默认布局

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.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="match_parent"
    android:layout_height="match_parent"



    tools:context=".MainActivity2">


    <ListView
        android:id="@+id/device_list"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:divider="@color/teal_700"
        android:dividerHeight="1px"
        tools:layout_editor_absoluteX="16dp"
        tools:layout_editor_absoluteY="16dp" >



    </ListView>


</androidx.constraintlayout.widget.ConstraintLayout>