我开发了一个自定义适配器，它从 SQLite 获取数据。数据正在选择，适配器也正在获取数据。但它没有显示在 ListView 中。我没有收到任何错误。我在适配器中打印了数据，但只显示了一组数据。并非所有数据。

我已经开发并遵循了正常的自定义适配器实现示例。

我有些疑惑。

1-在我的 customAdapter 类中。当我在调用 findviewById() 时为适配器中的自定义行膨胀 XML 时，只有一个 TextView 显示“它可能产生空指针异常”。为什么？我的 ListView 行的 xml。

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
                android:orientation="vertical"
                android:paddingTop="4dip"
                android:paddingBottom="6dip"
                android:paddingLeft="10dip"
                android:paddingRight="10dip"
                android:layout_width="fill_parent"
                android:layout_height="fill_parent"
                android:weightSum="1">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/row_item_name"
        android:textColor="@color/item_name_color"
        android:layout_alignParentLeft="true"
        />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/row_item_price"

        android:textColor="@color/item_price_color"
        android:layout_alignParentTop="true"
        android:layout_alignParentRight="true"
        android:layout_alignParentEnd="true" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/row_item_contains"

        android:layout_gravity="left"
        android:layout_below="@id/row_item_name"
        android:layout_toRightOf="@id/row_item_name" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"

        android:id="@+id/row_item_quantity"
        android:layout_above="@id/row_item_contains"
        android:paddingRight="10dip"
        android:layout_toLeftOf="@id/row_item_price" />


</RelativeLayout>

1. 在我的 fragment 类中，上面还显示了膨胀 ListView 元素的警告。 下面给出了我的 fragment xml。

   <TextView
       android:id="@+id/tableTextview"
       android:layout_width="wrap_content"
       android:layout_height="wrap_content"
       android:layout_gravity="left"
       android:text="@string/table"
       android:layout_alignParentTop="true"
       android:layout_alignParentLeft="true"
       android:layout_alignParentStart="true" />
   
   <TextView
       android:id="@+id/userName"
       android:layout_width="wrap_content"
       android:layout_height="wrap_content"
       android:layout_alignParentEnd="true"
       android:layout_alignParentRight="true"
       android:layout_gravity="right"
       android:textColor="@color/bg" />
   
   
   
   <EditText
       android:paddingTop="6dp"
       android:id="@+id/tableNumber"
       android:layout_width="wrap_content"
       android:layout_height="wrap_content"
       android:inputType="number"
       android:maxWidth="@dimen/tableNoSize"
       android:layout_below="@id/tableTextview"
       android:layout_alignRight="@id/tableTextview"
       android:layout_alignEnd="@id/tableTextview" />
   
   <TextView
       android:id="@+id/textView"
       android:layout_width="wrap_content"
       android:layout_height="wrap_content"
       android:layout_alignLeft="@id/tableNumber"
       android:layout_alignStart="@id/tableNumber"
       android:layout_below="@id/tableNumber"
       android:layout_gravity="center"
       android:paddingTop="6dip"
       android:paddingBottom="4dip"
       android:text="@string/Menu" />
   
   <ListView
       android:layout_below="@id/textView"
       android:id="@+id/bearer_menu_order_list"
       android:layout_width="wrap_content"
       android:layout_height="0dp">
   </ListView>
   
   <Button
       android:id="@+id/placeButton"
       android:layout_width="wrap_content"
       android:layout_height="wrap_content"
       android:layout_below="@id/textView"
       android:layout_gravity="center_horizontal"
       android:background="@color/buttonColor"
       android:text="@string/placeOrder" />
   

我的适配器代码

    public class MenuListAdapter extends BaseAdapter {
    private List<MenuData> list;
    private Context context;

    public MenuListAdapter(Context context, List<MenuData> list) {
        this.context = context;
        this.list = list;
        Log.e("Hee",list.size()+"");
    }
    @Override
    public int getCount() {
        return list.size();
    }

    @Override
    public Object getItem(int position) {
        return list.get(position);
    }

    @Override
    public long getItemId(int position) {
        return position;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {

        //Log.e("list got--",""+list.size());
        Log.e("position ",""+position);

        ViewHolder holder;
        LayoutInflater inflater =(LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);

        if (convertView == null){
            convertView = inflater.inflate(R.layout.row_list_create_new,null);
            holder = new ViewHolder();
            try{
                holder.txtName=(TextView)convertView.findViewById(R.id.row_item_name);
                holder.txtContains=(TextView)convertView.findViewById(R.id.row_item_contains);
                holder.txtPrice=(TextView)convertView.findViewById(R.id.row_item_price);
                holder.txtQuantity=(TextView)convertView.findViewById(R.id.row_item_quantity);
                convertView.setTag(holder);
                Log.e("covertView-","Null");
            }
            catch (NullPointerException e){
                e.printStackTrace();
            }

        }
        else {
            Log.e("covertView-","Not Null");
            holder = (ViewHolder) convertView.getTag();
        }

        MenuData currentRow=list.get(position);
        Log.e("item ",currentRow.getKEY_ITEM_NAME());
        holder.txtName.setText(currentRow.getKEY_ITEM_NAME());
        holder.txtContains.setText(currentRow.getKEY_ITEM_CONTENTS());
        holder.txtPrice.setText(currentRow.getKEY_PRICE());

        return convertView;
    }


    class ViewHolder {
        public TextView txtName;
        public TextView txtPrice;
        public TextView txtContains;
        public TextView txtQuantity;

    }

}

fragment 代码为

 public class CreateOrderFragment extends Fragment {

    List<MenuData> listMenu;
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View rootView;
        listMenu=new ArrayList<MenuData>();
        rootView = inflater.inflate(R.layout.fragment_create_new_order_list_sections, container, false);
        Context context=getActivity();
        //View view=getView();
        ListView menuList;
        menuList=(ListView) rootView.findViewById(R.id.bearer_menu_order_list);
        menuList.setVisibility(View.VISIBLE);
        DatabaseHelper helper=new DatabaseHelper(context);
        listMenu = helper.getMenuItem();
        Log.e("list menu--",listMenu.size()+"");
        MenuListAdapter adapter=new MenuListAdapter(context,listMenu);
        Log.e("list adapter--",""+adapter.getCount());
        menuList.setAdapter(adapter);
        menuList.setVisibility(View.VISIBLE);

        return rootView;
    }



    @Override
    public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        String user;
        TextView tv;
}
}

最佳答案

试试这个方法:

 ListView menuList;
 public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    View rootView;
    rootView = inflater.inflate(R.layout.fragment_create_new_order_list_sections, container, false);

    menuList=(ListView) rootView.findViewById(R.id.bearer_menu_order_list);
    DatabaseHelper helper=new DatabaseHelper(getActivity());
    listMenu = helper.getMenuItem();
    Log.e("list menu--",listMenu.size()+"");
    MenuListAdapter adapter=new MenuListAdapter(getActivity(),listMenu);
    Log.e("list adapter--",""+adapter.getCount());
    menuList.setAdapter(adapter);
    menuList.setVisibility(View.VISIBLE);

    return rootView;
}

并从 onActivityCreated(....) 中删除所有代码并给我反馈。

关于android - 自定义适配器不显示数据，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/22317195/