[Sony Cross-Device Development Themes and Apps] Ticklefish:
This is your code:

<?xml version="1.0" encoding="utf-8"?>
<com.android.systemui.statusbar.phone.PhoneStatusBarView android:orientation="vertical" android:id="@id/status_bar" android:background="@drawable/system_bar_background" android:focusable="false" android:descendantFocusability="afterDescendants" android:layout_width="fill_parent" android:layout_height="@dimen/status_bar_height" android:accessibilityPaneTitle="@string/status_bar"
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:systemui="http://schemas.android.com/apk/res/com.android.systemui">
<FrameLayout android:id="@id/background" android:layout_width="fill_parent" android:layout_height="fill_parent" />
<LinearLayout android:gravity="center" android:layout_gravity="center" android:orientation="horizontal" android:id="@id/middle_clock_container" android:layout_width="wrap_content" android:layout_height="fill_parent" />
<FrameLayout android:id="@id/status_bar_area" android:layout_width="fill_parent" android:layout_height="fill_parent">
[COLOR="Red"]<TextView android:textSize="14.0dip" android:textColor="#ffffffff" android:gravity="left|center" android:layout_width="wrap_content" android:layout_height="fill_parent" android:text="@string/hello" android:singleLine="true" />[/COLOR]
<ImageView android:id="@id/notification_lights_out" android:paddingBottom="2.0dip" android:visibility="gone" android:layout_width="@dimen/status_bar_icon_size" android:layout_height="fill_parent" android:src="@drawable/ic_sysbar_lights_out_dot_small" android:scaleType="center" android:paddingStart="@dimen/status_bar_padding_start" />
<LinearLayout android:orientation="horizontal" android:id="@id/status_bar_contents" android:layout_width="fill_parent" android:layout_height="fill_parent" android:paddingStart="@dimen/status_bar_padding_start" android:paddingEnd="@dimen/status_bar_padding_end">
<ViewStub android:id="@id/operator_name" android:layout="@layout/operator_name" android:layout_width="wrap_content" android:layout_height="fill_parent" />
<FrameLayout android:layout_width="0.0dip" android:layout_height="fill_parent" android:layout_weight="1.0">
<include layout="@layout/heads_up_status_bar_layout" />
<LinearLayout android:id="@id/status_bar_left_side" android:clipChildren="false" android:layout_width="fill_parent" android:layout_height="fill_parent">
<LinearLayout android:gravity="center_vertical" android:orientation="horizontal" android:id="@id/left_clock_container" android:layout_width="wrap_content" android:layout_height="fill_parent">
<LinearLayout android:gravity="center" android:orientation="horizontal" android:id="@id/network_logo_image_container" android:layout_width="wrap_content" android:layout_height="fill_parent" />
<include android:layout_width="wrap_content" android:layout_height="fill_parent" layout="@layout/qs_status_bar_clock" />
</LinearLayout>
<com.android.systemui.statusbar.AlphaOptimizedFrameLayout android:orientation="horizontal" android:id="@id/notification_icon_area" android:clipChildren="false" android:layout_width="0.0dip" android:layout_height="fill_parent" android:layout_weight="1.0" />
</LinearLayout>
</FrameLayout>
<android.widget.Space android:gravity="center" android:id="@id/cutout_space_view" android:layout_width="0.0dip" android:layout_height="fill_parent" />
<com.android.keyguard.AlphaOptimizedLinearLayout android:gravity="end|center" android:orientation="horizontal" android:id="@id/system_icon_area" android:layout_width="wrap_content" android:layout_height="fill_parent">
<ViewStub android:id="@id/qs_knox_custom_statusbar_viewstub" android:layout="@layout/qs_knox_custom_statusbar_text" android:layout_width="wrap_content" android:layout_height="fill_parent" />
<include layout="@layout/system_icons" />
<LinearLayout android:gravity="center" android:orientation="horizontal" android:id="@id/right_clock_container" android:layout_width="wrap_content" android:layout_height="fill_parent" />
</com.android.keyguard.AlphaOptimizedLinearLayout>
</LinearLayout>
<ViewStub android:id="@id/emergency_cryptkeeper_text" android:layout="@layout/emergency_cryptkeeper_text" android:layout_width="wrap_content" android:layout_height="fill_parent" />
</FrameLayout>
</com.android.systemui.statusbar.phone.PhoneStatusBarView>

I've added some CODE tags, highlighted the line you want to center, and I've done my best to remove those smilies. It makes the code a lot more readable.

You can center your text in the Layout it's in but that won't help you any. Currently it's inside the "@id/status_bar_area" FrameLayout, which displays everything on the left side of the status bar. You need the text centered in the "@id/background" FrameLayout, which displays the entire status bar.

The easiest way to do this is to move your text line to inside that Layout and add an attribute to center it:

<?xml version="1.0" encoding="utf-8"?>
<com.android.systemui.statusbar.phone.PhoneStatusBarView android:orientation="vertical" android:id="@id/status_bar" android:background="@drawable/system_bar_background" android:focusable="false" android:descendantFocusability="afterDescendants" android:layout_width="fill_parent" android:layout_height="@dimen/status_bar_height" android:accessibilityPaneTitle="@string/status_bar"
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:systemui="http://schemas.android.com/apk/res/com.android.systemui">
<FrameLayout android:id="@id/background" android:layout_width="fill_parent" android:layout_height="fill_parent" />
<TextView android:textSize="14.0dip" android:textColor="#ffffffff" [color="red"]android:layout_gravity="center"[/color] android:gravity="center" android:layout_width="wrap_content" android:layout_height="fill_parent" android:text="@string/hello" android:singleLine="true" />
<LinearLayout android:gravity="center" android:layout_gravity="center" android:orientation="horizontal" android:id="@id/middle_clock_container" android:layout_width="wrap_content" android:layout_height="fill_parent" />
<FrameLayout android:id="@id/status_bar_area" android:layout_width="fill_parent" android:layout_height="fill_parent">
....
....

This is a bit of a cheat as this won't stop icons from overlapping the text though. If you find that's a problem, we should be able to fix it but that's going to involve a bit more thinking as we'll need to start messing about with layout_weights..