How to set a background for whole application in Android?

In my application I have a lot of layers and instead of setting开发者_如何转开发 a background image to each of them, I want to set a background once and for all. How can I do that?

Take a look at Apply a theme to an Activity or application to apply the background image across the whole application.

Add android:windowBackground to your theme:

<!-- Base application theme. -->
<style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
    <!-- Customize your theme here. -->
    <item name="colorPrimary">@color/colorPrimary</item>
    <item name="colorPrimaryDark">@color/colorPrimaryDark</item>
    <item name="colorAccent">@color/colorAccent</item>
    <item name="android:windowBackground">@color/colorPrimaryDark</item>
</style>

And of course make sure your manifest uses the theme for you application:

<?xml version="1.0" encoding="utf-8"?>
<manifest package="com.package.name"
          xmlns:android="http://schemas.android.com/apk/res/android">

    <application
        android:theme="@style/AppTheme">

        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN"/>
                <category android:name="android.intent.category.LAUNCHER"/>
            </intent-filter>
        </activity>

    </application>

</manifest>