Question

我在Android应用程序中使用expandablelistadapter。实际上根据我的要求，我正在显示一个组标题，该组的每个孩子都包含3个文本视图。但是我无法运行我的应用程序，因为我在GetChild，GetChildView和GetGroup，GetGroupView附近遇到错误。

错误信息如下（我粗体提到）

我尝试显式转换类型，但它不起作用。在这方面请帮助我，因为我的工作因此而被推迟。

public override Java.Lang.Object GetGroup(int groupPosition)
        {
            return groups[groupPosition]; - > Cannot implicitly convert type DiningGroup to Java.Lang.Object

        } 

public override Java.Lang.Object GetChild(int groupPosition, int childPosition)
        {
            List<DiningChild> chList = groups[groupPosition].Items;
            return chList[childPosition];  - > Cannot implicitly convert type DiningChild to Java.Lang.Object


        }

  public override View GetChildView(int groupPosition, int childPosition,
                bool isLastChild, View convertView, ViewGroup parent)
        {

            DiningChild child = (DiningChild)GetChild(groupPosition, childPosition);  - > cannot convert type Java.lang.Object to DiningChild



            if (convertView == null)
            {

                convertView = _activity.LayoutInflater.Inflate(Resource.Layout.Dining_ListControl_ChildItem, null);


            }
            var tvfooditem = convertView.FindViewById<TextView>(Resource.Id.txtfooditem);
            var tvfooddesc = convertView.FindViewById<TextView>(Resource.Id.txtfooddesc);
            var tvfoodprice = convertView.FindViewById<TextView>(Resource.Id.txtfoodprice);


            tvfooditem.SetText(child.FoodItemName, TextView.BufferType.Normal);
            tvfooddesc.SetText(child.FoodDescription, TextView.BufferType.Normal);
            tvfoodprice.SetText(child.FoodPrice, TextView.BufferType.Normal);



            return convertView;
        }

      public override View GetGroupView(int groupPosition, bool isExpanded,
                View convertView, ViewGroup parent)
        {
            DiningGroup group = (DiningGroup)GetGroup(groupPosition); - > cannot convert type Java.lang.Object to DiningGroup
            if (convertView == null)
            {
                convertView = _activity.LayoutInflater.Inflate(Resource.Layout.Dining_ListControl_Group, null);
            }


            var tvcategoryname = convertView.FindViewById<TextView>(Resource.Id.txtCategory);

            tvcategoryname.SetText(group.Name, TextView.BufferType.Normal);


            return convertView;




        }

Answer 1

如注释中所述，对于返回Java.Lang.Object的方法，抛出NotImplementedException。添加您自己的方法以使用指定的参数获取DiningChild。

public override Java.Lang.Object GetGroup(int groupPosition)
{
    throw new NotImplementedException();
} 

public override Java.Lang.Object GetChild(int groupPosition, int childPosition)
{
    throw new NotImplementedException();
}

protected GetDiningChild GetDiningChild(int groupPosition, int childPosition)
{
    List<DiningChild> chList = groups[groupPosition].Items;
    return chList[childPosition];
}

protected GetDiningGroup GetDiningGroup(int groupPosition)
{
    return groups[groupPosition];
}

public override View GetChildView(int groupPosition, int childPosition, bool isLastChild, View convertView, ViewGroup parent)
{

    DiningChild child = GetDiningChild(groupPosition, childPosition);
    if (convertView == null)
    {

        convertView = _activity.LayoutInflater.Inflate(Resource.Layout.Dining_ListControl_ChildItem, null);
    }

    var tvfooditem = convertView.FindViewById<TextView>(Resource.Id.txtfooditem);
    var tvfooddesc = convertView.FindViewById<TextView>(Resource.Id.txtfooddesc);
    var tvfoodprice = convertView.FindViewById<TextView>(Resource.Id.txtfoodprice);

    tvfooditem.SetText(child.FoodItemName, TextView.BufferType.Normal);
    tvfooddesc.SetText(child.FoodDescription, TextView.BufferType.Normal);
    tvfoodprice.SetText(child.FoodPrice, TextView.BufferType.Normal);

    return convertView;
}

public override View GetGroupView(int groupPosition, bool isExpanded, View convertView, ViewGroup parent)
{
    DiningGroup group = GetDiningGroup(groupPosition); 
    if (convertView == null)
    {
        convertView = _activity.LayoutInflater.Inflate(Resource.Layout.Dining_ListControl_Group, null);
    }

    var tvcategoryname = convertView.FindViewById<TextView>(Resource.Id.txtCategory);

    tvcategoryname.SetText(group.Name, TextView.BufferType.Normal);

    return convertView;
}

无法在xamarin android listadapter类中隐式转换类型类为java.lang.object

1 个答案: