonesViewHolder> {
private List<RingTones> ringTonesList;
RingTonesDao ringTonesDao; //  <--This is null in logcat


public RingTonesAdapter(List<RingTones> ringTonesList) {
    this.ringTonesList = ringTonesList;
}

@NonNull
@Override
public ringTonesViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
    View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.actv_main_list, 
 parent, false);
    return new ringTonesViewHolder(view);
}

@Override
public void onBindViewHolder(@NonNull ringTonesViewHolder holder, int position) {
    //Set RingTone name to TextView
    //Set RingTone Btn
    //Set Alarm Btn
    //Set Notification Btn
    //Add To Favorites Btn

    if (ringTonesList.get(position).isFavorite()) {
        holder.btn_addToFavorites.setImageResource(R.drawable.ic_favorites);
    } else {
        holder.btn_addToFavorites.setImageResource(R.drawable.ic_addtofavorites);
    }
   

   holder.btn_addToFavorites.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            try {
                Long id = ringTonesList.get(position).getId();
                ringTonesDao.update(true,id);
            }catch (NullPointerException e){
                Toast.makeText(v.getContext(),"Null Pointer 
     Exception",Toast.LENGTH_LONG).show();
            }
        }
    });

    //Set Play Btn

    //ringTonesViewHolder and count items

and this is RingTonesDao

//import and package

 @Dao
 public interface RingTonesDao {

@Insert
Long add(RingTones ringTones);

@Delete
int delete(RingTones ringTones);

@Query("SELECT * FROM tbl_ringtones")
List<RingTones> getRingTones();

@Query("SELECT * FROM tbl_ringtones WHERE favorites>0 ")
List<RingTones> favorites();

@Query("DELETE FROM tbl_ringtones")
void deleteAll();

@Query("UPDATE tbl_ringtones SET favorites=:favorites WHERE id=:id")
int update (Boolean favorites ,Long id);

 }

CodePudding user response：

You need to do something like this

DatabaseClient.getInstance(v.getContext()).getAppDatabase()
                    .RingTonesDao()
                    .update(true,id);

read more how to use Rom database : from this example

also there is a difference between Boolean and boolean in Java,
in your case try to use `boolean` instead `Boolean` in your update function.