docs: Adding Android TV App Link docs

    <li><a href="#permission">Get Permission</a></li>

    <li><a href="#register">Register Channels in the Database</a></li>

    <li><a href="#update">Update Channel Data</a></li>

    <li><a href="#applink">Add App Link Information</a></li>

  </ol>

  <h2>Try It Out</h2>

  <ul>

</div>

</div>

<p>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. This lesson discusses creating and updating

channel and program data on the system database with these considerations in mind.</p>

<p>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. Additionally, you can provide app links for channels

that guide the user to related content and activities.

This lesson discusses creating and updating channel and program data on the

system database with these considerations in mind.</p>

<p>&nbsp;</p>

  ID</li>

</ul>

<p>If you want to provide app link details for your channels, you need to

update some additional fields. For more information on app link fields, see

<a href="#applink">Add App Link Information</a>.

<p>For internet streaming based TV inputs, assign your own values to the above accordingly so that

each channel can be identified uniquely.</p>

{@link android.os.HandlerThread} class, or you may implement your own using {@link android.os.Looper}

and {@link android.os.Handler} classes.  See <a href="{@docRoot}guide/components/processes-and-threads.html">

Processes and Threads</a> for more information.</p>

<h2 id="applink">Add App Link Information</h2>

<p>Channels can use <em>app links</em> to let users easily launch a related

activity while they are watching channel content. Channel apps use

app links to extend user engagement by launching activities that show

related information or additional content. For example, you can use app links

to do the following:</p>

<ul>

<li>Guide the user to discover and purchase related content.</li>

<li>Provide additional information about currently playing content.</li>

<li>While viewing episodic content, start viewing the next episode in a

series.</li>

<li>Let the user interact with content&mdash;for example, rate or review

content&mdash;without interrupting content playback.</li>

</ul>

<p>App links are displayed when the user presses <b>Select</b> to show the

TV menu while watching channel content.</p>

<img alt="" src="{@docRoot}images/training/tv/tif/app-link.png"

srcset="{@docRoot}images/training/tv/tif/app-link.png 1x,

{@docRoot}images/training/tv/tif/app-link-2x.png 2x" id="figure1"/>

<p class="img-caption"><strong>Figure 1.</strong> An example app link

displayed on the <b>Channels</b> row while channel content is shown.</p>

<p>When the user selects the app link, the system starts an activity using

an intent URI specified by the channel app. Channel content continues to play

while the app link activity is active. The user can return to the channel

content by pressing <b>Back</b>.</p>

<h3 id="card">Provide App Link Channel Data</h4>

<p>Android TV automatically creates an app link for each channel,

using information from the channel data. To provide app link information,

specify the following details in your

{@link android.media.tv.TvContract.Channels} fields:

</p>

<ul>

<li>{@link android.media.tv.TvContract.Channels#COLUMN_APP_LINK_COLOR} - The

accent color of the app link for this channel. For an example accent color,

see figure 2, callout 3.

</li>

<li>{@link android.media.tv.TvContract.Channels#COLUMN_APP_LINK_ICON_URI} -

The URI for the app badge icon of the app link for this channel. For an

example app badge icon, see figure 2, callout 2.

</li>

<li>{@link android.media.tv.TvContract.Channels#COLUMN_APP_LINK_INTENT_URI} -

The intent URI of the app link for this channel. You can create the URI

using {@link android.content.Intent#toUri(int) toUri(int)} with

{@link android.content.Intent#URI_INTENT_SCHEME URI_INTENT_SCHEME} and

convert the URI back to the original intent with

{@link android.content.Intent#parseUri parseUri()}.

</li>

<li>{@link android.media.tv.TvContract.Channels#COLUMN_APP_LINK_POSTER_ART_URI}

- The URI for the poster art used as the background of the app link

for this channel. For an example poster image, see figure 2, callout 1.</li>

<li>{@link android.media.tv.TvContract.Channels#COLUMN_APP_LINK_TEXT} -

The descriptive link text of the app link for this channel. For an example

app link description, see the text in figure 2, callout 3.</li>

</ul>

<img alt="" src="{@docRoot}images/training/tv/tif/app-link-diagram.png"/>

<p class="img-caption"><strong>Figure 2.</strong> App link details.</p>

<p>If the channel data doesn't specify app link information, the system

creates a default app link. The system chooses default details as follows:</p>

<ul>

<li>For the intent URI

({@link android.media.tv.TvContract.Channels#COLUMN_APP_LINK_INTENT_URI}),

the system uses the {@link android.content.Intent#ACTION_MAIN ACTION_MAIN}

activity for the {@link android.content.Intent#CATEGORY_LEANBACK_LAUNCHER

CATEGORY_LEANBACK_LAUNCHER} category, typically defined in the app manifest.

If this activity is not defined, a non-functioning app link appears—if

the user clicks it, nothing happens.</li>

<li>For the descriptive text

({@link android.media.tv.TvContract.Channels#COLUMN_APP_LINK_TEXT}), the system

uses "Open <var>app-name</var>". If no viable app link intent URI is defined,

the system uses "No link available".</li>

<li>For the accent color

({@link android.media.tv.TvContract.Channels#COLUMN_APP_LINK_COLOR}),

the system uses the default app color.</li>

<li>For the poster image

({@link android.media.tv.TvContract.Channels#COLUMN_APP_LINK_POSTER_ART_URI}),

the system uses the app's home screen banner. If the app doesn't provide a

banner, the system uses a default TV app image.</li>

<li>For the badge icon

({@link android.media.tv.TvContract.Channels#COLUMN_APP_LINK_ICON_URI}), the

system uses a badge that shows the app name. If the system is also using the

app banner or default app image for the poster image, no app badge is shown.

</li>

</ul>

<p>You specify app link details for your channels in your app's

setup activity. You can update these app link details at any point, so

if an app link needs to match channel changes, update app

link details and call

{@link android.content.ContentResolver#update(android.net.Uri,

android.content.ContentValues, java.lang.String, java.lang.String[])

ContentResolver.update()} as needed. For more details on updating

channel data, see <a href="#update">Update Channel Data</a>.

</p>