Xamarin Android: swipe to delete in the recyclerview its not deleting

Question

Hello everyone my name is Taniguchi

i've created a recyclerview and inserted a swipe on the recyclerview items.

the swipe callback is working i can swipe on recyclerview items, but the code i've made to delete is not working.

When i swipe the line stays red and the item stays on recyclerview.

My notifydatachanged is not rebilding the recyclerview.

my swipe callback

 public class SwipeToDeleteCallback : ItemTouchHelper.SimpleCallback
{
    private View v;
    private List<Email> mEmails;
    private Context context;
    private RecyclerView.Adapter mdapter;
    public static RecyclerView.Adapter mAdapter;
    private Android.Graphics.Drawables.Drawable deleteIcon;
    private int intrinsicWidth;
    private int intrinsicHeight;
    private Android.Graphics.Drawables.ColorDrawable background;
    private Color backgroundColor;
    private Paint clearPaint;

    public SwipeToDeleteCallback(int dragDirs, int swipeDirs, Context context) : base(dragDirs, swipeDirs)
    {
        this.context = context;
        deleteIcon = ContextCompat.GetDrawable(context, Resource.Drawable.alter_delete);
        intrinsicWidth = deleteIcon.IntrinsicWidth;
        intrinsicHeight = deleteIcon.IntrinsicHeight;
        background = new Android.Graphics.Drawables.ColorDrawable();
        backgroundColor = Color.ParseColor("#f44336");
        clearPaint = new Paint();
        clearPaint.SetXfermode(new PorterDuffXfermode(PorterDuff.Mode.Clear));
    }

    public SwipeToDeleteCallback(int dragDirs, int swipeDirs, Context context, RecyclerView.Adapter mRecyclerView) : this(dragDirs, swipeDirs, context)
    {
        this.context = context;
        this.mdapter = mRecyclerView;
        deleteIcon = ContextCompat.GetDrawable(context, Resource.Drawable.alter_delete);
        intrinsicWidth = deleteIcon.IntrinsicWidth;
        intrinsicHeight = deleteIcon.IntrinsicHeight;
        background = new Android.Graphics.Drawables.ColorDrawable();
        backgroundColor = Color.ParseColor("#f44336");
        clearPaint = new Paint();
        clearPaint.SetXfermode(new PorterDuffXfermode(PorterDuff.Mode.Clear));
    }

    public override int GetMovementFlags(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder)
    {
        if (viewHolder.AdapterPosition == 10)
        {
            return 0;
        }
        return base.GetMovementFlags(recyclerView, viewHolder);
    }

    public override void OnChildDraw(Canvas c, RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, float dX, float dY, int actionState, bool isCurrentlyActive)
    {
        base.OnChildDraw(c, recyclerView, viewHolder, dX, dY, actionState, isCurrentlyActive);
    }

    public override bool OnMove(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, RecyclerView.ViewHolder target)
    {
        //throw new NotImplementedException();
        return false;
    }

    public override void OnChildDrawOver(Canvas c, RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, float dX, float dY, int actionState, bool isCurrentlyActive)
    {
        var itemView = viewHolder.ItemView;
        var itemHeight = itemView.Bottom - itemView.Top;
        var isCanceled = dX == 0f && !isCurrentlyActive;

        if (isCanceled)
        {
            clearCanvas(c, itemView.Right + dX, (float)itemView.Top, (float)itemView.Right, (float)itemView.Bottom);
            base.OnChildDrawOver(c, recyclerView
                , viewHolder, dX, dY, actionState, isCurrentlyActive);
            return;
        }
        background.Color = backgroundColor;
        background.SetBounds(itemView.Right + (int)dX, itemView.Top, itemView.Right, itemView.Bottom);
        background.Draw(c);

        var deleteIconTop = itemView.Top + (itemHeight - intrinsicHeight) / 2;
        var deleteIconMargin = (itemHeight - intrinsicHeight) / 2;
        var deleteIconLeft = itemView.Right - deleteIconMargin - intrinsicWidth;
        var deleteIconRight = itemView.Right - deleteIconMargin;
        var deleteIconBottom = deleteIconTop + intrinsicHeight;

        deleteIcon.SetBounds(deleteIconLeft, deleteIconTop, deleteIconRight, deleteIconBottom);
        deleteIcon.Draw(c);

        base.OnChildDrawOver(c, recyclerView, viewHolder, dX, dY, actionState, isCurrentlyActive);
    }

    private void clearCanvas(Canvas c, float v, float top, float right, float bottom)
    {
        c.DrawRect(v, top, right, bottom, clearPaint);
    }

    public override void OnSwiped(RecyclerView.ViewHolder viewHolder, int direction)
    {
        //Invoke Removing Item method from 
        int position = viewHolder.AdapterPosition;
        RecyclerAdapter mAdapter = new RecyclerAdapter(mEmails, this);
        mAdapter.RemoveItem(viewHolder.AdapterPosition);

