Background in Android Studio doesn't work

Question

I'm trying to setup an image as background of my app. I see it in Android Studio preview but if I load the app on my phone (Android 5) I can't see the image. This is the code. I'm new in Android world.

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout 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:fitsSystemWindows="true"
    tools:context="lorenzobenevento.mydomotics.MainActivity"
    android:background="@drawable/background">

    <android.support.design.widget.AppBarLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:theme="@style/AppTheme.AppBarOverlay">

        <android.support.v7.widget.Toolbar
            android:id="@+id/toolbar"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"
            app:popupTheme="@style/AppTheme.PopupOverlay" />

    </android.support.design.widget.AppBarLayout>

    <include layout="@layout/content_main" />

</android.support.design.widget.CoordinatorLayout>

Thanks in advance and sorry for my bad English.

Answer 1

The coordinator layout is like a framelayout. Everything you put inside will be in front of what ever widgets and such are defined before it.

Importantly for you that means everything in the xml file:

<include layout="@layout/content_main" />

will be in front of the background image you've defined in the coordinator layout. Chances are the content in there is covering up, so consider setting the background image in that xml file instead.