android TV-Building TV Channels，Developing a TV Input Service

》Building TV Channels

 To provide your users a similar experience, use the TV Input Framework to create channels for publishing video or music content so that your media appears alongside traditional TV channels in the programming guide.

 Android supports receiving and playback of live video content through the TV Input Framework in Android 5.0 (API level 21). This framework provides a unified method for receiving audio and video channel content from hardware sources, such as HDMI ports and built-in-tuners, and software sources, such as video streamed over the internet.The framework enables developers to define live TV input sources by implementing a TV input service. 

 The TV Input Framework is designed to provide access to a wide variety of live TV input sources and bring them together in a single user interface for users to browse, view, and enjoy content. Building a TV input service for your content can help make it more accessible on TV devices.

》Developing a TV Input Service

 With the TV input service, you can provide parental controls, program guide information, and content ratings.

 > To develop a TV input service, you implement the following components:

• TvInputService provides long-running and background availability for the TV input
• TvInputService.Session maintains the TV input state and communicates with the hosting app
• TvContract describes the channels and programs available to the TV input
• TvContract.Channels represents information about a TV channel
• TvContract.Programs describes a TV program with data such as program title and start time
• TvTrackInfo represents an audio, video, or subtitle track
• TvContentRating describes a content rating, allows for custom content rating schemes
• TvInputManager provides an API to the system TV app and manages the interaction with TV inputs and apps

 >Your app manifest must declare your TvInputService. Within that declaration, specify the BIND_TV_INPUTpermission to allow the service to connect the TV input to the system. A system service (TvInputManagerService) performs the binding and has that permission. The system TV app sends requests to TV input services via the TvInputManager interface. The service declaration must also include an intent filter that specifies the TvInputService as the action to perform with the intent. Also within the service declaration, declare the service meta data in a separate XML resource. 

<service android:name="com.example.sampletvinput.SampleTvInput"
    android:label="@string/sample_tv_input_label"
    android:permission="android.permission.BIND_TV_INPUT">
    <intent-filter>
        <action android:name="android.media.tv.TvInputService" />
    </intent-filter>
    <meta-data android:name="android.media.tv.input"
      android:resource="@xml/sample_tv_input" />
</service>

<tv-input xmlns:android="http://schemas.android.com/apk/res/android"
  android:setupActivity="com.example.sampletvinput.SampleTvInputSetupActivity" />

>the onCreate() method initializes theCaptioningManager and prepares to handle theACTION_BLOCKED_RATINGS_CHANGED andACTION_PARENTAL_CONTROLS_ENABLED_CHANGED actions. These actions describe system intents fired when the user changes the parental control settings, and when there is a change on the list of blocked ratings.

@Override
public void onCreate() {
    super.onCreate();
    mHandlerThread = new HandlerThread(getClass()
      .getSimpleName());
    mHandlerThread.start();
    mDbHandler = new Handler(mHandlerThread.getLooper());
    mHandler = new Handler();
    mCaptioningManager = (CaptioningManager)
      getSystemService(Context.CAPTIONING_SERVICE);

    setTheme(android.R.style.Theme_Holo_Light_NoActionBar);

    mSessions = new ArrayList<BaseTvInputSessionImpl>();
    IntentFilter intentFilter = new IntentFilter();
    intentFilter.addAction(TvInputManager
      .ACTION_BLOCKED_RATINGS_CHANGED);
    intentFilter.addAction(TvInputManager
      .ACTION_PARENTAL_CONTROLS_ENABLED_CHANGED);
    registerReceiver(mBroadcastReceiver, intentFilter);
}

> The TvInputService creates a TvInputService.Session that implements Handler.Callback to handle player state changes. With onSetSurface(), the TvInputService.Session sets the Surface with the video content.

 The TvInputService.Session handles the onTune() event when the user selects a channel, and notifies the system TV app for changes in the content and content meta data. These notify() methods are described inControl Content and Handle Track Selection further in this training.

 The system TV app works with the setup activity you define for your TV input. The setup activity is required and must provide at least one channel record for the system database. The system TV app will invoke the setup activity when it cannot find a channel for the TV input.