Home/ Questions/Q 6470033
In Process

The Archive Base Latest Questions

Editorial Team
  • 0
Asked: 2026-05-25T06:03:45+00:00

I’m reading Beginning Android Application Development by Wei-Mung Lee. I’m confused about custom actions

  • 0

I’m reading Beginning Android Application Development by Wei-Mung Lee. I’m confused about custom actions and categories.

Here’s some code from one example. The action is a package name. The only time that it’s ever referred to ever again is in 

Intent i = new Intent( "net.learn2develop.MyBrowser" );

to start an activity. How is it that this action, which is basically a package name, can know to start an activity? Just because it’s inside the activity tag?

The same thing with the category tag (different example):

<intent-filter>
   <action android:name=”android.intent.action.VIEW” />
   <action android:name=”net.learn2develop.MyBrowser” />
   <category android:name=”android.intent.category.DEFAULT” />
   <category android:name=”net.learn2develop.Apps” />
   <data android:scheme=”http” />
</intent-filter>

net.learn2develop.Apps is a name that was made up by the author. It really has no meaning, right? What purpose does it serve?

Share

Leave an answer

You must login to add an answer.

Need An Account,

1 Answer

  1. Editorial Team

    How is it that this action, which is basically a package name, can know to start an activity?

    Because the <intent-filter> of the activity advertised that it can be started via that action string. BTW, just because it’s written like a package name does not mean it has to be a package name (e.g., android.intent.action.VIEW is not a package). The package naming convention is to prevent accidental collisions with other installed apps.

    It really has no meaning, right?

    Well, it probably meant something to the author, though I couldn’t tell you what, exactly.

    What purpose does it serve?

    In normal Android development, you would not create a custom category. I cannot recall ever seeing one, and I’ve been doing Android development for quite a while now.

    Categories are usually used to distinguish different use cases. For example, perhaps the second-most-popular category besides DEFAULT is BROWSABLE. Activities supporting the VIEW action in the BROWSABLE category become eligible to be used from links in a Web browser. So, if I had an activity for VIEW/BROWSABLE and a MIME type of application/pdf, and the user clicked on a link to a PDF file in a browser, I could be chosen to view the PDF. However, if I lacked BROWSABLE as a category, then I would not be eligible for that link. Usually, an activity would only advertise BROWSABLE if it could retrieve an HTTP URL.

    Off the top of my head, I cannot think of a scenario where I’d use a custom category, though.

    • 0