滚动时显示空白的Cardview

Question

I have problem with Cardview inside RecyclerView. Card contains ImageView and Textbox. At the beggining all cards are on the screen, but after scrolling down and scrolling up on the screen between are empty spaces.

cardview layout

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:cardview="http://schemas.android.com/apk/res-auto"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:gravity="center_horizontal">
    <android.support.v7.widget.CardView
        android:layout_width="fill_parent"
        android:layout_height="245dp"
        android:layout_gravity="center_horizontal"
        android:id="@+id/eventCardView"
        cardview:cardCornerRadius="5dp">
        <RelativeLayout
            android:layout_width="fill_parent"
            android:layout_height="fill_parent"
            android:orientation="vertical">
            <ImageView
                android:layout_width="fill_parent"
                android:layout_height="240dp"
                android:layout_alignParentLeft="true"
                android:layout_alignParentTop="true"
                android:id="@+id/eventImage"
                android:scaleType="centerCrop" />
        </RelativeLayout>
    </android.support.v7.widget.CardView>
</LinearLayout>

Adapter

using System.Collections.Generic;
using Android.Content;
using Android.Content.Res;
using Android.Support.V7.Widget;
using Android.Views;
using Android.Widget;
using EVENTS_MOBILE.Activities;
using EVENTS_MOBILE.CORE.Models;
using EVENTS_MOBILE.Utilities;

namespace EVENTS_MOBILE.Adapters
{
    public class RecyclerAdapter : RecyclerView.Adapter
    {
        private readonly List<SimplestEventModel> _events;
        private readonly RecyclerView _recyclerView;
        private readonly Context _context;
        public RecyclerAdapter(List<SimplestEventModel> events, RecyclerView recyclerView, Context context)
        {
            _context = context;
            _events = events;
            _recyclerView = recyclerView;
        }
        public override void OnBindViewHolder(RecyclerView.ViewHolder holder, int position)
        {
            if (holder is MyView myHolder)
            {
                //myHolder.Name.Text = _events[position].Name;

                //myHolder.Image.SetImageBitmap(ImageHelper.GetImageBitmapFromUrl(_events[position].ImageLink)); 
                myHolder.Image.SetImageResource((int)typeof(Resource.Drawable).GetField("test_image").GetValue(null));

            if (!myHolder.Image.HasOnClickListeners)
            {
                myHolder.Image.Click += delegate
                {
                    var intent = new Intent(_context, typeof(SingleEventActivity));
                    intent.PutExtra("eventId", position);
                    _context.StartActivity(intent);
                };
            }
            }
        }

        public override RecyclerView.ViewHolder OnCreateViewHolder(ViewGroup parent, int viewType)
        {
            View row = LayoutInflater.From(parent.Context).Inflate(Resource.Layout.card_layout, parent, false);

            //TextView txtName = row.FindViewById<TextView>(Resource.Id.eventTitle);
            ImageView image = row.FindViewById<ImageView>(Resource.Id.eventImage);

            MyView view = new MyView(row)
            {
                //Name = txtName,
                Image = image
            };
            return view;
        }

        public override int ItemCount => _events.Count;

        public class MyView : RecyclerView.ViewHolder
        {
            public View MainView { get; set; }
            //public TextView Name { get; set; }
            public ImageView Image { get; set; }

            public MyView(View view) : base(view)
            {
                MainView = view;
            }
        }

    }
}

EventsFragment

using System;
using Android.OS;
using Android.Views;
using EVENTS_MOBILE.Adapters;
using EVENTS_MOBILE.CORE.Models;
using System.Collections.Generic;
using System.Threading;
using System.Threading.Tasks;
using Android.App;
using Android.Support.V7.Widget;
using Android.Widget;
using EVENTS_MOBILE.CORE.Services;

namespace EVENTS_MOBILE.Fragments
{
    public class EventsFragment : Fragment
    {
        protected EventsService EventsService;
        protected List<SimplestEventModel> Events = new List<SimplestEventModel>();
        protected RecyclerView _recyclerView;
        protected RecyclerView.LayoutManager LayoutManager;
        protected RecyclerView.Adapter Adapter;
        private ProgressBar _progressBar;


        public override void OnCreate(Bundle savedInstanceState)
        {
            base.OnCreate(savedInstanceState);
        }

        private void LoadAllEvents(string category)
        {
            EventsService = new EventsService(category);
        }
        public override void OnActivityCreated(Bundle savedInstanceState)
        {
            base.OnActivityCreated(savedInstanceState);
            FindViews();

            //Events = EventsService.GetAllEventsForCategory();

