Prepare Dark Theme

Observe user interface theme change.

https://github.com/vector-im/riot-meta/issues/22

Riot/ViewController/RoomParticipantsViewController.m

@@ -59,6 +59,9 @@
     NSLayoutConstraint *addParticipantButtonImageViewBottomConstraint;
     
     UIAlertController *currentAlert;
+    
+    // Observe kRiotDesignValuesDidChangeThemeNotification to handle user interface theme change.
+    id kRiotDesignValuesDidChangeThemeNotificationObserver;
 }
 
 @end
@@ -86,7 +89,6 @@
     [super finalizeInit];
     
     // Setup `MXKViewControllerHandling` properties
-    self.defaultBarTintColor = kRiotNavBarTintColor;
     self.enableBarTintColorStatusChange = NO;
     self.rageShakeManager = [RageShakeManager sharedManager];
 }
@@ -145,6 +147,19 @@
     
     // Add room creation button programmatically
     [self addAddParticipantButton];
+    
+    // Observe user interface theme change.
+    kRiotDesignValuesDidChangeThemeNotificationObserver = [[NSNotificationCenter defaultCenter] addObserverForName:kRiotDesignValuesDidChangeThemeNotification object:nil queue:[NSOperationQueue mainQueue] usingBlock:^(NSNotification *notif) {
+        
+        [self userInterfaceThemeDidChange];
+        
+    }];
+    [self userInterfaceThemeDidChange];
+}
+
+- (void)userInterfaceThemeDidChange
+{
+    self.defaultBarTintColor = kRiotSecondaryBgColor;
 }
 
 // This method is called when the viewcontroller is added or removed from a container view controller.
@@ -157,6 +172,12 @@
 
 - (void)destroy
 {
+    if (kRiotDesignValuesDidChangeThemeNotificationObserver)
+    {
+        [[NSNotificationCenter defaultCenter] removeObserver:kRiotDesignValuesDidChangeThemeNotificationObserver];
+        kRiotDesignValuesDidChangeThemeNotificationObserver = nil;
+    }
+    
     if (leaveRoomNotificationObserver)
     {
         [[NSNotificationCenter defaultCenter] removeObserver:leaveRoomNotificationObserver];