Providing Messaging for Auto

Video

DevBytes: Android Auto Messaging

Staying connected through text messages is important to many drivers. Chat apps can let users know if a child need to be picked up, or if a dinner location has been changed. Apps that provide sports information might tell the user who just won the big game, and let the user ask questions about other games being played. The Android framework enables messaging apps to extend their services into car dashboards using a standard user interface that lets drivers keep their eyes on the road.

Apps that support messaging can be extended to pass messaging notifications to Auto dashboard systems, alerting them to new messages and allowing them to respond. You can configure your messaging app to provide these services when an Android mobile device with your app installed is connected to an Auto dashboard. Once connected, your app can provide text information to users and allow them to respond. The Auto dashboard system handles displaying the notification and the interface for replies.

This lesson assumes that you have built an app that displays messages to the user and receive the user's replies, such as a chat app. It shows you how to extend your app to hand those messages off to an Auto device for display and replies.

Provide Messaging Services

Messaging apps do not run directly on the Android dashboard hardware. They are installed on separate, Android mobile device. When the mobile device is plugged into a dashboard, the installed messaging apps can offer services for viewing and responding to messages through the Auto user interface.

To enable your app to provide messaging services for Auto devices:

  • Configure your app manifest to indicate that your app provides messaging services which are compatible with Android Auto dashboard devices.
  • Build and send a specific type of notification for display on Auto devices.
  • Configure your app to receive Intent objects that indicate a user has read or replied to a message.

Configure Your Manifest

You configure your app manifest to indicate that it supports messaging services for Auto devices and handle message actions. This section describes what changes to make to your manifest to support messaging for Auto devices.

Declare Auto messaging support

When a user connects a Android mobile device to a dashboard running Android, the dashboard device looks for apps that declare support for vehicle services, such as messaging. You indicate that your app supports cars capabilities using the following manifest entry: 

<application>
    ...
    <meta-data android:name="com.google.android.gms.car.application"
        android:resource="@xml/automotive_app_desc" />
    ...
<application>

This manifest entry refers to a secondary xml file, where you declare what Auto capabilities your app supports. For an app that supports messaging for Auto devices, add an xml file to the res/xml/ your app's development project directory as automotive_app_desc.xml, with the following content: 

<automotiveApp>
    <uses name="notification"/>
</automotiveApp>

For more information about declaring capabilities for Auto devices, see Getting Started with Auto.

Define read and reply intent filters

Auto devices use Intent objects that indicate a user has read or replied to a message provided by your app. Your app defines intent types for reading and replying to messages and adds this information to messaging notifications for Auto devices, so that the dashboard system can notify your app when a user takes one of these actions.

You define the read action and reply action intents types for your app and the BroadcastReceiver classes that handle them in the manifest. The following code example demonstrates how to declare these intents and their associated receivers. 

<application>
    ...
    <receiver android:name=".MyMessageReadReceiver">
        <intent-filter>
          <action android:name="com.myapp.messagingservice.ACTION_MESSAGE_HEARD"/>
        </intent-filter>
    </receiver>

    <receiver android:name=".MyMessageReplyReceiver">
        <intent-filter>
          <action android:name="com.myapp.messagingservice.ACTION_MESSAGE_REPLY"/>
        </intent-filter>
    </receiver>
    ...
</application>

The definition of the BroadcastReceiver classes shown in this example is discussed in Handle User Actions.

Import Support Library for Messaging

Building notifications for use with Auto devices requires classes from the v4 support library. Use the Android SDK Manager to update the Extras > Android Support Repository to version 9 or higher and the Extras > Android Support Library to version 21.0.2 or higher.

After you have updated the support libraries, import them into your Android Studio development project by adding this dependency to your build.gradle file: 

dependencies {
    ...
    compile 'com.android.support:support-v4:21.0.+'
}

For information about importing the support library into development projects for other development environments, see Support Library Setup.

Notify Users of Messages

A messaging app provides messages to a connected Auto dashboard using the notifications framework. When your messaging app has a message for a user, you build a specially configured notification that is received by the dashboard system and presented to the user. The Auto device manages the presentation on the dashboard screen and may play the message via text-to-speech. The dashboard system also handles voice interaction if the user replies to a message using verbal input.

The messaging user interface for Auto presents users with two levels of information about messages. The first level of notification tells users what conversations are available, and who they are with, but not the content of the messages. Typically, a conversation is one or more messages from another user to the Auto user.

The second level of the notification is the actual content of messages in the conversation. If a user indicates they want to hear the messages in a conversation, the Auto user interface plays the messages using text-to-speech.

This section describes how to notify Auto users that conversations are available and provide the content of messages in those conversations.

Build message conversations

Messaging notifications for Auto organize messages into conversations using the NotificationCompat.CarExtender.UnreadConversation class, that represents an unread or new portion of a conversation from a particular sender. It contains a list of messages from the sender.

Use the NotificationCompat.CarExtender.UnreadConversation.Builder class to create an unread conversation object, as shown in the following example code: 

// Build a RemoteInput for receiving voice input in a Car Notification
RemoteInput remoteInput = new RemoteInput.Builder(EXTRA_VOICE_REPLY)
        .setLabel(getApplicationContext().getString(R.string.notification_reply))
        .build();

// Create an unread conversation object to organize a group of messages
// from a particular sender.
UnreadConversation.Builder unreadConvBuilder =
    new UnreadConversation.Builder(participantName)
        .setReadPendingIntent(msgHeardPendingIntent)
        .setReplyAction(replyPendingIntent, remoteInput);

This conversation object includes a PendingIntent, which allows the Auto device to signal your app that the conversation has been read by the Auto user. The construction of this intent is discussed in the Creating conversation read and reply intents section.

If your app supports replying to a conversation, you must call the setReplyAction() method and provide a pending intent to pass that user action back to your app. The NotificationCompat.CarExtender.UnreadConversation object you create must also include a RemoteInput object. When the Auto user receiving this conversation speaks a reply, the remote input objects lets your app get a text version of the voice reply.

Associate messages with conversations

Messages provided for Auto must be associated with a conversation using the NotificationCompat.CarExtender.UnreadConversation class. The following code example shows how to associate individual messages with a conversation object. 

// Note: Add messages from oldest to newest to the UnreadConversation.Builder
for (Iterator<String> messages = conversation.getMessages().iterator();
     messages.hasNext(); ) {
    String message = messages.next();
    unreadConvBuilder.addMessage(message);
}

When a new message arrives in a particular conversation, your app should check if there is already a conversation object for that particular conversation. If there is, associate the new message with the existing conversation instead of building a new one.

Create conversation read and reply intents

Unread conversation objects contain intents for reading and replying to a conversation. You create a PendingIntent object for each of these actions, so the Auto device can notify your app of action taken by the Auto user on a particular conversation.

The following example code demonstrates how to define a PendingIntent to let your app know if a conversation was listened to by the Auto user: 

Intent msgHeardIntent = new Intent()
    .addFlags(Intent.FLAG_INCLUDE_STOPPED_PACKAGES)
    .setAction(com.myapp.messagingservice.ACTION_MESSAGE_HEARD)
    .putExtra("conversation_id", conversationId);

PendingIntent msgHeardPendingIntent =
    PendingIntent.getBroadcast(getApplicationContext(),
        conversationId,
        msgHeardIntent,
        PendingIntent.FLAG_UPDATE_CURRENT);

In this example, conversationId is an integer that identifies the current conversation. The value of setAction() is an intent filter identifier for heard messages which is defined in your app manifest, as shown in Define read and reply intent filters.

If your app supports replying to conversations, you also create a PendingIntent for each conversation to notify your app that the user has replied. The following code example shows you how to build this intent for use with a particular conversation: 

Intent msgReplyIntent = new Intent()
    .addFlags(Intent.FLAG_INCLUDE_STOPPED_PACKAGES)
    .setAction(com.myapp.messagingservice.ACTION_MESSAGE_REPLY)
    .putExtra("conversation_id", conversationId);

PendingIntent msgReplyPendingIntent = PendingIntent.getBroadcast(
    getApplicationContext(),
    conversationId,
    msgReplyIntent,
    PendingIntent.FLAG_UPDATE_CURRENT);

Once again, conversationId is an integer that uniquely identifies this conversation. The value of setAction() is an intent filter identifier for replies which is defined in your app manifest, as shown in Define read and reply intent filters.

