Sync sample prebuilts for lmp-mr1-ub-docs

Synced to //developers/samples/android commit
7e6f96a4bd8d07daf2f9e464dad32e7daa62999b

Change-Id: I3c44d32aca1a5513f52e71f28d1848a055d03aab

2 files changed, 13 insertions, 2 deletions

diff --git a/samples/browseable/AlwaysOn/AndroidManifest.xml b/samples/browseable/AlwaysOn/AndroidManifest.xml
index c0fce9f27..12c4b03a5 100644
--- a/samples/browseable/AlwaysOn/AndroidManifest.xml
+++ b/samples/browseable/AlwaysOn/AndroidManifest.xml
@@ -30,6 +30,12 @@
         <!--If you want your app to run on pre-22, then set required to false -->
         <uses-library android:name="com.google.android.wearable" android:required="false" />
 
+        <!--
+            To update the screen more than once per minute in ambient mode, developers should set
+            the launch mode for the activity to single instance. Otherwise, the AlarmManager launch
+            intent will open a new activity every time the Alarm is triggered rather than reusing
+            the same (already active) Activity.
+        -->
         <activity android:name="com.example.android.wearable.wear.alwayson.MainActivity"
             android:label="@string/app_name"
             android:launchMode="singleInstance"
diff --git a/samples/browseable/AlwaysOn/src/com.example.android.wearable.wear.alwayson/MainActivity.java b/samples/browseable/AlwaysOn/src/com.example.android.wearable.wear.alwayson/MainActivity.java
index 51f287d81..0eb7f470d 100644
--- a/samples/browseable/AlwaysOn/src/com.example.android.wearable.wear.alwayson/MainActivity.java
+++ b/samples/browseable/AlwaysOn/src/com.example.android.wearable.wear.alwayson/MainActivity.java
@@ -255,10 +255,15 @@ public class MainActivity extends WearableActivity {
         long timeMs = System.currentTimeMillis();
 
         if (isAmbient()) {
-            /** Prevents time drift while calculating trigger time (based on state). */
+            /** Calculate next trigger time (based on state). */
             long delayMs = AMBIENT_INTERVAL_MS - (timeMs % AMBIENT_INTERVAL_MS);
             long triggerTimeMs = timeMs + delayMs;
 
+            /**
+             * Note: Make sure you have set activity launchMode to singleInstance in the manifest.
+             * Otherwise, it is easy for the AlarmManager launch intent to open a new activity
+             * every time the Alarm is triggered rather than reusing this Activity.
+             */
             mAmbientStateAlarmManager.cancel(mAmbientStatePendingIntent);
             mAmbientStateAlarmManager.setExact(
                     AlarmManager.RTC_WAKEUP,
@@ -266,7 +271,7 @@ public class MainActivity extends WearableActivity {
                     mAmbientStatePendingIntent);
 
         } else {
-            /** Prevents time drift. */
+            /** Calculate next trigger time (based on state). */
             long delayMs = ACTIVE_INTERVAL_MS - (timeMs % ACTIVE_INTERVAL_MS);
 
             mActiveModeUpdateHandler.removeMessages(MSG_UPDATE_SCREEN);