Question

How to add a background theme and/or background wallpaper to my app? Right now my app background is plane.

Answer 1

Create an XML file in the values directory that contains the style. It could be something like:

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <style name="YourTheme" parent="@android:style/Theme">
        <item name="android:windowBackground">@drawable/your_background</item>
    </style>
</resources>

For the case above to work, you need to have an image called your_background.png in the drawable folder. Then, you can apply that style to either your whole app or one specific activity by doing this in your manifest file:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
      package="bla.bla">
    <application android:theme="@style/YourTheme"> <!-- This is for the whole app  -->

        <activity android:name="bla.bla.YourActivity"
                  android:theme="@style/SplashTheme"/><!-- This is for a specific activity  -->

    </application>
</manifest>