Added calls for setting the away presence

app/src/main/java/chat/rocket/android/activity/MainActivity.java

@@ -7,9 +7,11 @@ import android.support.v7.widget.Toolbar;
 import android.view.View;
 import chat.rocket.android.LaunchUtil;
 import chat.rocket.android.R;
+import chat.rocket.android.api.MethodCallHelper;
 import chat.rocket.android.fragment.chatroom.HomeFragment;
 import chat.rocket.android.fragment.chatroom.RoomFragment;
 import chat.rocket.android.fragment.sidebar.SidebarMainFragment;
+import chat.rocket.android.helper.LogcatIfError;
 import chat.rocket.android.model.internal.Session;
 import chat.rocket.android.realm_helper.RealmHelper;
 import chat.rocket.android.realm_helper.RealmObjectObserver;
@@ -37,6 +39,34 @@ public class MainActivity extends AbstractAuthedActivity {
     }
   }
 
+  @Override
+  protected void onStart() {
+    super.onStart();
+
+    setUserOnlineIfServerAvailable();
+  }
+
+  @Override
+  protected void onStop() {
+    setUserAwayIfServerAvailable();
+
+    super.onStop();
+  }
+
+  private void setUserOnlineIfServerAvailable() {
+    if (serverConfigId != null) {
+      new MethodCallHelper(this, serverConfigId).setUserOnline()
+          .continueWith(new LogcatIfError());
+    }
+  }
+
+  private void setUserAwayIfServerAvailable() {
+    if (serverConfigId != null) {
+      new MethodCallHelper(this, serverConfigId).setUserAway()
+          .continueWith(new LogcatIfError());
+    }
+  }
+
   private void setupSidebar() {
     SlidingPaneLayout pane = (SlidingPaneLayout) findViewById(R.id.sliding_pane);
     if (pane != null) {

app/src/main/java/chat/rocket/android/api/MethodCallHelper.java

@@ -278,6 +278,15 @@ public class MethodCallHelper {
         .onSuccessTask(task -> Task.forResult(null));
   }
 
+  public Task<Void> setUserAway() {
+    return call("UserPresence:away", TIMEOUT_MS, JSONArray::new)
+        .onSuccessTask(task -> Task.forResult(null));
+  }
+
+  public Task<Void> setUserOnline() {
+    return call("UserPresence:online", TIMEOUT_MS, JSONArray::new)
+        .onSuccessTask(task -> Task.forResult(null));
+  }
 
   public Task<JSONObject> getUsersOfRoom(final String roomId, final boolean showAll) {
     return call("getUsersOfRoom", TIMEOUT_MS, () -> new JSONArray().put(roomId).put(showAll))