Allow multiple listeners on TimeBar

Issue: #3406

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=174214296

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

@@ -40,6 +40,7 @@ import com.google.android.exoplayer2.util.Assertions;
 import com.google.android.exoplayer2.util.Util;
 import java.util.Formatter;
 import java.util.Locale;
+import java.util.concurrent.CopyOnWriteArraySet;
 
 /**
  * A time bar that shows a current position, buffered position, duration and ad markers.
@@ -198,8 +199,8 @@ public class DefaultTimeBar extends View implements TimeBar {
   private final StringBuilder formatBuilder;
   private final Formatter formatter;
   private final Runnable stopScrubbingRunnable;
+  private final CopyOnWriteArraySet<OnScrubListener> listeners;
 
-  private OnScrubListener listener;
   private int keyCountIncrement;
   private long keyTimeIncrement;
   private int lastCoarseScrubXPosition;
@@ -231,6 +232,7 @@ public class DefaultTimeBar extends View implements TimeBar {
     playedAdMarkerPaint = new Paint();
     scrubberPaint = new Paint();
     scrubberPaint.setAntiAlias(true);
+    listeners = new CopyOnWriteArraySet<>();
 
     // Calculate the dimensions and paints for drawn elements.
     Resources res = context.getResources();
@@ -325,8 +327,13 @@ public class DefaultTimeBar extends View implements TimeBar {
   }
 
   @Override
-  public void setListener(OnScrubListener listener) {
-    this.listener = listener;
+  public void addListener(OnScrubListener listener) {
+    listeners.add(listener);
+  }
+
+  @Override
+  public void removeListener(OnScrubListener listener) {
+    listeners.remove(listener);
   }
 
   @Override
@@ -421,7 +428,7 @@ public class DefaultTimeBar extends View implements TimeBar {
             positionScrubber(x);
           }
           scrubPosition = getScrubberPosition();
-          if (listener != null) {
+          for (OnScrubListener listener : listeners) {
             listener.onScrubMove(this, scrubPosition);
           }
           update();
@@ -584,7 +591,7 @@ public class DefaultTimeBar extends View implements TimeBar {
     if (parent != null) {
       parent.requestDisallowInterceptTouchEvent(true);
     }
-    if (listener != null) {
+    for (OnScrubListener listener : listeners) {
       listener.onScrubStart(this, getScrubberPosition());
     }
   }
@@ -597,7 +604,7 @@ public class DefaultTimeBar extends View implements TimeBar {
       parent.requestDisallowInterceptTouchEvent(false);
     }
     invalidate();
-    if (listener != null) {
+    for (OnScrubListener listener : listeners) {
       listener.onScrubStop(this, getScrubberPosition(), canceled);
     }
   }
@@ -735,7 +742,7 @@ public class DefaultTimeBar extends View implements TimeBar {
     if (!scrubbing) {
       startScrubbing();
     }
-    if (listener != null) {
+    for (OnScrubListener listener : listeners) {
       listener.onScrubMove(this, scrubPosition);
     }
     update();

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

@@ -341,7 +341,7 @@ public class PlaybackControlView extends FrameLayout {
     positionView = findViewById(R.id.exo_position);
     timeBar = findViewById(R.id.exo_progress);
     if (timeBar != null) {
-      timeBar.setListener(componentListener);
+      timeBar.addListener(componentListener);
     }
     playButton = findViewById(R.id.exo_play);
     if (playButton != null) {

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

@@ -25,16 +25,23 @@ import android.view.View;
 public interface TimeBar {
 
   /**
-   * @see View#isEnabled()
+   * Adds a listener for scrubbing events.
+   *
+   * @param listener The listener to add.
    */
-  void setEnabled(boolean enabled);
+  void addListener(OnScrubListener listener);
 
   /**
-   * Sets the listener for the scrubbing events.
+   * Removes a listener for scrubbing events.
    *
-   * @param listener The listener for scrubbing events.
+   * @param listener The listener to remove.
+   */
+  void removeListener(OnScrubListener listener);
+
+  /**
+   * @see View#isEnabled()
    */
-  void setListener(OnScrubListener listener);
+  void setEnabled(boolean enabled);
 
   /**
    * Sets the position increment for key presses and accessibility actions, in milliseconds.