Android puts the button under the transparent layout file

In XML, the order in which labels are arranged from top to bottom determines the sequence in the upper and lower layers on the phone screen.

such as: <relativelayout xmlns:android= "Http://schemas.android.com/apk/res/android"
Xmlns:tools= "Http://schemas.android.com/tools"
Android:layout_width= "Match_parent"
android:layout_height= "Match_parent"

<!--grey and transparent linearlayout-->

<linearlayout
Android:layout_width= "Match_parent"
android:layout_height= "Match_parent"
android:background= "#55CDCDC1" >

</LinearLayout>

<button
Android:layout_width= "50DP"
android:layout_height= "50DP"/>

</RelativeLayout>

If this is the case, the button is on the gray transparent LinearLayout,

If the button and LinearLayout are swapped, the buttons are below the gray transparent LinearLayout

Android puts the button under the transparent layout file