Question

我使用的是没有表单的API 27和Xamarin Android。

RecyclerView的基本用法已在本教程的上一步中进行了说明，下一步是通过Click-Handlers扩展示例。

我已使用以下代码public event EventHandler<int> ItemClick;扩展了我的适配器，并创建了这样的回调函数：

void OnItemClick (object sender, int position)
{
    Console.WriteLine("I've done it!");
}

并将其添加到适配器中，如下所示：

mAdapter = new CustomObjectAdapter(mCustomObject);
mAdapter.ItemClick += OnItemClick;

应用显示后，我在Console.WriteLine-Part上设置了一个Breckpoint，并触摸/单击了所显示的图像。但是该事件不会触发。

这是我的适配器类：

class ModuleClassContainerAdapter : RecyclerView.Adapter
    {
        public event EventHandler<int> ItemClick;
        public ModuleClassContainer mModuleClassContainer;

        public ModuleClassContainerAdapter(ModuleClassContainer moduleClassContainer)
        {
            mModuleClassContainer = moduleClassContainer;
        }

        public override int ItemCount
        {
            get { return mModuleClassContainer.NumModules; }
        }

        public override void OnBindViewHolder(RecyclerView.ViewHolder holder, int position)
        {
            ModuleViewHolder vh = holder as ModuleViewHolder;

            var imageBitmap = BitmapFactory.DecodeByteArray(mModuleClassContainer[position].ImageBytes, 0, mModuleClassContainer[position].ImageBytes.Length);

            // Load the photo image resource from the photo album:
            vh.Image.SetImageBitmap(imageBitmap);

            // Load the photo caption from the photo album:
            vh.Caption.Text = mModuleClassContainer[position].ModuleName;
        }

        public override RecyclerView.ViewHolder OnCreateViewHolder(ViewGroup parent, int viewType)
        {
            // Inflate the CardView for the photo:
            View itemView = LayoutInflater.From(parent.Context).
                        Inflate(Resource.Layout.ModuleCardView, parent, false);

            // Create a ViewHolder to hold view references inside the CardView:
            ModuleViewHolder vh = new ModuleViewHolder(itemView);
            return vh;
        }
    }

这是我设置适配器的方式：

private void SetupView()
        {
            RunOnUiThread(() =>
            {
                mModuleClassContainerAdapter = new ModuleClassContainerAdapter(mModuleClassContainer);
                mModuleClassContainerAdapter.ItemClick += MModuleClassContainerAdapter_ItemClick;
                mRecyclerView.SetAdapter(mModuleClassContainerAdapter);
                mModuleClassContainerAdapter.NotifyDataSetChanged();
            });
        }

为什么我的活动没有被触发？

Answer 1

在适配器中，声明eventHandler，并将其传递给ViewHolder

public class ModuleClassContainerAdapter  : RecyclerView.Adapter
    {
        // Event handler for item clicks:
        public event EventHandler<int> ItemClick;

// Create a new photo CardView (invoked by the layout manager): 
        public override RecyclerView.ViewHolder 
            OnCreateViewHolder (ViewGroup parent, int viewType)
        {
            // You need to pass the event 
            ModuleViewHolder vh = new ModuleViewHolder (itemView, OnClick); 
            return vh;
        }

        // Raise an event when the item-click takes place:
        void OnClick (int position)
        {
            if (ItemClick != null)
                ItemClick (this, position);
        }

在您的ViewHolder中

    public class ModuleViewHolder : RecyclerView.ViewHolder
    {
        // Get references to the views defined in the CardView layout.
        public ModuleViewHolder (View itemView, Action<int> listener) 
            : base (itemView)
        {
 on the item view and report which item
            // was clicked (by layout position) to the listener:
            itemView.Click += (sender, e) => listener (base.LayoutPosition);
        }
    }

为什么我的RecyclerView没有响应自定义的Click-Event？

1 个答案: