Listview

package com.example.listview;

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.text.TextUtils;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.Toast;

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;

public class MainActivity extends AppCompatActivity {
    private EditText edit;
    private Button add;
    private ListView listview;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        edit=findViewById(R.id.edit);
        add=findViewById(R.id.add);
        add.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String textedit=edit.getText().toString();
                if(TextUtils.isEmpty(textedit)){
                    Toast.makeText(MainActivity.this, "Please Insert Text ", Toast.LENGTH_SHORT).show();
                }
                else {
                    FirebaseDatabase.getInstance().getReference().child("Programming Knowledge").child("language").push().setValue(textedit);
                }
            }
        });
        listview=findViewById(R.id.list);
        ArrayList<String>list=new ArrayList<>();
        ArrayAdapter adapter=new ArrayAdapter<String>(this, R.layout.activity_main,list);
        listview.setAdapter(adapter);
        DatabaseReference reference=FirebaseDatabase.getInstance().getReference().child("language");
        reference.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot snapshot) {
                for(DataSnapshot dataSnapshot:snapshot.getChildren()){
                    list.clear();
                    list.add(dataSnapshot.getValue().toString());
                }
                adapter.notifyDataSetChanged();
            }

            @Override
            public void onCancelled(@NonNull DatabaseError error) {

            }
        });

    }
}