Add setInitialRoute on FlutterViewController (#3754)

shell/platform/darwin/ios/framework/Headers/FlutterViewController.h

@@ -20,6 +20,14 @@ FLUTTER_EXPORT
                          bundle:(NSBundle*)nibBundleOrNil NS_DESIGNATED_INITIALIZER;
 
 - (void)handleStatusBarTouches:(UIEvent*)event;
+
+/**
+ Sets the first route that the Flutter app shows. The default is "/".
+
+ - Parameter route: The name of the first route to show.
+ */
+- (void)setInitialRoute:(NSString*)route;
+
 @end
 
 #endif  // FLUTTER_FLUTTERVIEWCONTROLLER_H_

shell/platform/darwin/ios/framework/Source/FlutterViewController.mm

@@ -72,6 +72,7 @@ class PlatformMessageResponseDarwin : public blink::PlatformMessageResponse {
   fml::scoped_nsprotocol<FlutterBasicMessageChannel*> _lifecycleChannel;
   fml::scoped_nsprotocol<FlutterBasicMessageChannel*> _systemChannel;
   BOOL _initialized;
+  BOOL _connected;
 }
 
 + (void)initialize {
@@ -164,7 +165,6 @@ class PlatformMessageResponseDarwin : public blink::PlatformMessageResponse {
 
   [self setupNotificationCenterObservers];
 
-  [self connectToEngineAndLoad];
 }
 
 - (void)setupNotificationCenterObservers {
@@ -225,6 +225,11 @@ class PlatformMessageResponseDarwin : public blink::PlatformMessageResponse {
                object:nil];
 }
 
+
+- (void)setInitialRoute:(NSString*)route {
+  [_navigationChannel.get() invokeMethod:@"setInitialRoute"
+                               arguments:route];
+}
 #pragma mark - Initializing the engine
 
 - (void)alertView:(UIAlertView*)alertView clickedButtonAtIndex:(NSInteger)buttonIndex {
@@ -232,6 +237,10 @@ class PlatformMessageResponseDarwin : public blink::PlatformMessageResponse {
 }
 
 - (void)connectToEngineAndLoad {
+  if (_connected)
+    return;
+  _connected = YES;
+
   TRACE_EVENT0("flutter", "connectToEngineAndLoad");
 
   // We ask the VM to check what it supports.
@@ -264,6 +273,11 @@ class PlatformMessageResponseDarwin : public blink::PlatformMessageResponse {
   [view release];
 }
 
+- (void)viewWillAppear:(BOOL)animated {
+  [self connectToEngineAndLoad];
+  [super viewWillAppear:animated];
+}
+
 #pragma mark - Application lifecycle notifications
 
 - (void)applicationBecameActive:(NSNotification*)notification {