explicitly release androids mediaplayer when component is unmounted (#319)

android/src/main/java/com/brentvatne/react/ReactVideoView.java

@@ -148,6 +148,17 @@ public class ReactVideoView extends ScalableVideoView implements MediaPlayer.OnP
         }
     }
 
+    public void cleanupMediaPlayerResources() {
+        if ( mediaController != null ) {
+            mediaController.hide();
+        }
+        if ( mMediaPlayer != null ) {
+            mMediaPlayerValid = false;
+            mMediaPlayer.stop();
+            mMediaPlayer.release();
+        }
+    }
+
     public void setSrc(final String uriString, final String type, final boolean isNetwork, final boolean isAsset) {
 
         mSrcUriString = uriString;

android/src/main/java/com/brentvatne/react/ReactVideoViewManager.java

@@ -43,6 +43,12 @@ public class ReactVideoViewManager extends SimpleViewManager<ReactVideoView> {
         return new ReactVideoView(themedReactContext);
     }
 
+    @Override
+    public void onDropViewInstance(ReactVideoView view) {
+        super.onDropViewInstance(view);
+        view.cleanupMediaPlayerResources();
+    }
+
     @Override
     @Nullable
     public Map getExportedCustomDirectEventTypeConstants() {