How Launcher decides which app icon to place in launcher?

Question

I have a very naive question. I've written a program which lists down all the installed applications in my Android OS [I've got total 339 in my case]. But in the Launcher [In my case TouchWiz Home] only 148 application Icons are shown.

My Question is: How does the launcher[TouchWiz Home] decide which app icon to show or not in Launcher?

Answer 1

Launcher will show those activities that have the following intent filters declared in the app's manifest file

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

Answer 2

When a developer publishes an app, he/she can decide if app has "launcher" icon(set a launcher intent in manifest file which is embedded in the APK).

Other apps maybe services or other kind of apps that has no launching behavior.