DownloadService: No-op cleanup

Issue: #6798
PiperOrigin-RevId: 289424582

library/core/src/main/java/com/google/android/exoplayer2/offline/DownloadService.java

@@ -34,6 +34,8 @@
 import com.google.android.exoplayer2.util.Util;
 import java.util.HashMap;
 import java.util.List;
+import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
+import org.checkerframework.checker.nullness.qual.RequiresNonNull;
 
 /** A {@link Service} for downloading media. */
 public abstract class DownloadService extends Service {
@@ -166,17 +168,18 @@ public abstract class DownloadService extends Service {
 
  private static final String TAG = "DownloadService";
 
- // Keep DownloadManagerListeners for each DownloadService as long as there are downloads (and the
- // process is running). This allows DownloadService to restart when there's no scheduler.
+ // Keep a DownloadManagerHelper for each DownloadService as long as the process is running. The
+ // helper is needed to restart the DownloadService when there's no scheduler. Even when there is a
+ // scheduler, the DownloadManagerHelper is typically able to restart the DownloadService faster.
  private static final HashMap<Class<? extends DownloadService>, DownloadManagerHelper>
- downloadManagerListeners = new HashMap<>();
+ downloadManagerHelpers = new HashMap<>();
 
  @Nullable private final ForegroundNotificationUpdater foregroundNotificationUpdater;
  @Nullable private final String channelId;
  @StringRes private final int channelNameResourceId;
  @StringRes private final int channelDescriptionResourceId;
 
- @Nullable private DownloadManager downloadManager;
+ @MonotonicNonNull private DownloadManager downloadManager;
  private int lastStartId;
  private boolean startedInForeground;
  private boolean taskRemoved;
@@ -575,16 +578,17 @@ public void onCreate() {
  NotificationUtil.IMPORTANCE_LOW);
  }
  Class<? extends DownloadService> clazz = getClass();
- DownloadManagerHelper downloadManagerHelper = downloadManagerListeners.get(clazz);
+ DownloadManagerHelper downloadManagerHelper = downloadManagerHelpers.get(clazz);
  if (downloadManagerHelper == null) {
- DownloadManager downloadManager = getDownloadManager();
+ downloadManager = getDownloadManager();
  downloadManager.resumeDownloads();
  downloadManagerHelper =
  new DownloadManagerHelper(
  getApplicationContext(), downloadManager, getScheduler(), clazz);
- downloadManagerListeners.put(clazz, downloadManagerHelper);
+ downloadManagerHelpers.put(clazz, downloadManagerHelper);
+ } else {
+ downloadManager = downloadManagerHelper.downloadManager;
  }
- downloadManager = downloadManagerHelper.downloadManager;
  downloadManagerHelper.attachService(this);
  }
 
@@ -671,9 +675,8 @@ public void onTaskRemoved(Intent rootIntent) {
  public void onDestroy() {
  isDestroyed = true;
  DownloadManagerHelper downloadManagerHelper =
- Assertions.checkNotNull(downloadManagerListeners.get(getClass()));
- boolean unschedule = !downloadManagerHelper.downloadManager.isWaitingForRequirements();
- downloadManagerHelper.detachService(this, unschedule);
+ Assertions.checkNotNull(downloadManagerHelpers.get(getClass()));
+ downloadManagerHelper.detachService(this);
  if (foregroundNotificationUpdater != null) {
  foregroundNotificationUpdater.stopPeriodicUpdates();
  }
@@ -872,10 +875,9 @@ private DownloadManagerHelper(
  this.scheduler = scheduler;
  this.serviceClass = serviceClass;
  downloadManager.addListener(this);
- if (scheduler != null) {
+ if (this.scheduler != null) {
  Requirements requirements = downloadManager.getRequirements();
- setSchedulerEnabled(
- scheduler, /* enabled= */ !requirements.checkRequirements(context), requirements);
+ setSchedulerEnabled(/* enabled= */ !requirements.checkRequirements(context), requirements);
  }
  }
 
@@ -884,10 +886,10 @@ public void attachService(DownloadService downloadService) {
  this.downloadService = downloadService;
  }
 
- public void detachService(DownloadService downloadService, boolean unschedule) {
+ public void detachService(DownloadService downloadService) {
  Assertions.checkState(this.downloadService == downloadService);
  this.downloadService = null;
- if (scheduler != null && unschedule) {
+ if (scheduler != null && !downloadManager.isWaitingForRequirements()) {
  scheduler.cancel();
  }
  }
@@ -929,12 +931,12 @@ public void onRequirementsStateChanged(
  }
  }
  if (scheduler != null) {
- setSchedulerEnabled(scheduler, /* enabled= */ !requirementsMet, requirements);
+ setSchedulerEnabled(/* enabled= */ !requirementsMet, requirements);
  }
  }
 
- private void setSchedulerEnabled(
-  Scheduler scheduler, boolean enabled, Requirements requirements) {
+ @RequiresNonNull("scheduler")
+ private void setSchedulerEnabled(boolean enabled, Requirements requirements) {
  if (!enabled) {
  scheduler.cancel();
  } else {