How to add a hint to Spinner in Android

<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/rl"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:padding="10dp"
    tools:context=".MainActivity"
    android:background="#60c4ff"
    >
    <Spinner
        android:id="@+id/spinner"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        />
</RelativeLayout>

<?xml version="1.0" encoding="utf-8"?>
<TextView
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:padding="10dp"
    android:textStyle="italic"
    android:fontFamily="sans-serif-medium"
    />

package com.jigopost.spinner;

import android.graphics.Color;
import android.os.Bundle;
import android.app.Activity;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Spinner;
import android.widget.TextView;
import android.widget.Toast;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;


public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        // Get reference of widgets from XML layout
        final Spinner spinner = (Spinner) findViewById(R.id.spinner);

        // Initializing a String Array
        String[] plants = new String[]{
                "Select an item...",
                "California sycamore",
                "Mountain mahogany",
                "Butterfly weed",
                "Carrot weed"
        };

        final List<String> plantsList = new ArrayList<>(Arrays.asList(plants));

        // Initializing an ArrayAdapter
        final ArrayAdapter<String> spinnerArrayAdapter = new ArrayAdapter<String>(
                this,R.layout.spinner_item,plantsList){
            @Override
            public boolean isEnabled(int position){
                if(position == 0)
                {
                    // Disable the first item from Spinner
                    // First item will be use for hint
                    return false;
                }
                else
                {
                    return true;
                }
            }
            @Override
            public View getDropDownView(int position, View convertView,
                                        ViewGroup parent) {
                View view = super.getDropDownView(position, convertView, parent);
                TextView tv = (TextView) view;
                if(position == 0){
                    // Set the hint text color gray
                    tv.setTextColor(Color.GRAY);
                }
                else {
                    tv.setTextColor(Color.BLACK);
                }
                return view;
            }
        };
        spinnerArrayAdapter.setDropDownViewResource(R.layout.spinner_item);
        spinner.setAdapter(spinnerArrayAdapter);

        spinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
            @Override
            public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
                String selectedItemText = (String) parent.getItemAtPosition(position);
                // If user change the default selection
                // First item is disable and it is used for hint
                if(position > 0){
                    // Notify the selected item text
                    Toast.makeText
                            (getApplicationContext(), "Selected : " + selectedItemText, Toast.LENGTH_SHORT)
                            .show();
                }
            }

            @Override
            public void onNothingSelected(AdapterView<?> parent) {

            }
        });
   }
}