diff --git a/library/common/src/main/java/com/google/android/exoplayer2/audio/AudioAttributes.java b/library/common/src/main/java/com/google/android/exoplayer2/audio/AudioAttributes.java
index f62c6b424a..c190b42a7d 100644
--- a/library/common/src/main/java/com/google/android/exoplayer2/audio/AudioAttributes.java
+++ b/library/common/src/main/java/com/google/android/exoplayer2/audio/AudioAttributes.java
@@ -16,11 +16,14 @@
 package com.google.android.exoplayer2.audio;
 
 import android.os.Bundle;
+import androidx.annotation.IntDef;
 import androidx.annotation.Nullable;
 import androidx.annotation.RequiresApi;
 import com.google.android.exoplayer2.Bundleable;
 import com.google.android.exoplayer2.C;
 import com.google.android.exoplayer2.util.Util;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
 
 /**
  * Attributes for audio playback, which configure the underlying platform {@link
@@ -35,11 +38,6 @@ import com.google.android.exoplayer2.util.Util;
  */
 public final class AudioAttributes implements Bundleable {
 
-  private static final String FIELD_CONTENT_TYPE = "contentType";
-  private static final String FIELD_FLAGS = "flags";
-  private static final String FIELD_USAGE = "usage";
-  private static final String FIELD_ALLOWED_CAPTURE_POLICY = "allowedCapturePolicy";
-
   public static final AudioAttributes DEFAULT = new Builder().build();
 
   /**
@@ -166,31 +164,46 @@ public final class AudioAttributes implements Bundleable {
     return result;
   }
 
+  // Bundleable implementation.
+
+  @Retention(RetentionPolicy.SOURCE)
+  @IntDef({FIELD_CONTENT_TYPE, FIELD_FLAGS, FIELD_USAGE, FIELD_ALLOWED_CAPTURE_POLICY})
+  private @interface FieldNumber {}
+
+  private static final int FIELD_CONTENT_TYPE = 0;
+  private static final int FIELD_FLAGS = 1;
+  private static final int FIELD_USAGE = 2;
+  private static final int FIELD_ALLOWED_CAPTURE_POLICY = 3;
+
   @Override
   public Bundle toBundle() {
     Bundle bundle = new Bundle();
-    bundle.putInt(FIELD_CONTENT_TYPE, contentType);
-    bundle.putInt(FIELD_FLAGS, flags);
-    bundle.putInt(FIELD_USAGE, usage);
-    bundle.putInt(FIELD_ALLOWED_CAPTURE_POLICY, allowedCapturePolicy);
+    bundle.putInt(keyForField(FIELD_CONTENT_TYPE), contentType);
+    bundle.putInt(keyForField(FIELD_FLAGS), flags);
+    bundle.putInt(keyForField(FIELD_USAGE), usage);
+    bundle.putInt(keyForField(FIELD_ALLOWED_CAPTURE_POLICY), allowedCapturePolicy);
     return bundle;
   }
 
