片段更改后无法显示Listview

Question

我有NavigationActivitiy有多个片段。

在第一个片段（MainFragment）中，有两个内部片段（ProductDisplayFragment，PaymentFragment）相互通信。在ProductDisplayFragment中选择项目时，所选产品将添加到ArrayList中，其中项目的ArrayList显示在PaymentFragment的ListView中。

但是，一旦我切换到另一个NavigationActivity片段，然后切换回MainFragment，ProductDisplayFragment仍然能够成功地将项目添加到PaymentFragment中的ArrayList（从logcat检查），但ListView不再显示其视图。

这是我的代码：

ProductDisplayFragment.java

public class ProductDisplayFragment extends Fragment {

    private static final String MESSAGE_ERROR_IMPLEMENTATION = "Implementation of sendProduct method required";

    private GridView gridView;
    private ProductGridAdapter productAdapter;
    private OnProductSelectedListener sendProduct;

    public ProductDisplayFragment() {
        // Required empty public constructor
    }

    public interface OnProductSelectedListener {
        void onProductSelected(Product product);
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        View rootView = inflater.inflate(R.layout.fragment_product_display, container, false);

        gridView = (GridView) rootView.findViewById(R.id.gridview);
        productAdapter = new ProductGridAdapter(getActivity(), R.layout.fragment_product_display, getProductList());
        gridView.setAdapter(productAdapter);

        return rootView;
    }

    @Override
    public void onAttach(Activity activity) {
        super.onAttach(activity);

        try {
            sendProduct = (OnProductSelectedListener) activity;
        } catch (ClassCastException e) {
            throw new ClassCastException(MESSAGE_ERROR_IMPLEMENTATION);
        }
    }
}

PaymentFragment.java

public class PaymentFragment extends Fragment {

    public PaymentFragment() {

    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        if(savedInstanceState == null) {
            productList = new ArrayList<>();
        } else {
            productList = savedInstanceState.getParcelableArrayList(KEY_PRODUCTLIST);
            updateListView();
        }
    }

    @Override
    public void onSaveInstanceState(Bundle outState) {
        super.onSaveInstanceState(outState);
        outState.putParcelableArrayList(KEY_PRODUCTLIST, productList);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        View rootView = inflater.inflate(R.layout.fragment_payment, container, false);

        listView = (ListView) rootView.findViewById(android.R.id.list);
        paymentAdapter = new PaymentListAdapter(getActivity(), R.layout.fragment_payment, productList);
        listView.setAdapter(paymentAdapter);

        voidButton = (LinearLayout) rootView.findViewById(R.id.button_void);
        saveButton = (LinearLayout) rootView.findViewById(R.id.button_save);
        noteButton = (LinearLayout) rootView.findViewById(R.id.button_note);
        discountButton = (LinearLayout) rootView.findViewById(R.id.button_discount);
        payButton = (LinearLayout) rootView.findViewById(R.id.button_pay);
        amountSubtotal = (TextView) rootView.findViewById(R.id.amount_subtotal);
        amountDiscount = (TextView) rootView.findViewById(R.id.amount_discount);
        amountTotal = (TextView) rootView.findViewById(R.id.amount_total);

        setDefaultAmount();
        getFirstProduct();
        buttonsOnClick();

        return rootView;
    }

    /*
     * This method retrieves product from fragment and refresh the listview every time a new product is added into listview
     */
    public void getProduct(Product product) {

        Log.d(CLASS_NAME, "Received subsequent product" + product.getName());

        updateProductInfo(product);
        updateListView();

        double discount = Double.parseDouble(finalDiscount);
        calculator.setDiscount(discount);
        calculator.addAmount(product, currentMode);

        amountSubtotal.setText(DOLLAR + String.format(PLACEHOLDER, calculator.getSubTotal()));
        amountDiscount.setText(DOLLAR + String.format(PLACEHOLDER, calculator.getDiscountAmount()));
        amountTotal.setText(DOLLAR + String.format(PLACEHOLDER, calculator.getTotal()));
    }

    private void updateProductInfo(Product product) {
        // Only add product if it does not exist in hashset, else increment quantity number
        if(productHash.contains(product.getBarcode())) {
            int productIndex = productList.indexOf(product);
            product.setQuantity(product.getQuantity() + 1);
            if(productIndex != -1) {
                productList.set(productIndex, product);
            }
        } else {
            product.setQuantity(1);
            productList.add(0, product);
            productHash.add(product.getBarcode());
        }
    }

    private void getFirstProduct() {
        Bundle arguments = getArguments();
        if (arguments != null) {
            Product product = (Product) arguments.getSerializable(KEY_PRODUCT);
            getProduct(product);
            if(product != null) {
                Log.d(CLASS_NAME, "Received subsequent product" + product.getName());
            }
        }
    }

 private void updateTextView () {
        amountSubtotal.setText(DOLLAR + String.format(PLACEHOLDER, calculator.getSubTotal()));
        amountDiscount.setText(DOLLAR + String.format(PLACEHOLDER, calculator.getDiscountAmount()));
        amountTotal.setText(DOLLAR + String.format(PLACEHOLDER, calculator.getTotal()));
        updateListView();
    }

    private void updateListView() {
        Log.d(CLASS_NAME, "Update listview: " + productList.size());
        paymentAdapter = new PaymentListAdapter(getActivity(), R.layout.fragment_payment, productList);
        paymentAdapter.notifyDataSetChanged();
        listView.setAdapter(paymentAdapter);
    }

}