Android TabHost如何实现顶部选项卡

用TabHost 来实现顶部选项卡,上代码:activity_main.xml <?xml version=1.0 encoding=utf-8?> <android.support.constraint.ConstraintLayout xmlns:android=http://schemas.android.com/apk/res/android xmlns:app=http://schemas.android.com/apk/res-auto xmlns:tools=http://schemas.android.com/tools android:lay