Implementing Android Player
This section describes configuring Android player. It provides information of the configuration file and the options available and recommendations as to which settings to use for development and testing.
Additionally, Watchdog is a solution to recover the player from crashes. An application needs to register itself with the watchdog service and then periodically send messages to the service that it is alive. In case the watchdog service does not receive a keep-alive message within a stipulated time, the service attempts to reboot the device for a clean recovery (if it has the sufficient privileges) or restart the application.
Installing Android Player
To implement Android Player for AEM Screens, please install Android Player for AEM Screens.
Visit the AEM 6.4 Player Downloads page.
The Ad-Hoc method allows you to install the latest Android Player ( .exe ). Visit AEM 6.4 Player Downloads page.
Once you download the application, follow the steps on the player to complete the ad-hoc installation:
- Long-press on the top left corner to open the admin panel.
- Navigate to Configuration from the left action menu and enter the location (address) of the AEM instance you wish to connect to and click Save .
- Navigate to the Device Registration link from the left action menu to check the status ofthedevice registration process.
If the State is REGISTERED , you will notice the Device id field will be populated.
If the State is UNREGISTERED , you can use the Token to register the device.
Implementing Android Watchdog
Due to Android's architecture, rebooting the device requires that the application has system privileges. To do this, you need to sign the apk using the manufacturer's signing keys, otherwise watchdog will restart the player application and not reboot the device.
Signage of Android apks using Manufacturer Keys
To access some of the privileged APIs of Android such as PowerManager or HDMIControlServices , you need to signtheandroid apk using the manufacturer's keys.
You should have the android SDK installed, before you perform the following steps.
Follow the steps below to sign the android apk using the manufacturer's keys:
- Download the apk from Google Play or from AEM Screens Player Downloads page
- Obtain the platform keys from the manufacturer to get a pk8 and a pem file
- Locate the apksigner tool in android sdk using find ~/Library/Android/sdk/build-tools -name "apksigner"
- <pathto> /apksigner sign --key platform.pk8 --cert platform.x509.pem aemscreensplayer.apk
- Find the path to the zip align tool in android sdk
- <pathto> /zipalign -fv 4 aemscreensplayer.apk aemscreensaligned.apk
- Install aemscreensaligned.apk using adb install to the device
Android Watchdog Implementation
The cross-Android watchdog service is implemented as a cordova plugin using AlarmManager .
The following diagram shows the implementation of watchdog service:
1. Initialization At the time of initialization of the cordova plugin, permissions are checked to see if we have system privileges and thus the Reboot permission. If these two criteria are met, a pending Intent for Reboot is created, otherwise a pending Intent to restart the application (based on its Launch Activity) is created.
2. Keep Alive Timer A keep alive timer is used to trigger an event every 15 seconds. In that event, you need to cancel the existing pending intent (to reboot or restart the app) and register a new pending intent for the same 60 seconds in the future (essentially postponing reboot).
In Android, the AlarmManager is used to register the pendingIntents that can execute even if the app has crashed and its alarm delivery is inexact from API 19 (Kitkat). Keep some spacing between the timer's interval and the AlarmManager's pendingIntent's alarm.
3. Application Crash In case of a crash, the pendingIntent for Reboot registered with AlarmManager is no longer reset and thus it executes a reboot or restart of app (depending on permissions available at the time of initialization of the cordova plugin).