c# - 在添加自己的 LinearLayout 期间无法激活 JNI 句柄 - Xamarin Android

Question

我正在基于 this tutorial 在 Xamarin Android 中创建自己的日历.我将所需的一切从 Java 转换为 C#，但现在当我启动应用程序并打开包含行中自定义日历的 fragment 时:

public override View OnCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        var view = inflater.Inflate(Resource.Layout.calendar_fragment_main, container, false); //System.NotSupportedException Error
        return view;
}

我收到一条错误消息:

System.NotSupportedException - Could not activate JNI Handle 0xffcdb7e8 (key_handle 0x741b240) of Java type 'md57f15d2d0137b5b5d70f719ce3cee21d4/EstiCalendar' as managed type 'EstiMOBILE.Droid.Components.EstiCalendar.Component.Layouts.EstiCalendar'.

还有 2 个其他错误可能来自第一个错误:

Java.Lang.UnsupportedOperationException - Binary XML file line #1: You must supply a layout_width attribute.

Android.Views.InflateException - Binary XML file line #1: Binary XML file line #1: You must supply a layout_width attribute.

包含自定义日历的 fragment (calendar_fragment_main.axml):

    <?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
                xmlns:esticalendar="http://schemas.android.com/apk/res-auto" 
                xmlns:app="http://schemas.android.com/apk/res-auto"
                xmlns:tools="http://schemas.android.com/tools"
                android:orientation="vertical" 
                android:layout_width="match_parent"
                android:layout_height="match_parent">
    <RelativeLayout 
        android:id="@+id/calendar_content_wrapper"
        android:orientation="vertical"
        android:layout_width="match_parent"
        android:layout_height="match_parent">
        <TextView
        android:id="@+id/calendar_title"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        tools:text="Calendar" />
        <CalendarView 
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:layout_below="@id/calendar_title"
        android:id="@+id/calendar_main_object" 
        android:visibility="gone" />
        <EstiMOBILE.Droid.Components.EstiCalendar.Component.Layouts.EstiCalendar
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:id="@+id/esti_calendar"
        esticalendar:date_format="MMMM yyyy" />
    </RelativeLayout>
</RelativeLayout>

我的自定义日历类 EstiCalendar.cs

using System;
using System.Collections.Generic;
using Android.Content;
using Android.Content.Res;
using Android.Graphics;
using Android.Runtime;
using Android.Util;
using Android.Views;
using Android.Widget;
using Java.Text;
using Java.Util;

namespace EstiMOBILE.Droid.Components.EstiCalendar.Component.Layouts
{
    public class EstiCalendar : LinearLayout
    {
        // how many days to show, defaults to six weeks, 42 days
        private static readonly int DAYS_COUNT = 42;

        // default date format
        private static readonly string DATE_FORMAT = "MMM yyyy";

        // date format
        private string dateFormat;

        // current displayed month
        private Calendar currentDate = Calendar.Instance;

        //event handling
        private IEventHandler eventHandler = null;

        // internal components
        private LinearLayout header;
        private ImageView btnPrev;
        private ImageView btnNext;
        private TextView txtDate;
        private GridView grid;

        // seasons' rainbow
        int[] rainbow = new int[] {
            Resource.Color.summer,
            Resource.Color.fall,
            Resource.Color.winter,
            Resource.Color.spring
    };

        // month-season association (northern hemisphere, sorry australia :)
        readonly int[] monthSeason = { 2, 2, 3, 3, 3, 0, 0, 0, 1, 1, 1, 2 };

        public EstiCalendar(IntPtr handle, JniHandleOwnership transfer) : base(handle, transfer)
        {
        }

        public EstiCalendar(Context context, IAttributeSet attrs) : base(context, attrs)
        {
            InitControl(context, attrs);
        }

        public EstiCalendar(Context context, IAttributeSet attrs, int defStyleAttr) : base(context, attrs, defStyleAttr)
        {
            InitControl(context, attrs);
        }

        /**
         * Load control xml layout
         */
        private void InitControl(Context context, IAttributeSet attrs)
        {
            LayoutInflater inflater = (LayoutInflater)context.GetSystemService(Context.LayoutInflaterService);
            inflater.Inflate(Resource.Layout.calendar_control, this);

            LoadDateFormat(attrs);
            AssignUiElements();
            AssignClickHandlers();

            UpdateCalendar();
        }

        private void LoadDateFormat(IAttributeSet attrs)
        {
            TypedArray ta = Context.ObtainStyledAttributes(attrs, Resource.Styleable.EstiCalendar);

            try
            {
                // try to load provided date format, and fallback to default otherwise
                dateFormat = ta.GetString(Resource.Styleable.EstiCalendar_date_format);
                if (dateFormat == null)
                    dateFormat = DATE_FORMAT;
            }
            finally
            {
                ta.Recycle();
            }
        }
        private void AssignUiElements()
        {
            // layout is inflated, assign local variables to components
            header = (LinearLayout)FindViewById(Resource.Id.calendar_header);
            btnPrev = (ImageView)FindViewById(Resource.Id.calendar_prev_button);
            btnNext = (ImageView)FindViewById(Resource.Id.calendar_next_button);
            txtDate = (TextView)FindViewById(Resource.Id.calendar_date_display);
            grid = (GridView)FindViewById(Resource.Id.calendar_grid);
        }

        private void AssignClickHandlers()
        {
            btnNext.Click += (sender, e) =>
            {
                currentDate.Add(Calendar.Month, 1);
                UpdateCalendar();
            };

            btnPrev.Click += (sender, e) =>
            {
                currentDate.Add(Calendar.Month, -1);
                UpdateCalendar();
            };

            grid.ItemLongClick += (object sender, AdapterView.ItemLongClickEventArgs e) => {
                if (eventHandler != null)
                {
                    eventHandler.OnDayLongPress((Date)e.Position);
                }
            };

