Allow stable API users to use DebugTextViewHelper

This is used from the main demo app.

PiperOrigin-RevId: 445420580

library/core/src/main/java/com/google/android/exoplayer2/util/DebugTextViewHelper.java

@@ -28,12 +28,13 @@ import java.util.Locale;
  * A helper class for periodically updating a {@link TextView} with debug information obtained from
  * an {@link ExoPlayer}.
  */
-public class DebugTextViewHelper implements Player.Listener, Runnable {
+public class DebugTextViewHelper {
 
   private static final int REFRESH_INTERVAL_MS = 1000;
 
   private final ExoPlayer player;
   private final TextView textView;
+  private final Updater updater;
 
   private boolean started;
 
@@ -47,6 +48,7 @@ public class DebugTextViewHelper implements Player.Listener, Runnable {
     Assertions.checkArgument(player.getApplicationLooper() == Looper.getMainLooper());
     this.player = player;
     this.textView = textView;
+    this.updater = new Updater();
   }
 
   /**
@@ -58,7 +60,7 @@ public class DebugTextViewHelper implements Player.Listener, Runnable {
       return;
     }
     started = true;
-    player.addListener(this);
+    player.addListener(updater);
     updateAndPost();
   }
 
@@ -71,36 +73,8 @@ public class DebugTextViewHelper implements Player.Listener, Runnable {
       return;
     }
     started = false;
-    player.removeListener(this);
+    player.removeListener(updater);
-    textView.removeCallbacks(this);
+    textView.removeCallbacks(updater);
-  }
-
-  // Player.Listener implementation.
-
-  @Override
-  public final void onPlaybackStateChanged(@Player.State int playbackState) {
-    updateAndPost();
-  }
-
-  @Override
-  public final void onPlayWhenReadyChanged(
-      boolean playWhenReady, @Player.PlayWhenReadyChangeReason int reason) {
-    updateAndPost();
-  }
-
-  @Override
-  public final void onPositionDiscontinuity(
-      Player.PositionInfo oldPosition,
-      Player.PositionInfo newPosition,
-      @Player.DiscontinuityReason int reason) {
-    updateAndPost();
-  }
-
-  // Runnable implementation.
-
-  @Override
-  public final void run() {
-    updateAndPost();
   }
 
   // Protected methods.
@@ -108,8 +82,8 @@ public class DebugTextViewHelper implements Player.Listener, Runnable {
   @SuppressLint("SetTextI18n")
   protected final void updateAndPost() {
     textView.setText(getDebugString());
-    textView.removeCallbacks(this);
+    textView.removeCallbacks(updater);
-    textView.postDelayed(this, REFRESH_INTERVAL_MS);
+    textView.postDelayed(updater, REFRESH_INTERVAL_MS);
   }
 
   /** Returns the debugging information string to be shown by the target {@link TextView}. */
@@ -219,4 +193,35 @@ public class DebugTextViewHelper implements Player.Listener, Runnable {
       return String.valueOf(averageUs);
     }
   }
+
+  private final class Updater implements Player.Listener, Runnable {
+
+    // Player.Listener implementation.
+
+    @Override
+    public void onPlaybackStateChanged(@Player.State int playbackState) {
+      updateAndPost();
+    }
+
+    @Override
+    public void onPlayWhenReadyChanged(
+        boolean playWhenReady, @Player.PlayWhenReadyChangeReason int reason) {
+      updateAndPost();
+    }
+
+    @Override
+    public void onPositionDiscontinuity(
+        Player.PositionInfo oldPosition,
+        Player.PositionInfo newPosition,
+        @Player.DiscontinuityReason int reason) {
+      updateAndPost();
+    }
+
+    // Runnable implementation.
+
+    @Override
+    public void run() {
+      updateAndPost();
+    }
+  }
 }