android TV-Working with Channel Data

desaco發表於2016-01-22
Android

> Working with Channel Data

 Your TV input must provide Electronic Program Guide (EPG) data for at least one channel in its setup activity. You should also periodically update that data, with consideration for the size of the update and the processing thread that handles it. 

 In order for your TV input to work with EPG data, it must declare the read and write permissions in its Android manifest file as follows:

<uses-permission android:name="com.android.providers.tv.permission.READ_EPG_DATA" />
<uses-permission android:name="com.android.providers.tv.permission.WRITE_EPG_DATA" />
> The Android TV system database maintains records of channel data for TV inputs. In your setup activity, for each of your channels, you must map your channel data to the following fields of the TvContract.Channels class:

>Although the TV input framework is generic enough to handle both traditional broadcast and over-the-top (OTT) content without any distinction, you may want to define the following columns in addition to those above to better identify traditional broadcast channels:

 Pull your channel metadata (in XML, JSON, or whatever) from your backend server, and in your setup activity map the values to the system database as follows:

ContentValues values = new ContentValues();

values.put(Channels.COLUMN_DISPLAY_NUMBER, channel.mNumber);
values.put(Channels.COLUMN_DISPLAY_NAME, channel.mName);
values.put(Channels.COLUMN_ORIGINAL_NETWORK_ID, channel.mOriginalNetworkId);
values.put(Channels.COLUMN_TRANSPORT_STREAM_ID, channel.mTransportStreamId);
values.put(Channels.COLUMN_SERVICE_ID, channel.mServiceId);
values.put(Channels.COLUMN_VIDEO_FORMAT, channel.mVideoFormat);

Uri uri = context.getContentResolver().insert(TvContract.Channels.CONTENT_URI, values);
>  To make sure the channel and program information works with the system TV app's channel and program information presenter, follow the guidelines below.
  1. Channel number (COLUMN_DISPLAY_NUMBER)
  2. Icon (android:icon in the TV input's manifest)
  3. Program description (COLUMN_SHORT_DESCRIPTION)
  4. Program title (COLUMN_TITLE)
  5. Channel logo (TvContract.Channels.Logo)
    • Use the color #EEEEEE to match the surrounding text
    • Don't include padding
  6. Poster art (COLUMN_POSTER_ART_URI)
    • Aspect ratio between 16:9 and 4:3

 Note: Adding channel data to the ContentProvider can take time. Only add current programs (those within two hours of the current time) when you update, and use a Sync Adapter to update the rest of the channel data in the background. See the Android TV Live TV Sample App for an example.

> When updating the system database with a large amount of channel data, use the ContentResolverapplyBatch() or bulkInsert() method. Here's an example using applyBatch():

ArrayList<ContentProviderOperation> ops = new ArrayList<>();
int programsCount = mChannelInfo.mPrograms.size();
for (int j = 0; j < programsCount; ++j) {
    ProgramInfo program = mChannelInfo.mPrograms.get(j);
    ops.add(ContentProviderOperation.newInsert(
            TvContract.Programs.CONTENT_URI)
            .withValues(programs.get(j))
            .withValue(Programs.COLUMN_START_TIME_UTC_MILLIS,
                    programStartSec * 1000)
            .withValue(Programs.COLUMN_END_TIME_UTC_MILLIS,
                    (programStartSec + program.mDurationSec) * 1000)
            .build());
    programStartSec = programStartSec + program.mDurationSec;
    if (j % 100 == 99 || j == programsCount - 1) {
        try {
            getContentResolver().applyBatch(TvContract.AUTHORITY, ops);
        } catch (RemoteException | OperationApplicationException e) {
            Log.e(TAG, "Failed to insert programs.", e);
            return;
        }
        ops.clear();
    }
}

> Data manipulation, such as fetching a stream from the server or accessing the database, should not block the UI thread. Using an AsyncTask is one way to perform updates asynchronously.

private static class LoadTvInputTask extends AsyncTask<Uri, Void, Void>> {

    private Context mContext;

    public LoadTvInputTask(Context context) {
        mContext = context;
    }

    @Override
    protected Void doInBackground(Uri... uris) {
        try {
            fetchUri(uris[0]);
        } catch (IOException e) {
          Log.d(“LoadTvInputTask”, “fetchUri error”);
        }
        return null;
    }

    private void fetchUri(Uri videoUri) throws IOException {
        InputStream inputStream = null;
        try {
            inputStream = mContext.getContentResolver().openInputStream(videoUri);
            XmlPullParser parser = Xml.newPullParser();
            try {
                parser.setFeature(XmlPullParser.FEATURE_PROCESS_NAMESPACES, false);
                parser.setInput(inputStream, null);
                sTvInput = ChannelXMLParser.parseTvInput(parser);
                sSampleChannels = ChannelXMLParser.parseChannelXML(parser);
            } catch (XmlPullParserException e) {
                e.printStackTrace();
            }
        } finally {
            if (inputStream != null) {
                inputStream.close();
            }
        }
    }
}
 If you need to update EPG data on a regular basis, consider using a Sync Adapter or JobScheduler to run the update process during idle time, such as every day at 3:00 a.m.  Other techniques to separate the data update tasks from the UI thread include using the HandlerThread class, or you may implement your own using Looper and Handler classes.

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