如何在android中将类对象转换为Fragment类对象？

Question

我有一个函数switchContent，它将参数作为片段和字符串。我还有一个ProductListFragment类。我想将ProductlistFragment的对象传递给函数switchContent。我怎么能这样做？

switchContent(pdtListFragment, ProductListFragment.ARG_ITEM_ID);

我在这里收到错误：

  

MainActivity类型中的方法switchContent（Fragment，String）不适用于参数（ProductListFragment，String）

以下是代码：

package com.example.sp;

import java.util.ArrayList;
import java.util.List;

import android.app.Activity;
import android.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.AdapterView.OnItemLongClickListener;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.Toast;

public class ProductListFragment extends Fragment implements
OnItemClickListener, OnItemLongClickListener{

    public static final String ARG_ITEM_ID = "product_list";

      Activity activity;
      ListView productListView;
      List<Product> products;
      ProductListAdapter productListAdapter;
      SharedPreference sharedPreference;

      @Override
        public void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            activity = getActivity();
            sharedPreference = new SharedPreference();
        }


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

            setProducts();

            productListAdapter = new ProductListAdapter(activity, products);
            productListView.setAdapter(productListAdapter);
            productListView.setOnItemClickListener(this);
            productListView.setOnItemLongClickListener(this);
            return view;
        }

      private void setProducts() {

            Product product1 = new Product(1, "Dell XPS", "Dell XPS Laptop", 60000);
            Product product2 = new Product(2, "HP Pavilion G6-2014TX",
                    "HP Pavilion G6-2014TX Laptop", 50000);
            Product product3 = new Product(3, "ProBook HP 4540",
                    "ProBook HP 4540 Laptop", 45000);
            Product product4 = new Product(4, "HP Envy 4-1025TX",
                    "HP Envy 4-1025TX Laptop", 46000);
            Product product5 = new Product(5, "Dell Inspiron",
                    "Dell Inspiron Laptop", 48000);
            Product product6 = new Product(6, "Dell Vostro", "Dell Vostro Laptop",
                    50000);
            Product product7 = new Product(7, "IdeaPad Z Series",
                    "Lenovo IdeaPad Z Series Laptop", 40000);
            Product product8 = new Product(8, "ThinkPad X Series",
                    "Lenovo ThinkPad X Series Laptop", 38000);
            Product product9 = new Product(9, "VAIO S Series",
                    "Sony VAIO S Series Laptop", 39000);
            Product product10 = new Product(10, "Series 5",
                    "Samsung Series 5 Laptop", 50000);

            products = new ArrayList<Product>();
            products.add(product1);
            products.add(product2);
            products.add(product3);
            products.add(product4);
            products.add(product5);
            products.add(product6);
            products.add(product7);
            products.add(product8);
            products.add(product9);
            products.add(product10);
        }

      private void findViewsById(View view) {
            productListView = (ListView) view.findViewById(R.id.list_product);
        }

    @Override
    public boolean onItemLongClick(AdapterView<?> arg0, View view, int position,
            long arg3) {

         ImageView button = (ImageView) view.findViewById(R.id.imgbtn_favorite);

            String tag = button.getTag().toString();
            if (tag.equalsIgnoreCase("grey")) {
                sharedPreference.addFavorite(activity, products.get(position));
                Toast.makeText(activity,
                        activity.getResources().getString(R.string.add_favr),
                        Toast.LENGTH_SHORT).show();

                button.setTag("red");
                button.setImageResource(R.drawable.heart_red);
            } else {
                sharedPreference.removeFavorite(activity, products.get(position));
                button.setTag("grey");
                button.setImageResource(R.drawable.heart_grey);
                Toast.makeText(activity,
                        activity.getResources().getString(R.string.remove_favr),
                        Toast.LENGTH_SHORT).show();
            }

            return true;
    }

    @Override
    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
         Product product = (Product) parent.getItemAtPosition(position);
            Toast.makeText(activity, product.toString(), Toast.LENGTH_LONG).show();

    }

    @Override
    public void onResume() {
        getActivity().setTitle(R.string.app_name);
        getActivity().getActionBar().setTitle(R.string.app_name);
        super.onResume();
    }

}