LauncherActivity usage

Question

Could you please explain me purpose and usage of LauncherActivity? Documentation says that it "Displays a list of all activities which can be performed for a given intent". I understood that it should automatically build list of all activities found in application and provide their launching. Am I right?

And how to use it? I have found no examples in the web.

Answer 1

Google Code shows the class code itself... It has a different constructor than is described in the Android Platform API.

public abstract class LauncherActivity extends ListActivity {
   Intent mIntent;
   PackageManager mPackageManager;
   IconResizer mIconResizer;

Your phone can have more than one possible app which handles a given intent. One great example is opening a webpage. There's the stock WebKit based browser, you can install Firefox Mobile, Dolphin Browser, Opera Mini... When they all advertise that they can handle a given intent, how does the device know which one it should pass the intent to?

Android will use a LauncherActivity to bring up a selection list of packages where each one listed is one that knows how to do something with the given intent you provide it. When you pick one, you're picking which app you want, and the intent is routed to the matching app.

From that perspective, it's a class that's really part of the Android OS support code, part of figuring out where to distribute given intents to. It's hard to see a situation where you would need to involve yourself with it directly... you should be able to just call StartActivity(Intent), which throws the intent over the wall to the OS, and at that point the device itself should fire up LauncherActivity on its own (if it's even needed).

Completely unrelated (and horribly name-disambiguated) is your application's "Launcher Activity" (documentation) -- an activity that shows in AndroidManifest.xml with an intent filter with "android.intent.action.MAIN" and "android.intent.category.LAUNCHER" ... This is how your app advertises to the system that it wants to have an icon in the device's application list, and that a specific activity should be started when that icon's clicked. You absolutely need to do that.