Berikut merupakan code untuk menampilkan data dari firebase ke android

activity_get_data_firebase.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#bb013d60"
    android:padding="16dp"
    android:gravity="center">
    <TextView
        android:id="@+id/title"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Result Data Firebase"
        android:padding="10dp"
        android:textSize="30sp"
        android:textColor="#fff"
        android:textStyle="bold|italic"
        android:layout_marginBottom="20dp"
        android:layout_centerHorizontal="true"/>
    <Button
        android:id="@+id/btnBack"
        android:layout_alignParentBottom="true"
        android:background="#dc304a9f"
        android:textColor="#fff"
        android:layout_marginRight="70dp"
        android:layout_marginLeft="70dp"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="24dp"
        android:text="Kembali"/>
    <ListView
        android:layout_above="@id/btnBack"
        android:id="@+id/listview"
        android:layout_below="@id/title"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

    </ListView>

</RelativeLayout>

GetFirebaseActivity.java

public class GetFirebaseActivity extends Activity implements AdapterView.OnItemClickListener {

    Activity activity;
    ListView listView;
    ListAdapter adapter;
    private ArrayList<HashMap<String, String>> list = new ArrayList<HashMap<String, String>>();
    Button btnBack;
    DatabaseReference rootRef,demoRef;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_get_data_firebase);
        activity = this;
        btnBack = (Button) findViewById(R.id.btnBack);
        listView = findViewById(R.id.listview);
        listView.setOnItemClickListener(this);
        listView.setOverScrollMode(View.OVER_SCROLL_NEVER);

        rootRef = FirebaseDatabase.getInstance().getReference();
        demoRef = rootRef.child("demo");
        btnBack.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                onBackPressed();
            }
        });

        getDataValue();

    }

    @Override
    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {

    }

    public void getDataValue(){
        list = new ArrayList<HashMap<String, String>>();
        rootRef.child("demo")
                .addListenerForSingleValueEvent(new ValueEventListener() {
                    @Override
                    public void onDataChange(DataSnapshot dataSnapshot) {
                        int i = 1;
                        for (DataSnapshot snapshot : dataSnapshot.getChildren()) {
                            String id = (String) snapshot.getKey();
                            String textTitle = (String) snapshot.child("textTitle").getValue();
                            String textInput = (String) snapshot.child("textInput").getValue();
                            String date = (String) snapshot.child("date").getValue();

                            HashMap<String, String> data = new HashMap<>();
                            data.put("key", id);
                            data.put("nomor", ""+i++);
                            data.put("textTitle", textTitle);
                            data.put("textInput", textInput);
                            data.put("date", date);
                            list.add(data);
                        }

                        adapter = new ListAdapter(activity, list,
                                R.layout.list_item, new String[]{"nomor","textTitle","textInput", "date"},
                                new int[]{R.id.nomor, R.id.textTitle,R.id.textInput, R.id.date});
                        Parcelable state = listView.onSaveInstanceState();
                        listView.setAdapter(adapter);
                        listView.onRestoreInstanceState(state);
                        adapter.notifyDataSetChanged();
                    }
                    @Override
                    public void onCancelled(DatabaseError databaseError) {
                    }
                });
    }

    public class ListAdapter extends SimpleAdapter {
        private Context mContext;
        public LayoutInflater inflater = null;

        public ListAdapter(Context context, List<? extends Map<String, ?>> data, int resource, String[] from, int[] to) {
            super(context, data, resource, from, to);
            mContext = context;
            inflater = (LayoutInflater) mContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        }

        @Override
        public View getView(int position, View convertView, ViewGroup parent) {
            View vi = convertView;
            if (convertView == null)
                vi = inflater.inflate(R.layout.list_item, null);

            HashMap<String, Object> data = (HashMap<String, Object>) getItem(position);
            final Button btnDelete = vi.findViewById(R.id.delete);
            final TextView nomor = vi.findViewById(R.id.nomor);
            final TextView textTitle = vi.findViewById(R.id.textTitle);
            final TextView textInput = vi.findViewById(R.id.textInput);
            final TextView date = vi.findViewById(R.id.date);

            final String strKey = (String) data.get("key");
            final String strID = (String) data.get("nomor");
            final String strTextTitle = (String) data.get("textTitle");
            final String strTextInput = (String) data.get("textInput");
            final String strDate = (String) data.get("date");

            nomor.setText(strID);
            textTitle.setText(strTextTitle);
            textInput.setText(strTextInput);
            date.setText(strDate);

            btnDelete.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                   Delete(strKey);
                }
            });

            return vi;
        }

    }

public void Delete(String keyID){
    Query applesQuery = demoRef.child(keyID);

    applesQuery.addListenerForSingleValueEvent(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            for (DataSnapshot dummySnapshot: dataSnapshot.getChildren()) {
                dummySnapshot.getRef().removeValue();
            }
            getDataValue();
        }

        @Override
        public void onCancelled(DatabaseError databaseError) {
            Log.e("delete", "onCancelled", databaseError.toException());
        }
    });
}


    @Override
    public void onBackPressed() {
        super.onBackPressed();
    }
}

list_item.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/item"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:background="@android:color/transparent"
    android:paddingLeft="10dp"
    android:paddingTop="5dp"
    android:paddingRight="10dp"
    android:paddingBottom="5dp">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="#acc5e0ef"
        android:orientation="vertical"
        android:padding="7dp">

        <RelativeLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content">

            <TextView
                android:id="@+id/nomor"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:paddingLeft="15dp"
                android:paddingTop="5dp"
                android:paddingRight="0dp"
                android:paddingBottom="5dp"
                android:textStyle="bold"
                android:textColor="#250000"
                android:text="1." />

            <Button
                android:id="@+id/delete"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_alignParentRight="true"
                android:layout_centerVertical="true"
                android:background="#b67474"
                android:paddingLeft="0dp"
                android:paddingTop="5dp"
                android:paddingRight="0dp"
                android:paddingBottom="0dp"
                android:text="hapus"
                android:textColor="#fcfafa"
                android:textSize="18sp"
                android:textStyle="normal" />

            <RelativeLayout
                android:layout_toRightOf="@id/nomor"
                android:layout_toLeftOf="@id/delete"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content">

                <TextView
                    android:id="@+id/textTitle"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:layout_alignParentLeft="true"
                    android:paddingLeft="15dp"
                    android:paddingTop="5dp"
                    android:paddingRight="5dp"
                    android:paddingBottom="5dp"
                    android:text="Text"
                    android:textColor="#250000"
                    android:textStyle="bold" />

                <TextView
                    android:id="@+id/textInput"
                    android:layout_below="@id/textTitle"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:layout_alignParentLeft="true"
                    android:paddingLeft="15dp"
                    android:paddingTop="5dp"
                    android:paddingRight="5dp"
                    android:paddingBottom="5dp"
                    android:text="Text"
                    android:textColor="#250000" />

                <TextView
                    android:id="@+id/date"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:layout_below="@id/textInput"
                    android:layout_alignParentLeft="true"
                    android:paddingLeft="15dp"
                    android:paddingTop="5dp"
                    android:paddingRight="5dp"
                    android:paddingBottom="5dp"
                    android:text="Date"
                    android:textColor="#250000" />

            </RelativeLayout>
        </RelativeLayout>
    </LinearLayout>
</LinearLayout>