[ios] Fixes an issue that caused a timer run in a background thread.

Author: fabian-guerra

Examples/ObjectiveC/AnimatedLineExample.m

@@ -59,10 +59,13 @@ - (void)animatePolyline {
     self.currentIndex = 1;
 
     // Start a timer that will simulate adding points to our polyline. This could also represent coordinates being added to our polyline from another source, such as a CLLocationManagerDelegate.
-    self.timer = [NSTimer scheduledTimerWithTimeInterval:0.05 target:self selector:@selector(tick:) userInfo:nil repeats:YES];
+    self.timer = [NSTimer timerWithTimeInterval:0.05 target:self selector:@selector(tick:) userInfo:nil repeats:YES];
+    [[NSRunLoop mainRunLoop] addTimer:self.timer forMode:NSRunLoopCommonModes];
 }
 
 - (void)tick:(NSTimer*)timer {
+    NSAssert([[NSThread currentThread] isMainThread], @"%s must be accessed on the main thread, not %@", __PRETTY_FUNCTION__, [NSThread currentThread]);
+    
     if (self.currentIndex > self.locations.count) {
         [self.timer invalidate];
         return;