分类：AAndroid之旅

<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"     android:orientation="vertical" android:layout_width="match_parent"     android:layout_height="match_parent">     <TextView         android:id="@+id/tv_username"         android:layout_marginTop="20dp"         android:layout_width="wrap_cont…