Sending Messages

When a message arrives for a conversation, you take the following steps to dispatch it as a notification to Auto.

First, add the message to the NotificationCompat.CarExtender.UnreadConversation.Builder for this conversation, and update its timestamp:

unreadConvBuilder.addMessage(messageString)
    .setLatestTimestamp(currentTimestamp);

Then create a NotificationCompat.Builder object that you'll use to build the actual notification. You'll need to use the pending intents you created in the previous step.

NotificationCompat.Builder notificationBuilder =
    new NotificationCompat.Builder(getApplicationContext())
        .setSmallIcon(R.drawable.notification_icon)
        .setLargeIcon(icon_bitmap)
        .setContentText(messageString)
        .setWhen(currentTimestamp)
        .setContentTitle(participant_name)
        .setContentIntent(msgHeardPendingIntent);

You'll also need to extend the NotificationCompat.Builder with the NotificationCompat.CarExtender. This is where you actually create the NotificationCompat.CarExtender.UnreadConversation object using the builder you just created, and attach it to the NotificationCompat.CarExtender:

notificationBuilder.extend(new CarExtender()
    .setUnreadConversation(unreadConvBuilder.build());

Once you've done all this, you use your app's NotificationManagerCompat to send the notification:

NotificationManagerCompat msgNotificationManager =
    NotificationManagerCompat.from(context);
msgNotificationManager.notify(notificationId, notificationBuilder.build());

Handle User Actions

When your create and dispatch a notification for messaging, you specify intents to be triggered when the Auto user hears the message and when the user dictates a reply. Your app indicates to the Android framework that it handles these intends by registering them through it's manifest, as discussed in Define read and reply intent filters.

In addition to registering these intent filters, your app must provide code to handle these actions. Your app can do this by providing a service or BroadcastReceiver objects that handle these intents.

For more information about intents, see Intents and Intent Filters.

Handling a message heard action

When a user listens to a messaging conversation through the Auto user interface, the dashboard device sends a read intent based on how your app defined the messaging notification. Your app catches that intent and invokes the broadcast receiver class associated with it, or the service method set up to handle that action.

The following code example shows how to define a BroadcastReceiver class to handle a received message heard intent: 

public class MessageHeardReceiver extends BroadcastReceiver {

    @Override
    public void onReceive(Context context, Intent intent) {

        // If you set up the intent as described in
        // "Create conversation read and reply intents",
        // you can get the conversation ID by calling:
        int conversationId = intent.getIntExtra("conversation_id", -1);

        // Remove the notification to indicate it has been read
        // and update the list of unread conversations in your app.
    }
}

Once a notification is read, your app can remove it by calling cancel(int) with the notification ID. Within your app, you should mark the messages provided in the notification as read.

Note: An alternative to this implementation is to use a service in a PendingIntent.

Handling a reply action

When a user replies to a messaging conversation through the Auto user interface, the dashboard system sends a reply intent based on how your app defined the messaging notification. Your app catches that intent and invokes the broadcast receiver class associated with it, or the service method set up to handle that action.

The following code example shows how to define a BroadcastReceiver class to handle a received message reply intent: 

  public class MessageReplyReceiver extends BroadcastReceiver {


    @Override
    public void onReceive(Context context, Intent intent) {
        // If you set up the intent as described in
        // "Create conversation read and reply intents",
        // you can get the conversation ID by calling:
        int conversationId = intent.getIntExtra("conversation_id", -1).

    }

    /**
     * Get the message text from the intent.
     * Note that you should call
     * RemoteInput.getResultsFromIntent() to process
     * the RemoteInput.
     */
    private CharSequence getMessageText(Intent intent) {
        Bundle remoteInput =
            RemoteInput.getResultsFromIntent(intent);
        if (remoteInput != null) {
            return remoteInput.getCharSequence("extra_voice_reply");
        }
        return null;
    }

}
Next Get started Next class