自定义 ListView 中的 BaseAdapter，如何使其在空视图中更加健壮

问题描述

我有这段代码通常可以正常工作，但在某些装有 Android 9 的设备中，只有我收到此异常：

HistoryListViewAdapter+<>c__displayClass8_0.<GetView>b__0 ()
java.lang.NullPointerException: Attempt to invoke virtual method 'int java.lang.String.length()' on a null object reference

jnienvironment+Staticmethods.CallStaticObjectMethod (Java.Interop.JniObjectReference type,Java.Interop.JniMethodInfo method,Java.Interop.JniArgumentValue* args)
JniPeerMembers+JniStaticmethods.InvokeObjectMethod (System.String encodedMember,Java.Interop.JniArgumentValue* parameters)
HtmlCompat.FromHtml (System.String source,system.int32 flags)
HistoryListViewAdapter+<>c__displayClass8_0.<GetView>b__0 ()
MainThread.BeginInvokeOnMainThread (System.Action action)
HistoryListViewAdapter.GetView (system.int32 position,Android.Views.View convertView,Android.Views.ViewGroup parent)
BaseAdapter.n_GetView_ILandroid_view_View_Landroid_view_ViewGroup_ (system.intPtr jnienv,system.intPtr native__this,system.int32 position,system.intPtr native_convertView,system.intPtr native_parent)
androidx.core.text.HtmlCompat.fromHtml HtmlCompat.java:148
crc64441aa66e1467637c.HistoryListViewAdapter.n_getView(Native Method)
crc64441aa66e1467637c.HistoryListViewAdapter.getView HistoryListViewAdapter.java:56
android.widget.AbsListView.obtainView AbsListView.java:2375
androidx.viewpager.widget.ViewPager.onLayout ViewPager.java:1775
android.view.View.layout View.java:20871
androidx.coordinatorlayout.widget.CoordinatorLayout.onLayout CoordinatorLayout.java:918
android.view.View.layout View.java:20871
androidx.drawerlayout.widget.DrawerLayout.onLayout DrawerLayout.java:1263
android.view.View.layout View.java:20871

我猜测问题出在我的适配器上，需要改进以更有效地处理所有情况，但我不确定如何改进我的代码，这是我的适配器代码：

using Android.App;
using Android.Views;
using Android.Widget;
using AndroidX.Core.Text;
using System.Collections.Generic;
using Xamarin.Essentials;

namespace KinoStats
{
    public class HistoryListViewAdapter : BaseAdapter<string>
    {
        private readonly Activity Activity;
        private readonly List<string> Data;

        public HistoryListViewAdapter(Activity Activity,List<string> Data) : base()
        {
            this.Activity = Activity;
            this.Data = Data;
        }

        public override string this[int position] => Data[position];

        public override int Count => Data.Count;

        public override long GetItemId(int position)
        {
            return position;
        }

        public override View GetView(int position,View convertView,ViewGroup parent)
        {
            if (convertView == null)
                convertView = Activity.LayoutInflater.Inflate(Resource.Layout.SingleHistoryListViewItem,null);

            var historyItemTextView = convertView.FindViewById<TextView>(Resource.Id.HistoryItemTextView);

            MainThread.BeginInvokeOnMainThread(() =>
            {
                historyItemTextView.SetText(
                HtmlCompat.FromHtml(Data[position],HtmlCompat.FromHtmlModeLegacy),TextView.BufferType.Spannable);
            });

            return convertView;
        }
    }
}

解决方法

暂无找到可以解决该程序问题的有效方法，小编努力寻找整理中！

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