从回收站视图和 Firebase 中删除行

Question

在回收站视图中滑动时，我试图从 firebase 中删除 arow。我已经设法从回收站视图中删除了该记录，但正在努力从 Firebase 中删除它。以下是我目前正在使用的，在 deleteItem() 方法（在 getSnapshots() 方法上（无法解析方法 'getSnapshots()'）的 adpater 中出现错误。

我在回收站视图中使用 Item touch helper 的活动：

protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_customer_profile);
 Log.d(TAG, "finding recyclerview");
        recyclerView = (RecyclerView) findViewById(R.id.myRecyclerBooking);
        recyclerView.setLayoutManager( new LinearLayoutManager(this));


        Log.d(TAG, "getting db reference");



        //FirebaseSearch https://www.youtube.com/watch?v=b_tz8kbFUsU
        reference = FirebaseDatabase.getInstance().getReference().child("Booking");
        Query firebaseSearchQuery = reference.orderByChild("customerID").equalTo(mAuth.getCurrentUser().getUid());

        firebaseSearchQuery.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                Log.d(TAG, "populating recyclerview");

                list = new ArrayList<Booking>();
                for (DataSnapshot dataSnapshot1 : dataSnapshot.getChildren()) {
                    Booking b = dataSnapshot1.getValue(Booking.class);
                    list.add(b);
                }
                adapter = new MyAdapterBookings(CustomerProfile.this, list);
                recyclerView.setAdapter(adapter);
                adapter.notifyDataSetChanged();
            }


            @Override
            public void onCancelled(@NonNull DatabaseError databaseError) {
                Toast.makeText(CustomerProfile.this, "Opsss.... Something is wrong", Toast.LENGTH_SHORT).show();
            }
        });
}

ItemTouchHelper.SimpleCallback itemTouchHelperCallback = new RecyclerItemTouchHelper(0, ItemTouchHelper.LEFT, this);
        new ItemTouchHelper(itemTouchHelperCallback).attachToRecyclerView(recyclerView);



        ItemTouchHelper.SimpleCallback itemTouchHelperCallback1 = new ItemTouchHelper.SimpleCallback(0, ItemTouchHelper.LEFT | ItemTouchHelper.RIGHT | ItemTouchHelper.UP) {
            @Override
            public boolean onMove(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, RecyclerView.ViewHolder target) {
                return false;
            }

            @Override
            public void onSwiped(RecyclerView.ViewHolder viewHolder, int direction) {
                // Row is swiped from recycler view
                // remove it from adapter
            }

            @Override
            public void onChildDraw(Canvas c, RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, float dX, float dY, int actionState, boolean isCurrentlyActive) {
                super.onChildDraw(c, recyclerView, viewHolder, dX, dY, actionState, isCurrentlyActive);
            }
        };

        // attaching the touch helper to recycler view
        new ItemTouchHelper(itemTouchHelperCallback1).attachToRecyclerView(recyclerView);
    }

@Override
    public void onSwiped(RecyclerView.ViewHolder viewHolder, int direction, int position) {

        if (viewHolder instanceof MyAdapterBookings.MyViewHolder) {
            // get the removed item name to display it in snack bar
            String name = list.get(viewHolder.getAdapterPosition()).getMuaName();

            // backup of removed item for undo purpose
            final Booking deletedItem = list.get(viewHolder.getAdapterPosition());
            final int deletedIndex = viewHolder.getAdapterPosition();

            // remove the item from recycler view
            adapter.removeItem(viewHolder.getAdapterPosition());
            adapter.deleteItem(viewHolder.getAdapterPosition());


            // showing snack bar with Undo option
            Snackbar snackbar = Snackbar
                    .make(coordinatorLayout, "Appointment with " + name + " cancelled!", Snackbar.LENGTH_LONG);
            snackbar.setAction("UNDO", new View.OnClickListener() {
                @Override
                public void onClick(View view) {

                    // undo is selected, restore the deleted item
                    adapter.restoreItem(deletedItem, deletedIndex);
                }
            });
            snackbar.setActionTextColor(Color.YELLOW);
            snackbar.show();
        }

    }

我的适配器：

import android.content.Context;
import android.content.Intent;
import android.os.Handler;
import android.support.annotation.NonNull;
import android.support.v7.widget.RecyclerView;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.RelativeLayout;
import android.widget.TextView;
import android.widget.Toast;

import com.google.android.gms.tasks.OnCompleteListener;
import com.google.android.gms.tasks.Task;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.Query;
import com.google.firebase.database.ValueEventListener;
import com.squareup.picasso.Picasso;

import java.util.ArrayList;

public class MyAdapterBookings extends RecyclerView.Adapter<MyAdapterBookings.MyViewHolder> {

