一个简单的网格布局
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:layout_width=m