    }

    public override void ClearView(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder)
    {
        base.ClearView(recyclerView, viewHolder);
    }
}

my recyclerview adapter:

public class RecyclerAdapter : RecyclerView.Adapter
{

    public static RecyclerView.Adapter mAdapter;
    public static bool isActionMode = true;
    public static bool unselect = false;
    private Activity mActivity;
    private List<Email> mEmails;
    private Context context;
    private View p;
    public static bool count = false;
    public static int CountAuxiliar = 0;
    private SwipeToDeleteCallback swipeToDeleteCallback;

    public RecyclerAdapter(List<Email> emails, Context context)
    {
        mEmails = emails;
        this.context = context;
    }

    public RecyclerAdapter(List<Email> emails, Activity activity)
    {
        mEmails = emails;
        mActivity = activity;
    }

    public RecyclerAdapter(List<Email> mEmails, SwipeToDeleteCallback swipeToDeleteCallback)
    {
        this.mEmails = mEmails;
        this.swipeToDeleteCallback = swipeToDeleteCallback;
    }

    public class MyView : RecyclerView.ViewHolder
    {
        public View mMainView { get; set; }
        public TextView mName { get; set; }
        public TextView mSubject { get; set; }
        public TextView mMessage { get; set; }

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

    }

    public override int ItemCount
    {
        get { return mEmails.Count; }
    }

    public override RecyclerView.ViewHolder OnCreateViewHolder(ViewGroup parent, int viewType)
    {
        LayoutInflater inflater = LayoutInflater.From(parent.Context);
        View row = LayoutInflater.From(parent.Context).Inflate(Resource.Layout.row, parent, false);
        RecyclerViewHolder vh = new RecyclerViewHolder(row);
        return vh;
    }
    public override void OnBindViewHolder(RecyclerView.ViewHolder holder, int position)
    {
        RecyclerViewHolder myHolder = holder as RecyclerViewHolder;

        myHolder.mName.Text = mEmails[position].Name;
        myHolder.mSubject.Text = mEmails[position].Subject;
        myHolder.mMessage.Text = mEmails[position].Message;
    }

    public void RemoveItem(int position)
    {
        ArrayList al = new ArrayList(MainActivity.mEmails);
        al.RemoveAt(position);
        NotifyDataSetChanged();
        NotifyItemChanged(position);
    }
}  

where i calling the recylerview and the swipe callback

[Activity(Label = "@string/app_name", Theme = "@style/AppTheme", MainLauncher = true)]
public class MainActivity : AppCompatActivity
{
    public static RecyclerView mRecyclerView;
    public static RecyclerView.LayoutManager mLayoutManager;
    public RecyclerView.ViewHolder holder;
    public static BottomNavigationView bottomnavigationview1;
    public static RecyclerView.Adapter mAdapter;
    public static List<Email> mEmails;


    protected override void OnCreate(Bundle bundle)
    {
        base.OnCreate(bundle);
        Xamarin.Essentials.Platform.Init(this, bundle);
        // Set our view from the "main" layout resource
        SetContentView(Resource.Layout.activity_main);

        mRecyclerView = FindViewById<RecyclerView>(Resource.Id.recyclerViwer);
        mRecyclerView.AddItemDecoration(new DividerItemDecoration(mRecyclerView.Context, DividerItemDecoration.Vertical));
        mRecyclerView.HasFixedSize = true;
        SetupList();

        //Create our layout Manager
        mLayoutManager = new LinearLayoutManager(this);
        mRecyclerView.SetLayoutManager(mLayoutManager);
        RecyclerAdapter mAdapter = new RecyclerAdapter(mEmails, this);
        mRecyclerView.SetAdapter(mAdapter);

        var swipeHandler = new SwipeToDeleteCallback(0, ItemTouchHelper.Left, this, mAdapter);
        var itemTouchHelper = new ItemTouchHelper(swipeHandler);
        itemTouchHelper.AttachToRecyclerView(mRecyclerView);

