add function to change subtitles style

library/src/main/java/com/google/android/exoplayer2/ui/SimpleExoPlayerView.java

@@ -39,6 +39,7 @@ import com.google.android.exoplayer2.Timeline;
 import com.google.android.exoplayer2.metadata.Metadata;
 import com.google.android.exoplayer2.metadata.id3.ApicFrame;
 import com.google.android.exoplayer2.source.TrackGroupArray;
+import com.google.android.exoplayer2.text.CaptionStyleCompat;
 import com.google.android.exoplayer2.text.Cue;
 import com.google.android.exoplayer2.text.TextRenderer;
 import com.google.android.exoplayer2.trackselection.TrackSelection;
@@ -478,6 +479,12 @@ public final class SimpleExoPlayerView extends FrameLayout {
     return useController ? controller.dispatchKeyEvent(event) : super.dispatchKeyEvent(event);
   }
 
+  public void setSubtitleStyle(CaptionStyleCompat style) {
+
+    if (subtitleView != null)
+      subtitleView.setStyle(style);
+  }
+
   private void maybeShowController(boolean isForced) {
     if (!useController || player == null) {
       return;