Finalize DownloadManager interface

- Rename getAllDownloads to getCurrentDownloads to make it clear
  that it doesn't include completed and failed downloads
- Change getDownloadCount to isWaitingForRequirements, which is
  what it's used for. Added TODO to make it returns the right thing

PiperOrigin-RevId: 243257856

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

@@ -276,29 +276,22 @@ public final class DownloadManager {
     return initialized;
   }
 
-  /** Returns whether there are no active downloads. */
+  /**
+   * Returns whether the manager is currently idle. The manager is idle if all downloads are in a
+   * terminal state (i.e. completed or failed), or if no progress can be made (e.g. because the
+   * download requirements are not met).
+   */
   public boolean isIdle() {
     return activeDownloadCount == 0 && pendingMessages == 0;
   }
 
-  /** Returns the used {@link DownloadIndex}. */
-  public DownloadIndex getDownloadIndex() {
-    return downloadIndex;
-  }
-
-  /** Returns the number of downloads. */
-  public int getDownloadCount() {
-    return downloads.size();
-  }
-
-  /** Returns the states of all current downloads. */
-  public Download[] getAllDownloads() {
-    return downloads.toArray(new Download[0]);
-  }
-
-  /** Returns the requirements needed to be met to start downloads. */
-  public Requirements getRequirements() {
-    return requirementsWatcher.getRequirements();
+  /**
+   * Returns whether this manager has one or more downloads that are not progressing for the sole
+   * reason that the {@link #getRequirements() Requirements} are not met.
+   */
+  public boolean isWaitingForRequirements() {
+    // TODO: Fix this to return the right thing.
+    return !downloads.isEmpty();
   }
 
   /**
@@ -319,6 +312,11 @@ public final class DownloadManager {
     listeners.remove(listener);
   }
 
+  /** Returns the requirements needed to be met to start downloads. */
+  public Requirements getRequirements() {
+    return requirementsWatcher.getRequirements();
+  }
+
   /**
    * Sets the requirements needed to be met to start downloads.
    *
@@ -334,6 +332,20 @@ public final class DownloadManager {
     onRequirementsStateChanged(requirementsWatcher, notMetRequirements);
   }
 
+  /** Returns the used {@link DownloadIndex}. */
+  public DownloadIndex getDownloadIndex() {
+    return downloadIndex;
+  }
+
+  /**
+   * Returns current downloads. Downloads that are in terminal states (i.e. completed or failed) are
+   * not included. To query all downloads including those in terminal states, use {@link
+   * #getDownloadIndex()} instead.
+   */
+  public Download[] getCurrentDownloads() {
+    return downloads.toArray(new Download[0]);
+  }
+
   /**
    * Starts all downloads except those that are manually stopped (i.e. have a non-zero {@link
    * Download#manualStopReason}).
@@ -537,7 +549,7 @@ public final class DownloadManager {
         break;
       case MSG_SET_DOWNLOADS_STARTED:
         boolean downloadsStarted = message.arg1 != 0;
-        setDownloadsStartedInternal(downloadsStarted);
+        setDownloadsStarted(downloadsStarted);
         break;
       case MSG_SET_NOT_MET_REQUIREMENTS:
         notMetRequirements = message.arg1;
@@ -598,7 +610,7 @@ public final class DownloadManager {
     }
   }
 
-  private void setDownloadsStartedInternal(boolean downloadsStarted) {
+  private void setDownloadsStarted(boolean downloadsStarted) {
     if (this.downloadsStarted == downloadsStarted) {
       return;
     }

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

@@ -469,7 +469,7 @@ public abstract class DownloadService extends Service {
   public void onDestroy() {
     logd("onDestroy");
     DownloadManagerHelper downloadManagerHelper = downloadManagerListeners.get(getClass());
-    boolean unschedule = downloadManager.getDownloadCount() <= 0;
+    boolean unschedule = !downloadManager.isWaitingForRequirements();
     downloadManagerHelper.detachService(this, unschedule);
     if (foregroundNotificationUpdater != null) {
       foregroundNotificationUpdater.stopPeriodicUpdates();
@@ -609,7 +609,7 @@ public abstract class DownloadService extends Service {
     }
 
     public void update() {
-      Download[] downloads = downloadManager.getAllDownloads();
+      Download[] downloads = downloadManager.getCurrentDownloads();
       startForeground(notificationId, getForegroundNotification(downloads));
       notificationDisplayed = true;
       if (periodicUpdatesStarted) {

library/core/src/test/java/com/google/android/exoplayer2/offline/DownloadManagerTest.java

@@ -346,12 +346,12 @@ public class DownloadManagerTest {
     TaskWrapper task3 = new DownloadRunner(uri3).postDownloadAction().postRemoveAction().getTask();
 
     task3.assertRemoving();
-    Download[] states = downloadManager.getAllDownloads();
+    Download[] downloads = downloadManager.getCurrentDownloads();
 
-    assertThat(states).hasLength(3);
+    assertThat(downloads).hasLength(3);
     String[] taskIds = {task1.taskId, task2.taskId, task3.taskId};
-    String[] stateTaskIds = {states[0].action.id, states[1].action.id, states[2].action.id};
-    assertThat(stateTaskIds).isEqualTo(taskIds);
+    String[] downloadIds = {downloads[0].action.id, downloads[1].action.id, downloads[2].action.id};
+    assertThat(downloadIds).isEqualTo(taskIds);
   }
 
   @Test