Android tutorial 5: A Complete media player
This tutorial wants to be the “demo application” that showcases what can be done with GStreamer in the Android platform.
It is intended to be downloaded in final, compiled, form rather than analyzed for its pedagogical value, since it adds very little GStreamer knowledge over what has already been shown in Android tutorial 4: A basic media player.
FIXME: Do we want to provide a binary of the app?
The previous tutorial already implemented a basic media player. This one simply adds a few finishing touches. In particular, it adds the capability to choose the media to play, and disables the screensaver during media playback.
These are not features directly related to GStreamer, and are therefore outside the scope of these tutorials. Only a few implementation pointers are given here.
Registering as a media player
AndroidManifest.xml tells the Android system the capabilities of
the application. By specifying in the
intent-filter of the activity
that it understands the
image/* MIME types,
the tutorial will be offered as an option whenever an application
requires such medias to be viewed.
“Unfortunately”, GStreamer knows more file formats than Android does,
so, for some files, Android will not provide a MIME type. For these
cases, a new
intent-filter has to be provided which ignores MIME types
and focuses only in the filename extension. This is inconvenient because
the list of extensions can be large, but there does not seem to be
another option. In this tutorial, only a very short list of extensions
is provided, for simplicity.
Finally, GStreamer can also playback remote files, so URI schemes like
http are supported in another
intent-filter. Android does not
provide MIME types for remote files, so the filename extension list has
to be provided again.
Once we have informed the system of our capabilities, it will start
to invoke our activity, which will contain the desired URI to play. In
onCreate() method the intent that invoked the activity is
retrieved and checked for such URI.
Implementing a file chooser dialog
The UI includes a new button ![media-next) which was not present in Android tutorial 4: A basic media player. It invokes a file chooser dialog (based on the Android File Dialog project) that allows you to choose a local media file, no matter what extension or MIME type it has.
If a new media is selected, it is passed onto the native code (which
will set the pipeline to READY, pass the URI onto
playbin, and bring
the pipeline back to the previous state). The current position is also
reset, so the new clip does not start in the previous position.
Preventing the screen from turning off
While watching a movie, there is typically no user activity. After a short period of such inactivity, Android will dim the screen, and then turn it off completely. To prevent this, a Wake Lock is used. The application acquires the lock when the Play button is pressed, so the screen is never turned off, and releases it when the Pause button is pressed.
This finishes the series of Android tutorials. Each one of the preceding tutorials has evolved on top of the previous one, showing how to implement a particular set of features, and concluding in this tutorial 5. The goal of tutorial 5 is to build a complete media player which can already be used to showcase the integration of GStreamer and Android.
It has been a pleasure having you here, and see you soon!
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