如何在使用抽屜切換ListFragment時保存ArrayList中的更改ListView

Question

我有一個帶有項目水果，蔬菜，肉類的抽屜列表視圖。每個類都有一個擴展ListFragment的類。我還爲我的ArrayList和ArrayAdapter創建了一個Product類。但每次我切換ListFragment和切換回來，我所做的更改也重置，而不是保存。

這裏是我當前的代碼：

product_adapter.java

//imports .... 

public class product_adapter extends ArrayAdapter<product> { 

    public product_adapter(Context context, ArrayList<product> prod) { 
     super(context, 0, prod); 
    } 
    @Override 
    public View getView(int position, View convertView, ViewGroup parent) { 

     final product products = getItem(position); 

     // Some Codes for Instantiation and LayoutInflater 


     itemAdd.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View view) { 
       products.itemQuantity ++; 
       viewHolder.itemQuantity.setText(String.valueOf(products.getItemQuantity())); 
       notifyDataSetChanged(); 
      } 
     }); 
     return convertView; 
    } 
} 

Fruit.java

public class Fruit extends ListFragment { 

    public ArrayList<product> products; 
    public product_adapter productAdapter; 

    @Override 
    public void onActivityCreated(@Nullable Bundle savedInstanceState) { 
     super.onActivityCreated(savedInstanceState); 

     products = new ArrayList<product>(); 

     products.add(new product("Apple", 18.00 /*Price*/, 0 /*Quantity*/)); 
     products.add(new product("Orange", 16.00 /*Price*/, 0 /*Quantity*/)); 

     productAdapter = new product_adapter(getActivity(),products); 

     setListAdapter(productAdapter); 
    } 
} 

蔬菜和肉類的構造方式爲水果類相同

與ListView的MainActivity

//Some codes here for the creating ListView 
     listView = (ListView) findViewById(R.id.categoryView); 
     listView.setAdapter(new category_adapter(this, categories)); 
     drawerLayout = (DrawerLayout) findViewById(R.id.drawerView); 

     listView.setOnItemClickListener(new AdapterView.OnItemClickListener() { 
      @Override 
      public void onItemClick(AdapterView<?> adapterView, View view, int position, long l) { 
       ListFragment listFragment = null; 
       switch (position){ 
        case 0: 
         listFragment = new Fruit(); 
         break; 
        case 1: 
         listFragment = new Veggies(); 
         break; 
        case 2: 
         listFragment = new Meat(); 
         break; 
       } 

       FragmentManager fragmentManager = getSupportFragmentManager(); 
       fragmentManager.beginTransaction().replace(R.id.itemLayout,listFragment).commit(); 
       drawerLayout.closeDrawers(); 
      } 
     }); 

Answer 1

@ mark.jon下面是我要生產分類使用擴展列表上抽屜列表實現代碼..希望這會滿足您的需求.. Default Navigation Drawer View to ExpandableListView