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