Align button at the bottom 1/3 of the screen

Question

I'm trying to align a button not right at the bottom of the screen but at a slight distance above the bottom line. How can I do that? I've tried centering the button vertically and horizontally and it works, but I need to either move the button a little below the center or a little above the bottom line.

I need to move the "PLAY" button a little lower on the screen. Additionally, I also need to scale the button down a bit, to like 80% of its current size. How can I do that?

<?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:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="acevix.gladiators3.MainActivity">

<ImageView
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    app:srcCompat="@drawable/splash"
    android:id="@+id/imageView"
    android:scaleType="centerCrop"
    android:layout_alignParentBottom="true"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true"
    android:adjustViewBounds="true" />

<Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_centerHorizontal="true"
    android:layout_centerVertical="true"
    android:layout_marginBottom="50dp"
    android:id="@+id/button3"
    android:background="@drawable/play" />

</RelativeLayout>

Answer 1

Use this codes,

android:layout_alignParentBottom="true"
android:layout_centerHorizontal="true"
android:layout_marginBottom="30dp"

Try this;

<RelativeLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" 
        android:layout_alignParentBottom="true"
        android:layout_centerHorizontal="true"
        android:layout_marginBottom="30dp"/>

</RelativeLayout>

Update Code

Use this : android:layout_below

<RelativeLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <ImageView
        android:id="@+id/logo"
        android:layout_width="200dp"
        android:layout_height="80dp"
        android:layout_centerInParent="true" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@id/logo"
        android:layout_centerInParent="true"
        android:layout_marginTop="30dp" />

</RelativeLayout>

Answer 2

For different screen resolutions you can use intuit/sdp

add this line to your gradle file

compile 'com.intuit.sdp:sdp-android:1.0.3'