Android - Center TextView Horizontally in LinearLayout

What's happening is that since the the TextView is filling the whole width of the inner LinearLayout it is already in the horizontal center of the layout. When you use android:layout_gravity it places the widget, as a whole, in the gravity specified. Instead of placing the whole widget center what you're really trying to do is place the content in the center which can be accomplished with android:gravity="center_horizontal" and the android:layout_gravity attribute can be removed.

If you set <TextView> in center in <Linearlayout> then first put android:layout_width="fill_parent" compulsory
No need of using any other gravity

    <LinearLayout
            android:layout_toRightOf="@+id/linear_profile" 
            android:layout_height="wrap_content"
            android:layout_width="fill_parent"
            android:orientation="vertical"
            android:gravity="center_horizontal">
            <TextView 
                android:layout_height="wrap_content"
                android:layout_width="wrap_content"
                android:text="It's.hhhhhhhh...."
                android:textColor="@color/Black"

                />
    </LinearLayout>

Use android:gravity="center" in TextView instead of layout_gravity.

<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent">

<LinearLayout
android:orientation="horizontal"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:background="@drawable/title_bar_background">

<TextView
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:gravity="center"
    android:textAppearance="?android:attr/textAppearanceLarge"
    android:padding="10dp"
    android:text="HELLO WORLD" />

</LinearLayout>