[ios] Guard against annotation reuse when there is no identifier

This protects against a crash that would occur when view reuse was
attempted in cases where the map view delegate did not ask for it.
It also fixes a bug where annotation views were attempted when
the map view delegate did not implement the correct delegate method.

It also moves the call to `updateAnnotationViews` back to
`glkView:drawInRect` since doing it in `notifyMapChange`
introduced lag. Additional optimizations may occur in future commits
to make the work required to hide and show views and handle view
reuse less intensive.

In addition, the example MBXAnnotationView is simplified to just
a programatic view with a center panel that can change color. The
color changing center panel is used to indicate if a vie has
gone through the reuse queue.

platform/ios/app/MBXAnnotationView.m

@@ -2,24 +2,20 @@
 
 @interface MBXAnnotationView ()
 
-@property (weak, nonatomic) IBOutlet UIView *centerView;
+@property (nonatomic) UIView *centerView;
 
 @end
 
 @implementation MBXAnnotationView
 
-- (instancetype)initWithCoder:(NSCoder *)coder
-{
-    self = [super initWithCoder:coder];
-    if (self) {
-        self.layer.cornerRadius = CGRectGetWidth(self.bounds) / 2.0;
-    }
-    return self;
-}
-
 - (void)layoutSubviews {
     [super layoutSubviews];
-    self.centerView.layer.cornerRadius = CGRectGetWidth(self.centerView.bounds) / 2.0;
+    if (!self.centerView) {
+        self.backgroundColor = [UIColor blueColor];
+        self.centerView = [[UIView alloc] initWithFrame:CGRectMake(5,5, CGRectGetWidth(self.bounds) - 10, CGRectGetWidth(self.bounds) - 10)];
+        self.centerView.backgroundColor = self.centerColor;
+        [self addSubview:self.centerView];
+    }
 }
 
 - (void)setCenterColor:(UIColor *)centerColor {

platform/ios/app/MBXViewController.m

@@ -612,10 +612,13 @@ - (void)dealloc
 - (MGLAnnotationView *)mapView:(MGLMapView *)mapView viewForAnnotation:(id<MGLAnnotation>)annotation
 {
     MBXAnnotationView *annotationView = (MBXAnnotationView *)[mapView dequeueReusableAnnotationViewWithIdentifier:@"MBXAnnotationView"];
-    annotationView.centerColor = [UIColor redColor];
     if (!annotationView)
     {
-        annotationView = [[[NSBundle mainBundle] loadNibNamed:@"MBXAnnotationView" owner:self options:nil] objectAtIndex:0];
+        annotationView = [[MBXAnnotationView alloc] initWithFrame:CGRectMake(0, 0, 40, 40)];
+        annotationView.centerColor = [UIColor whiteColor];
+    } else {
+        // orange indicates that the annotation view was reused
+        annotationView.centerColor = [UIColor orangeColor];
     }
     return annotationView;
 }

platform/ios/ios.xcodeproj/project.pbxproj

@@ -7,7 +7,6 @@
 	objects = {
 
 /* Begin PBXBuildFile section */
-		400165041CCFC618005583CC /* MBXAnnotationView.xib in Resources */ = {isa = PBXBuildFile; fileRef = 400165031CCFC618005583CC /* MBXAnnotationView.xib */; };
 		40FC668F1CCE8D6000AFCF7D /* MGLAnnotationView_Private.h in Headers */ = {isa = PBXBuildFile; fileRef = 40FC668B1CCE8CFC00AFCF7D /* MGLAnnotationView_Private.h */; };
 		40FC66901CCE8D6A00AFCF7D /* MGLAnnotationView.h in Headers */ = {isa = PBXBuildFile; fileRef = 40FC668C1CCE8D4F00AFCF7D /* MGLAnnotationView.h */; settings = {ATTRIBUTES = (Public, ); }; };
 		40FC66911CCE8D6A00AFCF7D /* MGLAnnotationView.m in Sources */ = {isa = PBXBuildFile; fileRef = 40FC668D1CCE8D4F00AFCF7D /* MGLAnnotationView.m */; };
@@ -311,7 +310,6 @@
 /* End PBXCopyFilesBuildPhase section */
 
 /* Begin PBXFileReference section */
-		400165031CCFC618005583CC /* MBXAnnotationView.xib */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = file.xib; path = MBXAnnotationView.xib; sourceTree = "<group>"; };
 		40FC668B1CCE8CFC00AFCF7D /* MGLAnnotationView_Private.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; name = MGLAnnotationView_Private.h; path = src/MGLAnnotationView_Private.h; sourceTree = "<group>"; };
 		40FC668C1CCE8D4F00AFCF7D /* MGLAnnotationView.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; name = MGLAnnotationView.h; path = src/MGLAnnotationView.h; sourceTree = "<group>"; };
 		40FC668D1CCE8D4F00AFCF7D /* MGLAnnotationView.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; name = MGLAnnotationView.m; path = src/MGLAnnotationView.m; sourceTree = "<group>"; };
@@ -558,7 +556,6 @@
 				DA1DC9981CB6E054006E619F /* MBXAppDelegate.m */,
 				40FDA7691CCAAA6800442548 /* MBXAnnotationView.h */,
 				40FDA76A1CCAAA6800442548 /* MBXAnnotationView.m */,
-				400165031CCFC618005583CC /* MBXAnnotationView.xib */,
 				DA1DC9661CB6C6B7006E619F /* MBXCustomCalloutView.h */,
 				DA1DC9671CB6C6B7006E619F /* MBXCustomCalloutView.m */,
 				DA1DC9681CB6C6B7006E619F /* MBXOfflinePacksTableViewController.h */,

platform/ios/src/MGLMapView.mm

@@ -861,6 +861,7 @@ - (void)glkView:(__unused GLKView *)view drawInRect:(__unused CGRect)rect
     {
         _mbglMap->render();
 
