How to delete row in ReCyclerListView On Click of Menu button in Contextual Action Bar In Xamarin Android?

问题

I have followed below link on how to implement Contextual action bar with Recycler View https://stackoverflow.com/a/45911314/6117355...Can any one tell me how to perform some action like (edit/delete) operations on rows of Recyclerview on based of button actions of Contextual action bar in xamarin Android?

回答1:

Can any one tell me how to perform some action like (edit/delete) operations on rows of Recyclerview on based of button actions of Contextual action bar in xamarin Android?

Firstly, you need to modify PhotoAlbum.cs's Photo[] to a List<Photo> to let it support delete/update operation:

public class PhotoAlbum
{
    // Built-in photo collection - this could be replaced with
    // a photo database:

    ...

    // Array of photos that make up the album:
    private List<Photo> mPhotos;

    // Random number generator for shuffling the photos:
    Random mRandom;

    // Create an instance copy of the built-in photo list and
    // create the random number generator:
    public PhotoAlbum ()
    {
        mPhotos =new List<Photo>( mBuiltInPhotos);
        mRandom = new Random();
    }

    // Return the number of photos in the photo album:
    public int NumPhotos 
    { 
        get { return mPhotos.Count; } 
    }

    // Indexer (read only) for accessing a photo:
    public Photo this[int i] 
    {
        get { return mPhotos[i]; }
    }
    // Add this Method to support update operation
    public void UpdateAt(int position, Photo photo)
    {
        if (photo != null)
            mPhotos[position] = photo;
    }

    public Photo GetAt(int position)
    {
        return mPhotos[position];
    }
    // Add this Method to support delete operation
    public void RemoveAt(int position)
    {
        mPhotos.RemoveAt(position);
    }

    // Pick a random photo and swap it with the top:
    public int RandomSwap()
    {
        // Save the photo at the top:
        Photo tmpPhoto = mPhotos[0];

        // Generate a next random index between 1 and 
        // Length (noninclusive):
        int rnd = mRandom.Next(1, mPhotos.Count);

        // Exchange top photo with randomly-chosen photo:
        mPhotos[0] = mPhotos[rnd];
        mPhotos[rnd] = tmpPhoto;

        // Return the index of which photo was swapped with the top:
        return rnd;
    }

    // Shuffle the order of the photos:
    public void Shuffle ()
    {  
        // Use the Fisher-Yates shuffle algorithm:
        for (int idx = 0; idx < mPhotos.Count; ++idx)
        {
            // Save the photo at idx:
            Photo tmpPhoto = mPhotos[idx];

            // Generate a next random index between idx (inclusive) and 
            // Length (noninclusive):
            int rnd = mRandom.Next(idx, mPhotos.Count);

            // Exchange photo at idx with randomly-chosen (later) photo:
            mPhotos[idx] = mPhotos[rnd];
            mPhotos[rnd] = tmpPhoto;
        }
    }
}

Then, modify the longClick Event to accept an position param:

public class PhotoViewHolder : RecyclerView.ViewHolder
{
    public ImageView Image { get; private set; }
    public TextView Caption { get; private set; }

    // Get references to the views defined in the CardView layout.
    public PhotoViewHolder (View itemView, Action<int> listener,Action<object,View.LongClickEventArgs,int> longClickListener) 
        : base (itemView)
    {
        // Locate and cache view references:
        Image = itemView.FindViewById<ImageView> (Resource.Id.imageView);
        Caption = itemView.FindViewById<TextView> (Resource.Id.textView);

        // Detect user clicks on the item view and report which item
        // was clicked (by position) to the listener:
        itemView.Click += (sender, e) => listener (base.Position);
        ItemView.LongClick +=(sender,e)=> longClickListener(sender,e,base.Position);
    }
}

Then start action mode with position param and inside OnActionItemClicked call the Remove function added to the Adapter:

void OnLongClick(object sender, View.LongClickEventArgs args,int position)
{
        mActionMode = new MyActionMode(mActivity,this,position);
        mode=mActivity.StartActionMode(mActionMode);
        ((View)sender).Selected = true;
        return;
}

...
public class MyActionMode : Java.Lang.Object, ActionMode.ICallback
{
    private Context mContext;
    private PhotoAlbumAdapter mAdapter;
    private int currentPosition;
    public MyActionMode(Context context):this(context,null,0)
    {

    }

    public MyActionMode(Context context, PhotoAlbumAdapter adapter,int position)
    {
        mContext = context;
        mAdapter = adapter;
        currentPosition = position;
    }

    public bool OnActionItemClicked(ActionMode mode, IMenuItem item)
    {
        switch (item.ItemId)
        {
            case Resource.Id.itemOneId:
                // do Delete
                mAdapter.RemoveAt(currentPosition);
                mAdapter.FinishActionMode();
                return true;
            case Resource.Id.itemTwoId:
                // do Update
                return true;
            default:
                return false;
        }
    }

    public bool OnCreateActionMode(ActionMode mode, IMenu menu)
    {
        mode.MenuInflater.Inflate(Resource.Menu.ContextualMenu, menu);
        return true;
    }

    public void OnDestroyActionMode(ActionMode mode)
    {
        mode.Dispose();
    }

    public bool OnPrepareActionMode(ActionMode mode, IMenu menu)
    {
        return false;
    }
}

I've committed the codes to demo project.

Notes: It is the same logic that can apply to the update operation.

来源：https://stackoverflow.com/questions/45929315/how-to-delete-row-in-recyclerlistview-on-click-of-menu-button-in-contextual-acti