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. +
+ + ++ 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:
+ ++ 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. +
+ + ++ 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 {@code + res/xml/} your app's development project directory as {@code 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. +
+ + ++ Auto devices use {@link android.content.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 {@code + android.content.BroadcastReceiver} classes that handle them in the manifest. The following code + example demonstrates how to declare these intents and thier 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 {@code android.content.BroadcastReceiver} classes shown in this example + is discussed in Handle User Actions. +
+ + ++ 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 21.1.0 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-v4:21.1.+'
+}
+
+
++ For information about importing the support library into development projects for other + development environments, see Support + Library Setup. +
+ + + ++ 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. +
+ + ++ Messaging notifications for Auto organize messages into conversations using the {@code + 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 {@code 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 {@link android.app.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 {@code setReplyAction()} + method and provide a pending intent to pass that user action back to your app. The {@code + UnreadConversation} object you create must also include a {@link + android.support.v4.app.RemoteInput} object. This object is required because the Auto user + receiving this conversation speaks a reply, a the remote input objects lets your app get a text + version of the voice reply. +
+ + ++ Messages provided for Auto must be associated with a conversation using the {@code + 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. +
+ + ++ Unread conversation objects contain intents for reading and replying to a conversation. You + create a {@link android.app.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 {@link android.app.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, {@code conversationId} is an integer that identifies the current conversation. + The value of {@code 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 {@link + android.app.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, {@code conversationId} is an integer that uniquely identifies this conversation. The + value of {@code setAction()} is an intent filter identifier for replies which is defined in your + app manifest, as shown in Define read and reply intent filters. +
+ + ++ 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 UnreadConversation.Builder for
+this conversation, and update its timestamp:
+unreadConvBuilder.addMessage(messageString) + .setLatestTimestamp(currentTimestamp); ++ +
Then create a {@link android.support.v4.app.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 {@link
+android.support.v4.app.NotificationCompat.Builder} with the
+CarExtender. This is where you actually create the
+UnreadConversation object using the builder you just
+created, and attach it to the CarExtender:
+notificationBuilder.extend(new CarExtender() + .setUnreadConversation(unreadConvBuilder.build()); ++ +
Once you've done all this, you use your app's {@link +android.support.v4.app.NotificationManagerCompat} to send the notification:
+ ++mNotificationManager = NotificationManagerCompat.from(context); +mNotificationManager.notify(notificationId, notificationBuilder.build()); ++ +
In this example, msgNotificationManager is a +{@link android.support.v4.app.NotificationManagerCompat} you created for your app.
+ + ++ 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 {@link android.content.BroadcastReceiver} + objects that handle these intents.
+ ++ For more information about intents, see Intents and Intent Filters. +
+ + ++ 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 {@link android.content.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 + {@link android.support.v4.app.NotificationManagerCompat#cancel} 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 + {@link android.app.PendingIntent}. +
+ + ++ 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 {@link android.content.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;
+ }
+
+}
diff --git a/docs/html/training/training_toc.cs b/docs/html/training/training_toc.cs
index 791aef6ef9731..61a5e3c4dd355 100644
--- a/docs/html/training/training_toc.cs
+++ b/docs/html/training/training_toc.cs
@@ -959,6 +959,11 @@ include the action bar on devices running Android 2.1 or higher."
description="How to extend audio apps to play content on Auto devices.">
Playing Audio for Auto
+