安卓如何居中排名前actionBar的头衔？

<androidx.appcompat.widget.Toolbar
    android:id="@+id/toolbar"
    android:layout_width="match_parent"
    android:layout_height="?attr/actionBarSize"
    android:background="?attr/colorPrimary"
    android:title="@string/app_name"
    android:titleTextAppearance="@style/TextAppearance.Widget.AppCompat.Toolbar.Title"
    android:subtitleTextAppearance="@style/TextAppearance.Widget.AppCompat.Toolbar.Subtitle"
    app:titleTextColor="@color/colorTitle"
    app:titleMarginStart="16dp"
    app:titleMarginEnd="16dp"
    app:titleMarginTop="8dp"
    app:titleMarginBottom="8dp"
    app:contentInsetStartWithNavigation="0dp"
    app:contentInsetStart="0dp"
    app:contentInsetEnd="0dp"
    app:contentInsetRight="0dp"
    app:contentInsetLeft="0dp"
    app:contentInsetEndWithActions="0dp"
    app:titleTextAppearance="@style/TextAppearance.AppCompat.Widget.ActionBar.Title"
    app:titleMarginEnd="0dp"
    app:titleMarginStart="0dp"
    app:subtitleMarginStart="0dp"
    app:subtitleMarginEnd="0dp"
    app:layout_collapseMode="pin"
    app:popupTheme="@style/ThemeOverlay.AppCompat.Light"
    app:theme="@style/ToolbarTheme"
    app:layout_scrollFlags="scroll|enterAlways"
    android:gravity="center"
    >
</androidx.appcompat.widget.Toolbar>

Toolbar toolbar = findViewById(R.id.toolbar);
setSupportActionBar(toolbar);

getSupportActionBar().setTitle("居中头衔");