如何从 Android 中的 Firebase 实时数据库中删除数据？

在本文中，我们将看到如何删除 Firebase 实时数据库中添加的数据。因此，我们将转向在 Android Firebase 中实现此删除数据。

我们将在本文中构建什么？

当用户长按 RecyclerView 项目时，我们将显示一个简单的 AlertBox。它将有两个选择。 （删除和取消）。当用户单击删除时，它只会删除该值。您可以参考如何在 Android 中将数据保存到 Firebase 实时数据库以了解如何在 Firebase 中保存数据。

Note: You can use Hashmap to save data in firebase.

此外，您还可以直接在 firebase 中添加数据，如下所示

分步实施

第 1 步：创建一个新项目

要在 Android Studio 中创建新项目，请参阅如何在 Android Studio 中创建/启动新项目。请注意，选择Java作为编程语言。

步骤 2：使用 activity_main.xml 文件

导航到app > res > layout > activity_main.xml并将以下代码添加到该文件中。下面是activity_main.xml文件的代码。

第 3 步：使用 DModel。 Java文件

转到DModel。 Java文件，参考如下代码。下面是DModel的代码。 Java文件。

Java

package com.anni.uploaddataexcelsheet;
 
public class DModel {
    public DModel() {
    }
 
    public String getTime() {
        return time;
    }
 
    public DModel(String time, String name) {
        this.time = time;
        this.name = name;
    }
 
    public void setTime(String time) {
        this.time = time;
    }
 
    String time;
    public DModel(String name) {
        this.name = name;
    }
 
    public String getName() {
        return name;
    }
 
    public void setName(String name) {
        this.name = name;
    }
 
    String name;
}

第 4 步：使用 DAdapter。 Java文件

转到DAdapter。 Java文件，参考如下代码。下面是DAdapter的代码。 Java文件

Java

package com.anni.uploaddataexcelsheet;
 
import android.app.AlertDialog;
import android.content.Context;
import android.content.DialogInterface;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
 
import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;
 
import com.google.firebase.auth.FirebaseAuth;
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 java.util.List;
 
public class DAdapter extends RecyclerView.Adapter {
 
    List notifications;
 
    public DAdapter(List notifications, Context context) {
        this.notifications = notifications;
        this.context = context;
    }
 
    Context context;
 
    @NonNull
    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View view= LayoutInflater.from(parent.getContext()).inflate(R.layout.row_delete,parent,false);
        return new MyHolder(view);
    }
 
    @Override
    public void onBindViewHolder(@NonNull final RecyclerView.ViewHolder holder, final int position) {
 
          // get the item value by positions
        String text=notifications.get(position).getName();
        final String time=notifications.get(position).getTime();
        ((MyHolder)holder).notification.setText(text);
           
          // click on item to be deleted
        ((MyHolder)holder).notification.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                CharSequence options[]=new CharSequence[]{
                          // select any from the value
                        "Delete",
                        "Cancel",
                };
                AlertDialog.Builder builder=new AlertDialog.Builder(holder.itemView.getContext());
                builder.setTitle("Delete Content");
                builder.setItems(options, new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                          // if delete option is choosed
                          // then call delete function
                        if(which==0) {
                            delete(position,time);
                        }
 
                    }
                });
                builder.show();
            }
        });
 
    }
 
    private void delete(int position, String time) {
          // creating a variable for our Database
        // Reference for Firebase.
        DatabaseReference dbref= FirebaseDatabase.getInstance().getReference().child("DataValue");
      // we are use add listerner
      // for event listener method
      // which is called with query.  
      Query query=dbref.child(time);
        query.addListenerForSingleValueEvent(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                // remove the value at reference
                dataSnapshot.getRef().removeValue();
            }
 
            @Override
            public void onCancelled(@NonNull DatabaseError databaseError) {
 
            }
        });
    }
 
 
    @Override
    public int getItemCount() {
        return notifications.size();
    }
    class MyHolder extends RecyclerView.ViewHolder{
 
        TextView notification;
        public MyHolder(@NonNull View itemView) {
            super(itemView);
            notification=itemView.findViewById(R.id.name);
        }
    }
}

第 6 步：使用 MainActivity。 Java文件

转到主活动。 Java文件，参考如下代码。下面是MainActivity的代码。 Java文件

Java

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;
 
import android.os.Bundle;
 
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.ValueEventListener;
 
import java.util.ArrayList;
import java.util.List;
 
public class DeleteData extends AppCompatActivity {
    List notifications;
    DAdapter adapterNotification;
 
    RecyclerView recyclerView;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_delete_data);
           
        // Initialise layout
        recyclerView=findViewById(R.id.recyclerview);
        LinearLayoutManager linearLayoutManager=new LinearLayoutManager(DeleteData.this);
           
        // reverse tha layout
        linearLayoutManager.setReverseLayout(true);
        recyclerView.setHasFixedSize(true);
        recyclerView.setLayoutManager(linearLayoutManager);
        notifications=new ArrayList<>();
         
         // creating a variable for our Database
        // Reference for Firebase.
        DatabaseReference reference= FirebaseDatabase.getInstance().getReference("DataValue");
     
      // we are using add value event listener method
      // which is called with database reference.
      reference.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                // clear the data
                notifications.clear();
                for (DataSnapshot dataSnapshot1:dataSnapshot.getChildren()) {
                    DModel modelNotification = dataSnapshot1.getValue(DModel.class);
                    notifications.add(modelNotification);
                    adapterNotification = new DAdapter(notifications,DeleteData.this);
                    // set the adapter
                    recyclerView.setAdapter(adapterNotification);
                    adapterNotification.notifyDataSetChanged();
                }
            }
 
            @Override
            public void onCancelled(@NonNull DatabaseError databaseError) {
 
            }
        });
    }
}

数据库结构

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