Question

The <application> tag for the Android Manifest contains a logo attribute which I have never seen before. What is the difference between your application’s icon and its logo? Is it used purely for market?

Answer 1

The ActionBar will use the android:logo attribute of your manifest, if
one is provided. That lets you use separate drawable resources for the
icon (Launcher) and the logo (ActionBar, among other things).

Source: Android: How to change the ActionBar "Home" Icon to be something other than the app icon?

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setDisplayUseLogoEnabled()
Enables the use of an alternative image (a “logo”) in the Action
Bar, instead of the default application icon. A logo is often a wider,
more detailed image that represents the application. When this is
enabled, the system uses the logo image defined for the application
(or the individual activity) in the manifest file, with the
android:logo attribute. The logo will be resized as necessary to fit
the height of the Action Bar. (Best practice is to design the logo at
the same size as your application icon.)

Source: http://developer.android.com/guide/topics/ui/actionbar.html#Style

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To replace the icon with a logo, specify your application logo in the
manifest file with the android:logo attribute, then call
setDisplayUseLogoEnabled(true) in your activity.

Source: http://developer.android.com/sdk/android-3.0.html#api