android - navigation drawer icon causing the custom toolbar text out from the center

Question

I am trying to center my toolbar text but Navigation drawer icon(Hamburger icon) causing my custom toolbar text little right from the center.

Without using Navigation drawer icon toolbar text is perfectly in the center.

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.v4.widget.DrawerLayout 
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:id="@+id/drawer_layout"
    android:layout_height="match_parent"
    android:fitsSystemWindows="true"
    tools:openDrawer="start"
    tools:context=".MainActivity">

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

        <android.support.v7.widget.Toolbar 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:id="@+id/toolbar"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:background="@color/colorPrimary"
    android:gravity="center_vertical|center_horizontal|center"
    android:minHeight="?attr/actionBarSize"
    app:contentInsetStart="0dp"
    app:subtitleTextColor="@color/colorWhite"
    app:titleTextColor="@color/colorWhite">

    <android.support.constraint.ConstraintLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:minHeight="?attr/actionBarSize">

        <TextView
            android:id="@+id/toolbar_title"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginBottom="8dp"
            android:layout_marginEnd="8dp"
            android:layout_marginRight="8dp"
            android:layout_marginTop="4dp"
            android:text="Main Title"
            android:textColor="@android:color/white"
            android:textSize="20sp"
            android:textStyle="bold"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent"
            app:layout_constraintVertical_bias="1.0" />

        <TextView
            android:id="@+id/toolbar_subtitle"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginBottom="8dp"
            android:layout_marginEnd="8dp"
            android:layout_marginRight="8dp"
            android:layout_marginTop="8dp"
            android:text="TextView"
            android:textColor="@android:color/white"
            android:textSize="16sp"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toBottomOf="@+id/toolbar_title"
            app:layout_constraintVertical_bias="1.0" />

        <!--    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Subtitle"
        android:gravity = "center"
        android:id="@+id/toolbar_Subtitle" />-->

    </android.support.constraint.ConstraintLayout>


</android.support.v7.widget.Toolbar>



    <android.support.design.widget.BottomNavigationView
        android:id="@+id/main_bottom_navigation"
        android:layout_width="match_parent"
        android:layout_height="56dp"
        android:layout_alignParentBottom="true"
        android:layout_alignParentStart="true"
        android:background="@color/colorPrimary"
        app:itemIconTint="@drawable/bottom_nav_colors"
        app:itemTextColor="@drawable/bottom_nav_colors"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:menu="@menu/navigation"
        android:layout_alignParentLeft="true" />

    <FrameLayout
        android:id="@+id/home_frame"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_alignParentStart="true"
        android:layout_alignParentTop="true"
        android:layout_marginBottom="55dp"
        android:layout_marginTop="55dp">

    </FrameLayout>

</RelativeLayout>
    <android.support.design.widget.NavigationView
        android:id="@+id/nav_view"
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:layout_gravity="start"
        android:fitsSystemWindows="true"
        android:background="@color/colorWhite"
        app:itemTextColor="@color/colorBlack"

        app:headerLayout="@layout/nav_header_main"
        app:menu="@menu/activity_main_drawer" />

</android.support.v4.widget.DrawerLayout>

In MainActivity.java i am using following code to enable the custom toobar

toolbar=(Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
getSupportActionBar().setDisplayShowTitleEnabled(false);