    }

    private void SetupList()
    {
        for (int i = 1; i <= 2; i++)
        {
            mEmails = new List<Email>();
            mEmails.Add(new Email() { Name = "tom", Subject = "Wanna Hang Out?", Message = "I ' ll   be around  tomorrow!!" });
            mEmails.Add(new Email() { Name = "tom", Subject = "Wanna Hang Out?", Message = "I ' ll   be around  tomorrow!!" });
            mEmails.Add(new Email() { Name = "tom", Subject = "Wanna Hang Out?", Message = "I ' ll   be around  tomorrow!!" });
            mEmails.Add(new Email() { Name = "tom", Subject = "Wanna Hang Out?", Message = "I ' ll   be around  tomorrow!!" });
            mEmails.Add(new Email() { Name = "tom", Subject = "Wanna Hang Out?", Message = "I ' ll   be around  tomorrow!!" });
            mEmails.Add(new Email() { Name = "tom", Subject = "Wanna Hang Out?", Message = "I ' ll   be around  tomorrow!!" });
            mEmails.Add(new Email() { Name = "tom", Subject = "Wanna Hang Out?", Message = "I ' ll   be around  tomorrow!!" });
            mEmails.Add(new Email() { Name = "tom", Subject = "Wanna Hang Out?", Message = "I ' ll   be around  tomorrow!!" });
            mEmails.Add(new Email() { Name = "tom", Subject = "Wanna Hang Out?", Message = "I ' ll   be around  tomorrow!!" });
            mEmails.Add(new Email() { Name = "tom", Subject = "Wanna Hang Out?", Message = "I ' ll   be around  tomorrow!!" });
            mEmails.Add(new Email() { Name = "tom", Subject = "Wanna Hang Out?", Message = "I ' ll   be around  tomorrow!!" });
            mEmails.Add(new Email() { Name = "tom", Subject = "Wanna Hang Out?", Message = "I ' ll   be around  tomorrow!!" });
            mEmails.Add(new Email() { Name = "tom", Subject = "Wanna Hang Out?", Message = "I ' ll   be around  tomorrow!!" });
            mEmails.Add(new Email() { Name = "tom", Subject = "Wanna Hang Out?", Message = "I ' ll   be around  tomorrow!!" });

        }
    }

Answer 1

In the method RemoveItem

public void RemoveItem(int position)
{
  ArrayList al = new ArrayList(MainActivity.mEmails);
  al.RemoveAt(position);
  NotifyDataSetChanged();
  NotifyItemChanged(position);
}

You create a new array al .But you should remove the item from the ItemsSource of Recyclerview .

public void RemoveItem(int position)
{
  mEmails.RemoveAt(position);
  NotifyDataSetChanged();
  NotifyItemChanged(position);
}

Update

Improve your code as follow

in SwipeToDeleteCallback

private RecyclerAdapter mdapter;

public SwipeToDeleteCallback(int dragDirs, int swipeDirs, Context context, RecyclerAdapter mRecyclerView , List<Email> mails) : this(dragDirs, swipeDirs, context)
{
   this.context = context;
   this.mdapter = mRecyclerView;
   deleteIcon = ContextCompat.GetDrawable(context, Resource.Drawable.alter_delete);
   intrinsicWidth = deleteIcon.IntrinsicWidth;
   intrinsicHeight = deleteIcon.IntrinsicHeight;
   background = new Android.Graphics.Drawables.ColorDrawable();
   backgroundColor = Color.ParseColor("#f44336");
   clearPaint = new Paint();
   mEmails = mails;
   clearPaint.SetXfermode(new PorterDuffXfermode(PorterDuff.Mode.Clear));
}

public override void OnSwiped(RecyclerView.ViewHolder viewHolder, int direction)
{
   //Invoke Removing Item method from 
          
   mdapter.RemoveItem(viewHolder.AdapterPosition);

}

in RecyclerAdapter.cs

public void RemoveItem(int position)
{
   mEmails.RemoveAt(position);
   NotifyDataSetChanged();
   NotifyItemChanged(position);
}

in MainActivity

RecyclerAdapter mAdapter = new RecyclerAdapter(mEmails, this);
mRecyclerView.SetAdapter(mAdapter);

var swipeHandler = new SwipeToDeleteCallback(0, ItemTouchHelper.Left, this, mAdapter,mEmails);
var itemTouchHelper = new ItemTouchHelper(swipeHandler);
itemTouchHelper.AttachToRecyclerView(mRecyclerView);