How to delete data in ListView and also from Firebase?

Question

I am working on an Android Application that saves the medicine Inventory in Firebase. All Inventory saved on Firebase perfectly. The Links i have visited are this this I showed all inventory in the list in the Android. Now What I want to do is delete the data item from the list by having a button again every list Item. Here is my XML code of list view

<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:background="@drawable/bgcolor"
android:layout_height="match_parent">

<RelativeLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_margin="10dp"
    android:background="@drawable/bgcolor">

    <TextView
        android:id="@+id/tvmediname"
        android:layout_width="250dp"
        android:layout_height="wrap_content"
        android:layout_below="@+id/tvname"
        android:layout_marginTop="14dp"
        android:paddingLeft="15dp"
        android:text="Name"
        android:textSize="20sp"
        tools:ignore="UnknownId" />

    <TextView
        android:id="@+id/tvmediusage"
        android:layout_width="250dp"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/tvmediname"
        android:layout_alignStart="@+id/tvmediname"
        android:layout_below="@+id/tvmediname"
        android:paddingLeft="15dp"
        android:text="Usage"
        android:textSize="20sp" />

    <TextView
        android:id="@+id/tvmedigenre"
        android:layout_width="250dp"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/tvmediname"
        android:layout_alignStart="@+id/tvmediname"
        android:layout_below="@+id/tvmediusage"
        android:paddingLeft="15dp"
        android:text="Company"
        android:textSize="20sp" />

    <TextView
        android:id="@+id/tvexpdate"
        android:layout_width="250dp"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:layout_below="@+id/tvmedigenre"
        android:paddingLeft="15dp"
        android:text="Expiry Date"
        android:textSize="20sp" />

    <ImageButton
        android:id="@+id/btndelete"
        android:layout_width="90sp"
        android:layout_height="100sp"
        android:layout_alignParentEnd="true"
        android:layout_alignParentRight="true"
        android:layout_centerVertical="true"
        app:srcCompat="@drawable/btndelt" />

</RelativeLayout>

Here is my retrieve activity that Retrieves the data From Firebase

public class RetreiveActivity extends AppCompatActivity {
ListView mylistView;
DatabaseReference db;
List<ClassMedicine> medicineList;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_retreive);
    mylistView= findViewById(R.id.mylist);
    medicineList= new ArrayList<>();
    db= FirebaseDatabase.getInstance().getReference("medicines");

}

@Override
protected void onStart() {
    super.onStart();
    db.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            medicineList.clear();
            for (DataSnapshot medicineSnapshot:dataSnapshot.getChildren()){
                ClassMedicine classMedicine=medicineSnapshot.getValue(ClassMedicine.class);
                medicineList.add(classMedicine);
            }
            MedicineList adapter=new MedicineList(RetreiveActivity.this,medicineList);
            mylistView.setAdapter(adapter);
        }

        @Override
        public void onCancelled(DatabaseError databaseError) {

        }
    });
}

}

Here is my Model Class

public class ClassMedicine {
String medicineId;
String medicineName;
String medicineUsage;
String medicineGenre;
String mediDate;

public ClassMedicine(){
}
public ClassMedicine(String medicineId, String medicineName, String medicineUsage, String medicineGenre,String mediDate) {
    this.medicineId = medicineId;
    this.medicineName = medicineName;
    this.mediDate= mediDate;
    this.medicineUsage = medicineUsage;
    this.medicineGenre = medicineGenre;
}

public String getMedicineId() {
    return medicineId;
}

public String getMedicineName() {
    return medicineName;
}

public String getMedicineUsage() {
    return medicineUsage;
}

public String getMedicineGenre() {
    return medicineGenre;
}
public String getMediDate() {
    return mediDate;
}

}

Here is my List Activity

public class MedicineList extends ArrayAdapter<ClassMedicine> {
private Activity context;
private List<ClassMedicine> medicineList;
public MedicineList(Activity context,List<ClassMedicine> medicineList){
    super(context,R.layout.mylistlayout,medicineList);
    this.context=context;
    this.medicineList=medicineList;
}

@NonNull
@Override
public View getView(int position, @Nullable View convertView, @NonNull ViewGroup parent) {
    LayoutInflater inflater= context.getLayoutInflater();
    View listViewItems= inflater.inflate(R.layout.mylistlayout,null,true);
    TextView textViewName=listViewItems.findViewById(R.id.tvmediname);
    TextView textViewGenre=listViewItems.findViewById(R.id.tvmedigenre);
    TextView textViewUsage=listViewItems.findViewById(R.id.tvmediusage);
    TextView textViewDate= listViewItems.findViewById(R.id.tvexpdate);
    ClassMedicine classMedicine= medicineList.get(position);
    textViewName.setText(classMedicine.getMedicineName());
    textViewGenre.setText(classMedicine.getMedicineGenre());
    textViewUsage.setText(classMedicine.getMedicineUsage());
    textViewDate.setText(classMedicine.getMediDate());
    return listViewItems;
}

}

I want to do to delete a particular list Item from List. As the list item is deleted that particular data should also remove from the firebase

