导航抽屉片段影响工具栏的样式和位置

So after a week of solid research, I have finally manage to come up with a solution which bypassed this issue!

I ended up removing the Toolbar and FrameLayoutfrom HomeActivity, and instead created a new layout resource file and called it "app_bar.xml", which contained the following code:

<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <android.support.design.widget.CoordinatorLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        tools:context=".core.MainActivity">

        <FrameLayout
            android:id="@+id/mainContainer"
            android:layout_width="match_parent"
            android:layout_height="match_parent" />

    </android.support.design.widget.CoordinatorLayout>

    <android.support.design.widget.AppBarLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="@android:color/transparent"
        android:layout_alignParentStart="true"
        android:layout_alignParentTop="true"
        android:elevation="0dp"
        android:stateListAnimator="@null">

        <android.support.v7.widget.Toolbar
            android:id="@+id/toolbar"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"
            android:theme="@style/ThemeOverlay.AppCompat.Light"/>

    </android.support.design.widget.AppBarLayout>

</RelativeLayout>

I then followed by including the app_bar in the HomeActivity layout using the include tag (HomeActivity also houses the NavigationView nested within a DrawerLayout).

I hope this helps whomever comes across this question. If you have any further queries, ask away!