导航抽屉图标导致自定义工具栏文本从中心移出

Question

我试图居中放置工具栏文本，但是导航抽屉图标（汉堡图标）导致我的自定义工具栏文本居中对齐。

在不使用导航抽屉图标工具栏文本的情况下，文本恰好位于中间。

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>

在MainActivity.java中，我正在使用以下代码来启用自定义工具栏

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