    Context context;
    ArrayList<Booking> bookings;
    DatabaseReference reference;
    private static final String TAG = "Bookings Adapter";
    public MyAdapterBookings(Context c , ArrayList<Booking> b)
    {
        context = c;
        bookings = b;
    }

    @NonNull
    @Override
    public MyViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        return new MyViewHolder(LayoutInflater.from(context).inflate(R.layout.bookingview,parent,false));
    }

    @Override
    public void onBindViewHolder(@NonNull MyViewHolder holder, int position) {
        holder.name.setText(bookings.get(position).getMuaName());
        holder.date.setText(bookings.get(position).getDate());
        holder.time.setText(bookings.get(position).getTime());
        holder.price.setText(bookings.get(position).getPrice());
        holder.location.setText(bookings.get(position).getLocation());

    }

    @Override
    public int getItemCount() {
        return bookings.size();
    }

    class MyViewHolder extends RecyclerView.ViewHolder
    {
        TextView name,date,time,price,location;
        public RelativeLayout viewBackground, viewForeground;
        public MyViewHolder(View itemView) {
            super(itemView);
            name = (TextView) itemView.findViewById(R.id.name);
            date = (TextView) itemView.findViewById(R.id.date);
            time = (TextView) itemView.findViewById(R.id.time);
            price = (TextView) itemView.findViewById(R.id.price);
            location = (TextView) itemView.findViewById(R.id.location);

            viewBackground = itemView.findViewById(R.id.view_background);
            viewForeground = itemView.findViewById(R.id.view_foreground);



        }    }



    public void removeItem(int position) {
        bookings.remove(position);
        // notify the item removed by position
        // to perform recycler view delete animations
        // NOTE: don't call notifyDataSetChanged()
        notifyItemRemoved(position);


}


public void deleteItem(int position){

    getSnapshots().getSnapshot(position).getReference().delete();
}

public void restoreItem(Booking item, int position) {
        bookings.add(position, item);
        // notify item added by position
        notifyItemInserted(position);
    }



}

Answer 1

要从 Firebase 实时数据库中删除节点，您需要参考其准确、完整的路径。当您加载数据时，您有这样的参考。例如在onDataChange 你可以删除每个节点：

public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
    for (DataSnapshot dataSnapshot1 : dataSnapshot.getChildren()) {
        //Booking b = dataSnapshot1.getValue(Booking.class);
        dataSnapshot1.getRef().removeValue();
    }
}

当然，这不是您想要做的，但它显示了从 Firebase 中删除的工作原理。您需要知道要删除的节点的完整路径，包括该子节点的键。

在您的侦听器中，您从每个子节点获取 value 并将其添加到列表中，然后将其显示在适配器中。但是您没有获得每个子节点的 key。这意味着您的列表/适配器仅具有删除节点所需的部分知识。当您的 deleteItem 函数被调用并使用要删除的项目的位置时，无法再查找该节点的 key。

因此，您需要跟踪适配器中子节点的键和值。一种常见的方法是保留两个列表：一个带有键，一个带有值。

所以首先你为你的适配器的键添加一个List<String>：

ArrayList<Booking> bookings;
ArrayList<String> keys;

并在适配器的构造函数中接受：

public MyAdapterBookings(Context c , ArrayList<Booking> b, ArrayList<String> k)
{
    context = c;
    bookings = b;
    keys = k;
}

然后在onDataChange中添加每个键：

public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
    Log.d(TAG, "populating recyclerview");

    list = new ArrayList<Booking>();
    List<String> keys = new ArrayList<String>();
    for (DataSnapshot dataSnapshot1 : dataSnapshot.getChildren()) {
        Booking b = dataSnapshot1.getValue(Booking.class);
        list.add(b);
        keys.add(dataSnapshot1.getKey());
    }
    adapter = new MyAdapterBookings(CustomerProfile.this, list, keys);
    recyclerView.setAdapter(adapter);
    adapter.notifyDataSetChanged();
}

最后您可以查找要删除的项目的键：

public void deleteItem(int position){
    String key = keys.get(position);
    DatabaseReference ref = FirebaseDatabase.getInstance().getReference().child("Booking");
    ref.child(key).removeValue();
}