Added onTimedMetadata callback for iOS player and Exoplayer (#487)

* added listener for timedMetadata event.

* added callback in RCTVideo for the timed metadata

* exposing onTimedMetadata to JS

* added forgotten method declaration

* returning array of string values

* added metadata type to the array

* added onMetadata method

* overridden onMetadata method on exoplayer2

* added format of return value from onMetadata

* added function reference in README file

ios/RCTVideo.h

@@ -16,6 +16,7 @@
 @property (nonatomic, copy) RCTBubblingEventBlock onVideoProgress;
 @property (nonatomic, copy) RCTBubblingEventBlock onVideoSeek;
 @property (nonatomic, copy) RCTBubblingEventBlock onVideoEnd;
+@property (nonatomic, copy) RCTBubblingEventBlock onTimedMetadata;
 @property (nonatomic, copy) RCTBubblingEventBlock onVideoFullscreenPlayerWillPresent;
 @property (nonatomic, copy) RCTBubblingEventBlock onVideoFullscreenPlayerDidPresent;
 @property (nonatomic, copy) RCTBubblingEventBlock onVideoFullscreenPlayerWillDismiss;

ios/RCTVideo.m

@@ -9,6 +9,7 @@ static NSString *const playbackLikelyToKeepUpKeyPath = @"playbackLikelyToKeepUp"
 static NSString *const playbackBufferEmptyKeyPath = @"playbackBufferEmpty";
 static NSString *const readyForDisplayKeyPath = @"readyForDisplay";
 static NSString *const playbackRate = @"rate";
+static NSString *const timedMetadata = @"timedMetadata";
 
 @implementation RCTVideo
 {
@@ -226,6 +227,7 @@ static NSString *const playbackRate = @"rate";
   [_playerItem addObserver:self forKeyPath:statusKeyPath options:0 context:nil];
   [_playerItem addObserver:self forKeyPath:playbackBufferEmptyKeyPath options:0 context:nil];
   [_playerItem addObserver:self forKeyPath:playbackLikelyToKeepUpKeyPath options:0 context:nil];
+  [_playerItem addObserver:self forKeyPath:timedMetadata options:NSKeyValueObservingOptionNew context:nil];
   _playerItemObserversSet = YES;
 }
 
@@ -238,6 +240,7 @@ static NSString *const playbackRate = @"rate";
     [_playerItem removeObserver:self forKeyPath:statusKeyPath];
     [_playerItem removeObserver:self forKeyPath:playbackBufferEmptyKeyPath];
     [_playerItem removeObserver:self forKeyPath:playbackLikelyToKeepUpKeyPath];
+    [_playerItem removeObserver:self forKeyPath:timedMetadata];
     _playerItemObserversSet = NO;
   }
 }
@@ -318,6 +321,34 @@ static NSString *const playbackRate = @"rate";
 {
    if (object == _playerItem) {
 
+    // When timeMetadata is read the event onTimedMetadata is triggered
+    if ([keyPath isEqualToString: timedMetadata])
+    {
+
+        
+        NSArray<AVMetadataItem *> *items = [change objectForKey:@"new"];
+        if (items && ![items isEqual:[NSNull null]] && items.count > 0) {
+            
+            NSMutableArray *array = [NSMutableArray new];
+            for (AVMetadataItem *item in items) {
+                
+                NSString *value = item.value;
+                NSString *identifier = item.identifier;
+                
+                if (![value isEqual: [NSNull null]]) {
+                    NSDictionary *dictionary = [[NSDictionary alloc] initWithObjects:@[value, identifier] forKeys:@[@"value", @"identifier"]];
+                    
+                    [array addObject:dictionary];
+                }
+            }
+            
+            self.onTimedMetadata(@{
+                                   @"target": self.reactTag,
+                                   @"metadata": array
+                                   });
+        }
+    }
+
     if ([keyPath isEqualToString:statusKeyPath]) {
       // Handle player item status change.
       if (_playerItem.status == AVPlayerItemStatusReadyToPlay) {

ios/RCTVideoManager.m

@@ -41,6 +41,7 @@ RCT_EXPORT_VIEW_PROPERTY(onVideoError, RCTBubblingEventBlock);
 RCT_EXPORT_VIEW_PROPERTY(onVideoProgress, RCTBubblingEventBlock);
 RCT_EXPORT_VIEW_PROPERTY(onVideoSeek, RCTBubblingEventBlock);
 RCT_EXPORT_VIEW_PROPERTY(onVideoEnd, RCTBubblingEventBlock);
+RCT_EXPORT_VIEW_PROPERTY(onTimedMetadata, RCTBubblingEventBlock);
 RCT_EXPORT_VIEW_PROPERTY(onVideoFullscreenPlayerWillPresent, RCTBubblingEventBlock);
 RCT_EXPORT_VIEW_PROPERTY(onVideoFullscreenPlayerDidPresent, RCTBubblingEventBlock);
 RCT_EXPORT_VIEW_PROPERTY(onVideoFullscreenPlayerWillDismiss, RCTBubblingEventBlock);