+        [self updateAnnotationViews];
         [self updateUserLocationAnnotationView];
     }
 }
@@ -2792,8 +2793,9 @@ - (void)addAnnotations:(NS_ARRAY_OF(id <MGLAnnotation>) *)annotations
 
             if (delegateImplementsViewForAnnotation)
             {
-                annotationView = [self addAnnotationViewWithAnnotation:annotation];
-                if (annotationView) {
+                annotationView = [self annotationViewForAnnotation:annotation];
+                if (annotationView)
+                {
                     annotationViewsForAnnotation[annotationValue] = annotationView;
                     annotationView.center = [self convertCoordinate:annotation.coordinate toPointToView:self];
                     [self.glView addSubview:annotationView];
@@ -2901,7 +2903,7 @@ - (MGLAnnotationImage *)defaultAnnotationImage
     return annotationImage;
 }
 
-- (MGLAnnotationView *)addAnnotationViewWithAnnotation:(id<MGLAnnotation>)annotation
+- (MGLAnnotationView *)annotationViewForAnnotation:(id<MGLAnnotation>)annotation
 {
     MGLAnnotationView *annotationView = (MGLAnnotationView *)[self.delegate mapView:self viewForAnnotation:annotation];
 
@@ -4236,9 +4238,6 @@ - (void)notifyMapChange:(mbgl::MapChange)change
             {
                 [self.delegate mapViewRegionIsChanging:self];
             }
-
-            [self updateAnnotationViews];
-
             break;
         }
         case mbgl::MapChangeRegionDidChange:
@@ -4326,21 +4325,29 @@ - (void)updateUserLocationAnnotationView
 
 - (void)updateAnnotationViews
 {
+    BOOL delegateImplementsViewForAnnotation = [self.delegate respondsToSelector:@selector(mapView:viewForAnnotation:)];
+
+    if (!delegateImplementsViewForAnnotation)
+    {
+        return;
+    }
+
     // Update all visible annotation views
     std::set<MGLAnnotationTag> visibleTags;
-    std::vector<MGLAnnotationTag> annotationTags = [self annotationTagsInRect:CGRectInset(self.bounds, -50, -50)];
+    std::vector<MGLAnnotationTag> annotationTags = [self annotationTagsInRect:self.bounds];
+
     for(auto const& annotationTag: annotationTags)
     {
         auto &annotationContext = _annotationContextsByAnnotationTag[annotationTag];
         id<MGLAnnotation> annotation = annotationContext.annotation;
+
         CGPoint annotationPoint = [self convertCoordinate:annotation.coordinate toPointToView:self];
 
         // If there is no annotation view at this point, it means the context's view was reused by some
-        // other context so we need to reuse or make a new view. If we do get here, it does mean
-        // that th delegate supports annotation views so it is safe to ask it for another one
+        // other context so we need to reuse or make a new view.
         if (!annotationContext.annotationView)
         {
-            MGLAnnotationView *annotationView = [self addAnnotationViewWithAnnotation:annotation];
+            MGLAnnotationView *annotationView = [self annotationViewForAnnotation:annotation];
 
             if (annotationView)
             {
@@ -4353,27 +4360,34 @@ - (void)updateAnnotationViews
                 annotationContext.annotationView = annotationView;
             }
         }
-        
+
         annotationContext.annotationView.center = annotationPoint;
         annotationContext.annotationView.hidden = NO;
+
         visibleTags.insert(annotationTag);
     }
 
-    // Add offscreen annotation views to reuse queue
+    // Hide and add offscreen annotation views to reuse queue
     for (auto &pair : _annotationContextsByAnnotationTag)
     {
         MGLAnnotationTag annotationTag = pair.first;
         MGLAnnotationContext &annotationContext = pair.second;
         MGLAnnotationView *annotationView = annotationContext.annotationView;
-        NSMutableArray *annotationViewReuseQueue = [self annotationViewReuseQueueForIdentifier:annotationContext.viewReuseIdentifier];
-
         const bool tagIsNotVisible = visibleTags.find(annotationTag) == visibleTags.end();
-
-        if (tagIsNotVisible && annotationView && ![annotationViewReuseQueue containsObject:annotationView])
+        
+        if (annotationView && tagIsNotVisible)
         {
-            [annotationViewReuseQueue addObject:annotationView];
             annotationView.hidden = YES;
-            annotationContext.annotationView = NULL;
+
+            if (annotationContext.viewReuseIdentifier)
+            {
+                NSMutableArray *annotationViewReuseQueue = [self annotationViewReuseQueueForIdentifier:annotationContext.viewReuseIdentifier];
+                if (![annotationViewReuseQueue containsObject:annotationView])
+                {
+                    [annotationViewReuseQueue addObject:annotationView];
+                    annotationContext.annotationView = nil;
+                }
+            }
         }
     }
 }