LinearLayout 组件居中显示

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="wrap_content"    android:layout_height="wrap_content"    android:background="@drawable/bg_`xx`"    android:gravity="center_horizontal|center_vertical"    android:orientation="vertical" >    <TextView        android:id="@+id/tv"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:gravity="center"        android:text=""        android:textColor="@color/whilte"        android:textSize="16sp" /></LinearLayout>