   public static final Creator<AudioAttributes> CREATOR =
       bundle -> {
         Builder builder = new Builder();
-        if (bundle.containsKey(FIELD_CONTENT_TYPE)) {
-          builder.setContentType(bundle.getInt(FIELD_CONTENT_TYPE));
+        if (bundle.containsKey(keyForField(FIELD_CONTENT_TYPE))) {
+          builder.setContentType(bundle.getInt(keyForField(FIELD_CONTENT_TYPE)));
         }
-        if (bundle.containsKey(FIELD_FLAGS)) {
-          builder.setFlags(bundle.getInt(FIELD_FLAGS));
+        if (bundle.containsKey(keyForField(FIELD_FLAGS))) {
+          builder.setFlags(bundle.getInt(keyForField(FIELD_FLAGS)));
         }
-        if (bundle.containsKey(FIELD_USAGE)) {
-          builder.setUsage(bundle.getInt(FIELD_USAGE));
+        if (bundle.containsKey(keyForField(FIELD_USAGE))) {
+          builder.setUsage(bundle.getInt(keyForField(FIELD_USAGE)));
         }
-        if (bundle.containsKey(FIELD_ALLOWED_CAPTURE_POLICY)) {
-          builder.setAllowedCapturePolicy(bundle.getInt(FIELD_ALLOWED_CAPTURE_POLICY));
+        if (bundle.containsKey(keyForField(FIELD_ALLOWED_CAPTURE_POLICY))) {
+          builder.setAllowedCapturePolicy(bundle.getInt(keyForField(FIELD_ALLOWED_CAPTURE_POLICY)));
         }
         return builder.build();
       };
+
+  private static String keyForField(@FieldNumber int field) {
+    return Integer.toString(field, Character.MAX_RADIX);
+  }
 }
diff --git a/library/common/src/main/java/com/google/android/exoplayer2/device/DeviceInfo.java b/library/common/src/main/java/com/google/android/exoplayer2/device/DeviceInfo.java
index 6e01704884..bb0386314f 100644
--- a/library/common/src/main/java/com/google/android/exoplayer2/device/DeviceInfo.java
+++ b/library/common/src/main/java/com/google/android/exoplayer2/device/DeviceInfo.java
@@ -28,10 +28,6 @@ import java.lang.annotation.Target;
 /** Information about the playback device. */
 public final class DeviceInfo implements Bundleable {
 
-  private static final String FIELD_PLAYBACK_TYPE = "playbackType";
-  private static final String FIELD_MIN_VOLUME = "minVolume";
-  private static final String FIELD_MAX_VOLUME = "maxVolume";
-
   /** Types of playback. One of {@link #PLAYBACK_TYPE_LOCAL} or {@link #PLAYBACK_TYPE_REMOTE}. */
   @Documented
   @Retention(RetentionPolicy.SOURCE)
@@ -87,21 +83,36 @@ public final class DeviceInfo implements Bundleable {
     return result;
   }
 
+  // Bundleable implementation.
+
+  @Retention(RetentionPolicy.SOURCE)
+  @IntDef({FIELD_PLAYBACK_TYPE, FIELD_MIN_VOLUME, FIELD_MAX_VOLUME})
+  private @interface FieldNumber {}
+
+  private static final int FIELD_PLAYBACK_TYPE = 0;
+  private static final int FIELD_MIN_VOLUME = 1;
+  private static final int FIELD_MAX_VOLUME = 2;
+
   @Override
   public Bundle toBundle() {
     Bundle bundle = new Bundle();
-    bundle.putInt(FIELD_PLAYBACK_TYPE, playbackType);
-    bundle.putInt(FIELD_MIN_VOLUME, minVolume);
-    bundle.putInt(FIELD_MAX_VOLUME, maxVolume);
+    bundle.putInt(keyForField(FIELD_PLAYBACK_TYPE), playbackType);
+    bundle.putInt(keyForField(FIELD_MIN_VOLUME), minVolume);
+    bundle.putInt(keyForField(FIELD_MAX_VOLUME), maxVolume);
     return bundle;
   }
 
   public static final Creator<DeviceInfo> CREATOR =
       bundle -> {
         int playbackType =
-            bundle.getInt(FIELD_PLAYBACK_TYPE, /* defaultValue= */ PLAYBACK_TYPE_LOCAL);
-        int minVolume = bundle.getInt(FIELD_MIN_VOLUME, /* defaultValue= */ 0);
-        int maxVolume = bundle.getInt(FIELD_MAX_VOLUME, /* defaultValue= */ 0);
+            bundle.getInt(
+                keyForField(FIELD_PLAYBACK_TYPE), /* defaultValue= */ PLAYBACK_TYPE_LOCAL);
+        int minVolume = bundle.getInt(keyForField(FIELD_MIN_VOLUME), /* defaultValue= */ 0);
+        int maxVolume = bundle.getInt(keyForField(FIELD_MAX_VOLUME), /* defaultValue= */ 0);
         return new DeviceInfo(playbackType, minVolume, maxVolume);
       };
+
+  private static String keyForField(@FieldNumber int field) {
+    return Integer.toString(field, Character.MAX_RADIX);
+  }
 }