        }

        public void UpdateCalendar()
        {
            UpdateCalendar(null);
        }

        /**
         * Display dates correctly in grid
         */
        public void UpdateCalendar(HashSet<Date> events)
        {
            List<Date> cells = new List<Date>();
            Calendar calendar = (Calendar)currentDate.Clone();

            // determine the cell for current month's beginning
            calendar.Set(Calendar.DayOfMonth, 1);
            int monthBeginningCell = calendar.Get(Calendar.DayOfWeek) - 1;

            // move calendar backwards to the beginning of the week
            calendar.Add(Calendar.DayOfMonth, -monthBeginningCell);

            // fill cells
            while (cells.Count < DAYS_COUNT)
            {
                cells.Add(calendar.Time);
                calendar.Add(Calendar.DayOfMonth, 1);
            }

            // update grid
            grid.Adapter = new CalendarAdapter(Context, cells, events);

            // update title
            SimpleDateFormat sdf = new SimpleDateFormat(dateFormat);
            txtDate.Text = sdf.Format(currentDate.Time);

            // set header color according to current season
            int month = currentDate.Get(Calendar.Month);
            int season = monthSeason[month];
            int color = rainbow[season];

            header.SetBackgroundColor(Resources.GetColor(color));
        }


        private class CalendarAdapter : BaseAdapter<Date>
        {
            // days with events
            private HashSet<Date> eventDays;

            private List<Date> days;

            // for view inflation
            private LayoutInflater inflater;

            private Context context;

            public CalendarAdapter(Context context, List<Date> days, HashSet<Date> eventDays) : base()
            {
                this.eventDays = eventDays;
                this.days = days;
                inflater = LayoutInflater.From(context);
                this.context = context;
            }

            public override Date this[int position] => days[position];

            public override int Count => days.Count;

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

            public override View GetView(int position, View convertView, ViewGroup parent)
            {
                // day in question
                var date = GetItem(position) as Date;
                int day = date.GetDate();
                int month = date.Month;
                int year = date.Year;

                // today
                Date today = new Date();

                // inflate item if it does not exist yet
                if (convertView == null)
                    convertView = inflater.Inflate(Resource.Layout.control_calendar_day, parent, false);

                // if this day has an event, specify event image
                convertView.SetBackgroundResource(0);
                if (eventDays != null)
                {
                    foreach (Date eventDate in eventDays)
                    {
                        if (eventDate.GetDate() == day &&
                                eventDate.Month == month &&
                                eventDate.Year == year)
                        {
                            // mark this day for event
                            convertView.SetBackgroundResource(Resource.Drawable.reminder);
                            break;
                        }
                    }
                }

                // clear styling
                ((TextView)convertView).SetTypeface(null, TypefaceStyle.Normal);
                ((TextView)convertView).SetTextColor(Color.Black);

                if (month != today.Month || year != today.Year)
                {
                    // if this day is outside current month, grey it out
                    ((TextView)convertView).SetTextColor(context.Resources.GetColor(Resource.Color.greyed_out));
                }
                else if (day == today.GetDate())
                {
                    // if it is today, set it to blue/bold
                    ((TextView)convertView).SetTypeface(null, TypefaceStyle.Bold);
                    ((TextView)convertView).SetTextColor(context.Resources.GetColor(Resource.Color.today));
                }

                // set text
                ((TextView)convertView).Text = $"{date.GetDate()}";

                return convertView;
            }
        }


        public void SetEventHandler(IEventHandler eventHandler)
        {
            this.eventHandler = eventHandler;
        }


        public interface IEventHandler
        {
            void OnDayLongPress(Date date);
        }
    }
}

CalendarFragment.cs 包含错误:

using System;
using System.Collections.Generic;
using Android.OS;
using Android.Runtime;
using Android.Views;
using Android.Widget;
using EstiMOBILE.Droid.Components.EstiCalendar.Component.Layouts;
using EstiMOBILE.Droid.Fragments.BaseFragments;
using Java.Util;

namespace EstiMOBILE.Droid.Fragments.CustomFragments
{
    public class CalendarFragment : BaseFragment
    {
        public override void OnCreate(Bundle savedInstanceState)
        {
            base.OnCreate(savedInstanceState);
        }

        public static CalendarFragment NewInstance()
        {
            var frag1 = new CalendarFragment { Arguments = new Bundle() };
            return frag1;
        }

        public override View OnCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
        {
            var view = inflater.Inflate(Resource.Layout.calendar_fragment_main, container, false); //Error

            //InitCustomCalendar(view);
            return view;
        }

        public void InitCustomCalendar(View view)
        {
            HashSet<Date> events = new HashSet<Date>
            {
                new Date()
            };

            EstiCalendar cv = (EstiCalendar) view.FindViewById(Resource.Id.esti_calendar);
            cv.UpdateCalendar(events);

        }
    }
}

你有什么帮助，我怎样才能摆脱这个错误？

Answer 1

使用IntPtr 和JniHandleOwnership 添加构造函数

public EstiCalendar(IntPtr handle, JniHandleOwnership transfer) : base(handle, transfer)
{
}

这就是 Java 获取 Android 可调用包装器 (ACW) 的方式。所以这个 ctor 将在任何其他 ctors 之前被击中。