Answer 1

First you need to change the implementation of your adapter class, create an inner ViewHolder class like below

public class ViewHolder {
        TextView textViewName;
        TextView textViewGenre;
        TextView textViewUsage;
        TextView textViewDate;
        ImageButton btnDelete;
        View itemView;
        int position;

        public ViewHolder(View view) {
            itemView = view;
            textViewName = view.findViewById(R.id.tvmediname);
            textViewGenre = view.findViewById(R.id.tvmedigenre);
            textViewUsage = view.findViewById(R.id.tvmediusage);
            textViewDate = view.findViewById(R.id.tvexpdate);
            btnDelete = view.findViewById(R.id.btndelete);

            // initialize all your views

        }

        public void setPosition(int position) {
            this.position = position;
        }


        public void bindViews() {
            ClassMedicine classMedicine = medicineList.get(position)
            textViewName.setText(classMedicine.getMedicineName());
            textViewGenre.setText(classMedicine.getMedicineGenre());
            textViewUsage.setText(classMedicine.getMedicineUsage());
            textViewDate.setText(classMedicine.getMediDate());
            btnDelete.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                   onDeleteItem(position);
                }
            });
        }

    }

Add below method in your adapter class

private void onDeleteItem(int position) {
           ClassMedicine classMedicine = medicineList.get(position);
                DatabaseReference db = FirebaseDatabase.getInstance().getReference("medicines");
                db.child("medicines").addListenerForSingleValueEvent(new ValueEventListener() {
                    @Override
                    public void onDataChange(DataSnapshot dataSnapshot) {
                        for (DataSnapshot snapshot : dataSnapshot.getChildren()) {
                            ClassMedicine medicine = snapshot.getValue(ClassMedicine.class);
                            if (classMedicine.getMedicineId().equals(medicine.getMedicineId())) {
                                databaseReference.child("medicines").child(snapshot.getKey().toString()).removeValue();
                                medicineList.remove(position);
                                notifyDataSetChanged();
                                break;
                            }
                        }
                    }
                });
            }

Then modify your getView method accordingly

@Override
public View getView(int position, @Nullable View convertView, @NonNull ViewGroup parent) {
        ViewHolder holder;
        if (convertView == null) {
            LayoutInflater inflater= context.getLayoutInflater();
            convertView = inflater.inflate(R.layout.mylistlayout,null,true);
            holder = new ViewHolder(convertView);
            convertView.setTag(holder);
        }
        else {
            holder = (ViewHolder) convertView.getTag();
        }
        holder.setPosition(position);
        holder.bindViews();
        return convertView;
}

Note : I have just written as pseudo code but should work

Here is the final adapter class, it is for you to avoid confustion

public class MedicineList extends ArrayAdapter<ClassMedicine> {
    private Activity context;
    private List<ClassMedicine> medicineList;
    public MedicineList(Activity context,List<ClassMedicine> medicineList){
        super(context,R.layout.mylistlayout,medicineList);
        this.context=context;
        this.medicineList=medicineList;
    }

    @NonNull
    @Override
    public View getView(int position, @Nullable View convertView, @NonNull ViewGroup parent) {
        ViewHolder holder;
        if (convertView == null) {
            LayoutInflater inflater= context.getLayoutInflater();
            convertView = inflater.inflate(R.layout.mylistlayout,null,true);
            holder = new ViewHolder(convertView);
            convertView.setTag(holder);
        }
        else {
            holder = (ViewHolder) convertView.getTag();
        }
        holder.setPosition(position);
        holder.bindViews();
        return convertView;
    }

    public class ViewHolder {
        TextView textViewName;
        TextView textViewGenre;
        TextView textViewUsage;
        TextView textViewDate;
        ImageButton btnDelete;
        View itemView;
        int position;

        public ViewHolder(View view) {
            itemView = view;
            textViewName = view.findViewById(R.id.tvmediname);
            textViewGenre = view.findViewById(R.id.tvmedigenre);
            textViewUsage = view.findViewById(R.id.tvmediusage);
            textViewDate = view.findViewById(R.id.tvexpdate);
            btnDelete = view.findViewById(R.id.btndelete);

            // initialize all your views

        }

        public void setPosition(int position) {
            this.position = position;
        }


        public void bindViews() {
            ClassMedicine classMedicine = medicineList.get(position)
            textViewName.setText(classMedicine.getMedicineName());
            textViewGenre.setText(classMedicine.getMedicineGenre());
            textViewUsage.setText(classMedicine.getMedicineUsage());
            textViewDate.setText(classMedicine.getMediDate());
            btnDelete.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                   onDeleteItem(position);
                }
            });
        }

    }

    private void onDeleteItem(int position) {
        ClassMedicine classMedicine = medicineList.get(position);
        DatabaseReference db = FirebaseDatabase.getInstance().getReference("medicines");
        db.child("medicines").addListenerForSingleValueEvent(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                for (DataSnapshot snapshot : dataSnapshot.getChildren()) {
                    ClassMedicine medicine = snapshot.getValue(ClassMedicine.class);
                    if (classMedicine.getMedicineId().equals(medicine.getMedicineId())) {
                        databaseReference.child("medicines").child(snapshot.getKey().toString()).removeValue();
                        medicineList.remove(position);
                        notifyDataSetChanged();
                        break;
                    }
                }
            }
        });
    }

}