How to update listview in Fragment with custom adapter

Question

I am giving product id with barcode scanner. I can add product to listView but when i try to increase or decrease amount of the product. It doesn't update UI. I used Toast message to see weather list is updated, it updates list but doesn't update UI

I have tried to use runOnUiThread() but i couldn't find any solution. How to update UI can you please help me

custom_lisView_row

BaseActivity which keeps MainFragment on it

public class BaseActivity extends AppCompatActivity {

    public static final String MAIN_FRAGMENT = "mainFragment";
    public static final String PRODUCTS = "products";

    FragmentManager fragmentManager;

    Dialog dialog ;

    public static ArrayList<MyProduct>  myProductList = new ArrayList<>();
    public static MyTablet myTablet = new MyTablet();

    Activity mActivity;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_base);

        //Initialize fragment manager
        fragmentManager = getSupportFragmentManager();
  
        fragmentManager.beginTransaction().replace(R.id.fl_BaseActivity, new MainFragment()).commit();

        //Create database
        mDatabase = FirebaseDatabase.getInstance().getReference();

        dialog = new Dialog(this);

        //Runs when i enter product id
        initScanner();
    }

    public void updateMyProductList(MyProduct myProduct){

        for(int i= 0 ; i< myProductList.size() ; i++ ){

            MyProduct temp = myProductList.get(i);

            if (temp.getId().equals(myProduct.getId())) {
                temp.setAmount(temp.getAmount() + myProduct.getAmount());
                myProductList.set(i, temp);
                return;
            }
        }
        myProductList.add(myProduct);
        updateMainFragment();
    }

    private void initScanner() {
      
      mDatabase.child(PRODUCTS).child(finalData).get().addOnCompleteListener(new OnCompleteListener<DataSnapshot>() {
          @Override
          public void onComplete(@NonNull Task<DataSnapshot> task) {

              MyProduct myProduct = task.getResult().getValue(MyProduct.class);
              myProduct.setAmount(1);
              dialog.setContentView(R.layout.custom_product_dialog);
              dialog.getWindow().setBackgroundDrawable(new ColorDrawable(Color.TRANSPARENT));
              dialog.setCancelable(false);

              
              TextView tv_addBasket_product_dialog = dialog.findViewById(R.id.tv_addBasket_product_dialog);
            

              tv_addBasket_product_dialog.setOnClickListener(new View.OnClickListener() {
                  @Override
                  public void onClick(View view) {
                      updateMyProductList(myProduct);
                      dialog.dismiss();
                  }
              });

              dialog.show();
          }
      };
    }
    public void updateMainFragment() {
        if (isExist(MAIN_FRAGMENT)) {
            Fragment fragment = findFragment(MAIN_FRAGMENT);

            ((MainFragment) fragment).updateMyList();
        }

    }

    //Add fragments to BaseActivity
    public void addFragments(Fragment fragment, String tag) {

        fragmentManager.beginTransaction().add(R.id.fl_BaseActivity, fragment, tag).commit();
    }
    //Replace fragments to BaseActivity
    public void replaceFragments(Fragment fragment, String tag) {

        fragmentManager.beginTransaction().replace(R.id.fl_BaseActivity, fragment, tag).commit();
    }

    //Remove fragment from BaseActivity
    public void removeFragment(String tag) {

        Fragment fragmentB = fragmentManager.findFragmentByTag(tag);
        FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
        if (fragmentB != null) {
            fragmentTransaction.remove(fragmentB);
            fragmentTransaction.commit();
        }
    }

    // finds fragment and returns it
    // It may return null first check fragment is exist. use isExist() method
    public Fragment findFragment(String tag) {
        Fragment fragment = fragmentManager.findFragmentByTag(tag);
        return fragment;
    }

    //Check fragment exist in BaseActivity
    public boolean isExist(String tag) {
        Fragment fragmentB = fragmentManager.findFragmentByTag(tag);
        if (fragmentB != null) {
            return true;
        }
        return false;
    }

}

MainFragment

public class MainFragment extends Fragment {
    
    ListView lv_MainFragment;

    public MyProductListAdapter myListAdapter;
    public static ArrayList<MyProduct>  myProductList;

    Activity mActivity;

    @Override
    public void onAttach(Context context) {
        super.onAttach(context);

        mActivity = getActivity();
    }

    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        myProductList = BaseActivity.myProductList;
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_main, container, false);

        lv_MainFragment = view.findViewById(R.id.lv_MainFragment);

        myListAdapter = new MyProductListAdapter(mActivity.getApplicationContext(), R.layout.custom_product_list_row, myProductList);
        lv_MainFragment.setAdapter(myListAdapter);


        return view;
    }

    public void updateMyList() {

        myProductList = BaseActivity.myProductList;
        myListAdapter.notifyDataSetChanged();

    }

}

MyProductListAdapter

public class MyProductListAdapter extends ArrayAdapter<MyProduct> {


    private Context mContext;
    private ArrayList<MyProduct> list;

  
    AppCompatButton acb_DecreaseAmount_productListRow, acb_IncreaseAmount_productListRow;


    public MyProductListAdapter(Context context, int resource, ArrayList<MyProduct> objects) {
        super(context, resource, objects);

        this.mContext = context;
        this.list = objects;
    }

    @Override
    public View getView(int position, @Nullable View convertView, @NonNull ViewGroup parent) {
        View view = convertView;

        if (view == null) {

            LayoutInflater inflater = (LayoutInflater) mContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            view = inflater.inflate(R.layout.custom_product_list_row, parent, false);

        
            tv_ProductAmount_productListRow = view.findViewById(R.id.tv_ProductAmount_productListRow);
        
            acb_DecreaseAmount_productListRow = view.findViewById(R.id.acb_DecreaseAmount_productListRow);
            acb_IncreaseAmount_productListRow = view.findViewById(R.id.acb_IncreaseAmount_productListRow);

            tv_ProductAmount_productListRow.setText(String.valueOf(list.get(position).getAmount()));

            acb_IncreaseAmount_productListRow.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                    double productPrice = list.get(position).getPrice();
                    int productAmount = list.get(position).getAmount();
                    productAmount++;

                    list.get(position).setAmount(productAmount);

                    Toast.makeText(mContext, String.valueOf(productAmount), Toast.LENGTH_SHORT).show();

                    tv_ProductAmount_productListRow.setText(String.valueOf(list.get(position).getAmount()));
                }
            });

            acb_DecreaseAmount_productListRow.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {

                    int productAmount = list.get(position).getAmount();

                    if (productAmount > 1) {
                        double productPrice = list.get(position).getPrice();

                        productAmount--;

                        list.get(position).setAmount(productAmount);

                        Toast.makeText(mContext, String.valueOf(productAmount), Toast.LENGTH_SHORT).show();

                        tv_ProductAmount_productListRow.setText(String.valueOf(list.get(position).getAmount()));      
                    }
                }
            });

        }

        return view;
    }

}

Answer 1

Hej Metehan,

your use case sounds perfect for a RecyclerView with a ListAdapter. You just submit a new list of products to the adapter and it will handle the updating and notifying for you.