Layout below not working in android relative xml

Question

I'm confused why android:layout_below is not working, I just need to put the button below the border line and I don't wanna use android:layout_marginTop="570dp because the android phone has different sizes, Is somebody know how can I arrange the layout of this? it helps me a lot thanks in advance.

This is what I want to achieve

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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"
    android:orientation="vertical"
    tools:context=".MainActivity">

    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_alignParentLeft="true"
        android:layout_alignParentTop="true"
        android:layout_marginLeft="10dp"
        android:layout_marginTop="15dp"
        android:layout_marginRight="10dp"
        android:layout_marginBottom="100dp"
        android:background="@drawable/selector_fieldset_background"
        android:orientation="vertical"
        android:id="@+id/linearl">

    </RelativeLayout>
    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true"
        android:background="@color/white"
        android:paddingLeft="20dp"
        android:paddingRight="20dp"
        android:text="Cash Card Scanner"
        android:textSize="15dp"
        android:textAppearance="?android:attr/textAppearanceLarge"/>

        <Button
            android:id="@+id/button2"
            android:layout_centerInParent="true"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="SCAN"
            android:layout_below="@+id/linearl"
          
            />
</RelativeLayout>

Drawable selector_fieldset_background.xml

<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle" >
<solid android:color="#FFFFFF" />
<stroke
    android:width="2dip"
    android:color="#25000000" />
</shape>

Answer 1

Just try this, works for me:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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"
    android:orientation="vertical"
    tools:context=".MainActivity">

    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_alignParentTop="true"
        android:layout_marginLeft="10dp"
        android:layout_marginTop="15dp"
        android:layout_marginRight="10dp"
        android:layout_marginBottom="10dp"
        android:background="@drawable/selector_fieldset_background"
        android:orientation="vertical"
        android:id="@+id/linearl"
        android:layout_above="@+id/button2"
        >

    </RelativeLayout>
    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true"
        android:background="@color/white"
        android:paddingLeft="20dp"
        android:paddingRight="20dp"
        android:text="Cash Card Scanner"
        android:textSize="15dp"
        android:textAppearance="?android:attr/textAppearanceLarge"/>

    <Button
        android:id="@+id/button2"
        android:layout_centerInParent="true"
        android:layout_width="match_parent"
        android:layout_height="90dp"
        android:text="SCAN"
        android:layout_alignParentBottom="true"
        />
</RelativeLayout>