How to Delete data in Firebase Realtime Database

• Create and Insert in Database Click Here
• Retrieve From database and show it on ListView Click Here
• Update data in Database Click Here

To Delete Data we need to use on item click listener on our ListView which we created.

When we click on the ListView item, it will return us a unique id that is created on our database at the time of the creation of a node. then on behalf of that unique specific node id, we will delete the specific value in the database.

Also, we create an Alert Dialog box with a delete button to delete our value.

MainActivity.java

 package studio.harpreet.firebasedatabase;  
 import androidx.annotation.NonNull;  
 import androidx.appcompat.app.AlertDialog;  
 import androidx.appcompat.app.AppCompatActivity;  
 import android.content.DialogInterface;  
 import android.os.Bundle;  
 import android.view.View;  
 import android.widget.AdapterView;  
 import android.widget.ArrayAdapter;  
 import android.widget.Button;  
 import android.widget.EditText;  
 import android.widget.LinearLayout;  
 import android.widget.ListView;  
 import android.widget.TextView;  
 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 MainActivity extends AppCompatActivity {  
   DatabaseReference databasestudent;  
   EditText roll_et,name_et,std_et;  
   Button add_btn;  
   ListView studentListView;  
   List<StudentModel > studentlist;  
   @Override  
   protected void onCreate(Bundle savedInstanceState) {  
     super.onCreate(savedInstanceState);  
     setContentView(R.layout.activity_main);  
     roll_et = findViewById(R.id.student_roll);  
     name_et = findViewById(R.id.student_name);  
     std_et = findViewById(R.id.student_std);  
     add_btn = findViewById(R.id.add_btn);  
     studentListView = findViewById(R.id.student_listview);  
     studentlist = new ArrayList<>();  
     databasestudent = FirebaseDatabase.getInstance().getReference("Student");  
     add_btn.setOnClickListener(new View.OnClickListener() {  
                     @Override  
                     public void onClick(View v) {  
                       addstudent(roll_et.getText().toString().trim(),  
                           name_et.getText().toString().trim(),  
                           std_et.getText().toString().trim());  
                     }  
                   });  
     studentListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {  
       @Override  
       public void onItemClick(AdapterView<?> parent, View view, final int position, long id) {  
         final StudentModel studentModel = studentlist.get(position);  
         AlertDialog.Builder builder = new AlertDialog.Builder(MainActivity.this);  
         LinearLayout layout = new LinearLayout(MainActivity.this);  
         layout.setOrientation(LinearLayout.VERTICAL);  
         final EditText name_et = new EditText(MainActivity.this);  
         layout.addView(name_et);  
         name_et.setHint("Name");  
         builder.setTitle("Update Name")  
             .setMessage("Write name to Update")  
             .setView(layout)  
             .setPositiveButton("Update", new DialogInterface.OnClickListener() {  
               @Override  
               public void onClick(DialogInterface dialog, int which) {  
                 DatabaseReference reference = FirebaseDatabase.getInstance().getReference("Student").child(studentModel.getId());  
                 StudentModel studentModel1 = new StudentModel(studentModel.getId(),studentModel.getRollno(),  
                     name_et.getText().toString().trim(),studentModel.getStd());  
                 reference.setValue(studentModel1);  
               }  
         }).setNegativeButton("Delete", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        DatabaseReference reference = FirebaseDatabase.getInstance().getReference("Student").child(studentModel.getId());

                        reference.removeValue();
                    }
                }).show();  
       }  
     });  
   }  
 private void addstudent(String Rollno, String Name, String Std)  
   {  
     String id = databasestudent.push().getKey();  
     StudentModel studentModel = new StudentModel(id,Rollno,Name,Std);  
     databasestudent.child(id).setValue(studentModel);  
   }  
   @Override  
   protected void onStart() {  
     super.onStart();  
     databasestudent.addValueEventListener(new ValueEventListener() {  
       @Override  
       public void onDataChange(@NonNull DataSnapshot dataSnapshot) {  
         studentlist.clear();  // because everytime when data updates in your firebase database it creates the list with updated items  
                     // so to avoid duplicate fields we clear the list everytime  
         if(dataSnapshot.exists())  
         {  
           for(DataSnapshot studentsnapshot : dataSnapshot.getChildren())  
           {  
             StudentModel studentModel = studentsnapshot.getValue(StudentModel.class);  
             studentlist.add(studentModel);  
           }  
           Student_ListAdaptor adaptor = new Student_ListAdaptor(MainActivity.this,studentlist);  
           studentListView.setAdapter(adaptor);  
         }  
       }  
       @Override  
       public void onCancelled(@NonNull DatabaseError databaseError) {  
       }  
     });  
   }  
 }  

It will successfully delete data in our Firebase Realtime Database and show it on a ListView

 

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