            Adapter = new RecyclerAdapter(MockSimpleEvents(), _recyclerView, this.Context);
            _recyclerView.SetAdapter(Adapter);

        }

        public override View OnCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
        {
            return inflater.Inflate(Resource.Layout.eventsFragment, container, false);
        }

        protected void FindViews()
        {
            _recyclerView = this.View.FindViewById<RecyclerView>(Resource.Id.recyclerView);
            _progressBar = this.View.FindViewById<ProgressBar>(Resource.Id.progressbar_view);

            LayoutManager = new LinearLayoutManager(this.Context);
            _recyclerView.SetLayoutManager(LayoutManager);
        }
}

EventsActivity

using System;
using Android.App;
using Android.OS;
using Android.Support.Design.Widget;
using Android.Support.V7.App;
using Android.Views;
using Android.Widget;
using EVENTS_MOBILE.Fragments;

namespace EVENTS_MOBILE.Activities
{
    [Activity(Label="EVENTS",Theme = "@style/Theme.AppCompat.Light.DarkActionBar")]
    public class EventsActivity : Activity
    {
        public string Email = String.Empty;
        public string Category = String.Empty;
        BottomNavigationView _bottomNavigation;
        protected override void OnCreate(Bundle savedInstanceState)
        {
            try
            {
                base.OnCreate(savedInstanceState);
                Email = Intent.GetStringExtra("email");
                Category = Intent.GetStringExtra("category");
                SetContentView(Resource.Layout.menu);

                _bottomNavigation = FindViewById<BottomNavigationView>(Resource.Id.bottom_navigation);
                _bottomNavigation.NavigationItemSelected += BottomNavigation_NavigationItemSelected;

                LoadFragment(Resource.Id.events);
            }
            catch (Exception e)
            {
                Console.WriteLine(e.Message);
                Console.WriteLine(e.StackTrace);
            }
        }

        private void BottomNavigation_NavigationItemSelected(object sender, BottomNavigationView.NavigationItemSelectedEventArgs e)
        {
            LoadFragment(e.Item.ItemId);
        }
        private void LoadFragment(int id)
        {
            FragmentTransaction fragmentTx = this.FragmentManager.BeginTransaction();

            switch (id)
            {
                case Resource.Id.events:
                    EventsFragment eventsFragment = new EventsFragment();
                    fragmentTx.Replace(Resource.Id.fragmentContainer, eventsFragment);
                    fragmentTx.AddToBackStack(null);
                    fragmentTx.Commit();
                    break;
                case Resource.Id.map:
                    var nearestEventsFragment = new NearestEventsFragment();
                    fragmentTx.Replace(Resource.Id.fragmentContainer, nearestEventsFragment);
                    fragmentTx.AddToBackStack(null);
                    fragmentTx.Commit();
                    break;
                case Resource.Id.observed:
                    WatchListFragment watchlistfragment = new WatchListFragment(Email);
                    fragmentTx.Replace(Resource.Id.fragmentContainer, watchlistfragment);
                    Bundle args = new Bundle();
                    args.PutString("Email", Email);
                    watchlistfragment.Arguments = args;
                    fragmentTx.AddToBackStack(null);
                    fragmentTx.Commit();
                    break;
            }
        }
    }
}

menu.axml (container for fragments)

<RelativeLayout
  xmlns:android="http://schemas.android.com/apk/res/android"
  xmlns:app="http://schemas.android.com/apk/res-auto"
  android:orientation="vertical"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  android:background="@drawable/gradient">
  <FrameLayout
    android:id="@+id/fragmentContainer"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />
  <android.support.design.widget.BottomNavigationView
    android:id="@+id/bottom_navigation"
    android:layout_width="match_parent"
    android:layout_height="70dp"
    android:layout_gravity="start"
    android:layout_alignParentBottom="true"
    app:elevation="16dp"
    android:background="@drawable/gradient"
    app:itemIconTint="@drawable/nav_item_color"
    app:itemTextColor="@drawable/nav_item_color"
    app:menu="@menu/bottom_navigation_bar" />
</RelativeLayout>

eventsFragment.axml layout for this view

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <android.support.v7.widget.RecyclerView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/recyclerView" />
</LinearLayout>

At the beginning everything is Okay: https://i.stack.imgur.com/9j7Pp.png

But after scrolling it looks like that: https://i.stack.imgur.com/gG6q5.png

Does anybody know something about this strange behavior?

Answer 1

The root LinearLayout in your card view xml uses fill_parent for both width and height:

 android:layout_width="fill_parent" android:layout_height="fill_parent" 

Change the height to wrap_content and this should solve the problem.