Update iOS part of flutter_view to use the new platform message channel (#8762)

* Update iOS part of flutter_view to use the new platform message channel

* remove newline

* comments

examples/flutter_view/ios/Podfile.lock

-PODFILE CHECKSUM: 665d7a704fb3ad8037fd80d414eb5db11ba3fc93
+PODFILE CHECKSUM: 638dc8f58cade4b6f922e82e3c1008f507581efd
 
 COCOAPODS: 1.2.0

examples/flutter_view/ios/Pods/Manifest.lock

-PODFILE CHECKSUM: 665d7a704fb3ad8037fd80d414eb5db11ba3fc93
+PODFILE CHECKSUM: 638dc8f58cade4b6f922e82e3c1008f507581efd
 
 COCOAPODS: 1.2.0

examples/flutter_view/ios/Runner/MainViewController.h

@@ -13,7 +13,6 @@
 
 @protocol NativeViewControllerDelegate;
 
-@interface MainViewController : UIViewController <FlutterMessageListener,
-                                                  NativeViewControllerDelegate>
+@interface MainViewController : UIViewController <NativeViewControllerDelegate>
 @end
 

examples/flutter_view/ios/Runner/MainViewController.m

@@ -10,11 +10,13 @@
 
 @interface MainViewController ()
 
-@property (strong, nonatomic) NativeViewController* nativeViewController;
-@property (strong, nonatomic) FlutterViewController* flutterViewController;
+@property (nonatomic) NativeViewController* nativeViewController;
+@property (nonatomic) FlutterViewController* flutterViewController;
+@property (nonatomic) FlutterMessageChannel* messageChannel;
 @end
 
 static NSString* const emptyString = @"";
+static NSString* const ping = @"ping";
 static NSString* const channel = @"increment";
 
 @implementation MainViewController
@@ -23,11 +25,6 @@ static NSString* const channel = @"increment";
   return channel;
 }
 
-- (NSString*)didReceiveString:(NSString*)message {
-  [self.nativeViewController didReceiveIncrement];
-  return emptyString;
-}
-
 - (void)prepareForSegue:(UIStoryboardSegue*)segue sender:(id)sender {
 
   if ([segue.identifier isEqualToString: @"NativeViewControllerSegue"]) {
@@ -36,13 +33,22 @@ static NSString* const channel = @"increment";
   }
 
   if ([segue.identifier isEqualToString:@"FlutterViewControllerSegue"]) {
-     self.flutterViewController = segue.destinationViewController;
-    [self.flutterViewController addMessageListener:self];
+    self.flutterViewController = segue.destinationViewController;
+
+    self.messageChannel = [FlutterMessageChannel messageChannelNamed:channel
+                                                     binaryMessenger:self.flutterViewController
+                                                               codec:[FlutterStringCodec sharedInstance]];
+
+    MainViewController*  __weak weakSelf = self;
+    [self.messageChannel setMessageHandler:^(id message, FlutterReplyHandler replyHandler) {
+      [weakSelf.nativeViewController didReceiveIncrement];
+      replyHandler(emptyString);
+    }];
   }
 }
 
 - (void)didTapIncrementButton {
-  [self.flutterViewController sendString:emptyString withMessageName:self.messageName];
+  [self.messageChannel sendMessage:ping replyHandler:nil];
 }
 
 @end