Clean up offline class names

This change is intended to resolve overloading of "Download",
where a DownloadTask could be an actual download task, or a
remove task.

Also cleaned up some documentation.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=194815058

demos/main/src/main/java/com/google/android/exoplayer2/demo/DemoDownloadService.java

@@ -18,7 +18,7 @@ package com.google.android.exoplayer2.demo;
 import android.app.Notification;
 import android.util.Pair;
 import com.google.android.exoplayer2.offline.DownloadManager;
-import com.google.android.exoplayer2.offline.DownloadManager.DownloadState;
+import com.google.android.exoplayer2.offline.DownloadManager.TaskState;
 import com.google.android.exoplayer2.offline.DownloadService;
 import com.google.android.exoplayer2.offline.DownloaderConstructorHelper;
 import com.google.android.exoplayer2.offline.ProgressiveDownloadAction;
@@ -75,21 +75,21 @@ public class DemoDownloadService extends DownloadService {
   }
 
   @Override
-  protected Notification getForegroundNotification(DownloadState[] downloadStates) {
+  protected Notification getForegroundNotification(TaskState[] taskStates) {
     return DownloadNotificationUtil.createProgressNotification(
-        downloadStates, this, R.drawable.exo_controls_play, CHANNEL_ID, null);
+        taskStates, this, R.drawable.exo_controls_play, CHANNEL_ID, null);
   }
 
   @Override
-  protected void onStateChange(DownloadState downloadState) {
-    int notificationId = FOREGROUND_NOTIFICATION_ID + 1 + downloadState.taskId;
+  protected void onTaskStateChanged(TaskState taskState) {
+    int notificationId = FOREGROUND_NOTIFICATION_ID + 1 + taskState.taskId;
     Notification downloadNotification =
         DownloadNotificationUtil.createDownloadFinishedNotification(
-            downloadState,
+            taskState,
             this,
             R.drawable.exo_controls_play,
             CHANNEL_ID,
-            downloadState.downloadAction.data,
+            taskState.action.data,
             new ErrorMessageProvider<Throwable>() {
               @Override
               public Pair<Integer, String> getErrorMessage(Throwable throwable) {

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

@@ -43,7 +43,7 @@ public abstract class DownloadAction {
     }
 
     /**
-     * Deserializes a {@link DownloadAction} from the {@code input}.
+     * Deserializes an action from the {@code input}.
      *
      * @param version Version of the data.
      * @param input DataInputStream to read data from.
@@ -55,17 +55,17 @@ public abstract class DownloadAction {
   }
 
   /**
-   * Deserializes one {@code action} which was serialized by {@link
-   * #serializeToStream(DownloadAction, OutputStream)} from the {@code input} using one of the
-   * {@link Deserializer}s which supports the type of the action.
+   * Deserializes one action that was serialized with {@link #serializeToStream(DownloadAction,
+   * OutputStream)} from the {@code input}, using the {@link Deserializer}s that supports the
+   * action's type.
    *
    * <p>The caller is responsible for closing the given {@link InputStream}.
    *
-   * @param deserializers Array of {@link Deserializer}s to deserialize a {@link DownloadAction}.
+   * @param deserializers {@link Deserializer}s for supported actions.
    * @param input Input stream to read serialized data.
-   * @return The deserialized {@link DownloadAction}.
-   * @throws IOException If there is an IO error from {@code input} or the action type isn't
-   *     supported by any of the {@code deserializers}.
+   * @return The deserialized action.
+   * @throws IOException If there is an IO error reading from {@code input}, or if the action type
+   *     isn't supported by any of the {@code deserializers}.
    */
   public static DownloadAction deserializeFromStream(
       Deserializer[] deserializers, InputStream input) throws IOException {
@@ -79,10 +79,10 @@ public abstract class DownloadAction {
    *
    * <p>The caller is responsible for closing the given {@link InputStream}.
    *
-   * @param deserializers Array of {@link Deserializer}s to deserialize a {@link DownloadAction}.
+   * @param deserializers {@link Deserializer}s for supported actions.
    * @param input Input stream to read serialized data.
    * @param version Master version of the serialization. See {@link DownloadAction#MASTER_VERSION}.
-   * @return The deserialized {@link DownloadAction}.
+   * @return The deserialized action.
    * @throws IOException If there is an IO error from {@code input}.
    * @throws DownloadException If the action type isn't supported by any of the {@code
    *     deserializers}.

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

@@ -25,7 +25,7 @@ import android.os.Looper;
 import android.support.annotation.Nullable;
 import android.support.annotation.StringRes;
 import android.util.Log;
-import com.google.android.exoplayer2.offline.DownloadManager.DownloadState;
+import com.google.android.exoplayer2.offline.DownloadManager.TaskState;
 import com.google.android.exoplayer2.scheduler.Requirements;
 import com.google.android.exoplayer2.scheduler.RequirementsWatcher;
 import com.google.android.exoplayer2.scheduler.Scheduler;
@@ -272,21 +272,25 @@ public abstract class DownloadService extends Service {
   /**
    * Returns a notification to be displayed when this service running in the foreground.
    *
-   * <p>This method is called when there is a download task state change and periodically while
-   * there is an active download. Update interval can be set using {@link #DownloadService(int,
+   * <p>This method is called when there is a task state change and periodically while there are
+   * active tasks. The periodic update interval can be set using {@link #DownloadService(int,
    * long)}.
    *
-   * <p>On API level 26 and above, it may be also called just before the service stops with an empty
-   * {@code downloadStates} array, returned notification is used to satisfy system requirements for
-   * foreground services.
+   * <p>On API level 26 and above, this method may also be called just before the service stops,
+   * with an empty {@code taskStates} array. The returned notification is used to satisfy system
+   * requirements for foreground services.
    *
-   * @param downloadStates DownloadState for all tasks.
-   * @return A notification to be displayed when this service running in the foreground.
+   * @param taskStates The states of all current tasks.
+   * @return The foreground notification to display.
    */
-  protected abstract Notification getForegroundNotification(DownloadState[] downloadStates);
+  protected abstract Notification getForegroundNotification(TaskState[] taskStates);
 
-  /** Called when the download state changes. */
-  protected void onStateChange(DownloadState downloadState) {
+  /**
+   * Called when the state of a task changes.
+   *
+   * @param taskState The state of the task.
+   */
+  protected void onTaskStateChanged(TaskState taskState) {
     // Do nothing.
   }
 
@@ -308,9 +312,9 @@ public abstract class DownloadService extends Service {
 
   private final class DownloadListener implements DownloadManager.DownloadListener {
     @Override
-    public void onStateChange(DownloadManager downloadManager, DownloadState downloadState) {
-      DownloadService.this.onStateChange(downloadState);
-      if (downloadState.state == DownloadState.STATE_STARTED) {
+    public void onTaskStateChanged(DownloadManager downloadManager, TaskState taskState) {
+      DownloadService.this.onTaskStateChanged(taskState);
+      if (taskState.state == TaskState.STATE_STARTED) {
         foregroundNotificationUpdater.startPeriodicUpdates();
       } else {
         foregroundNotificationUpdater.update();
@@ -349,8 +353,8 @@ public abstract class DownloadService extends Service {
     }
 
     public void update() {
-      DownloadState[] downloadStates = downloadManager.getDownloadStates();
-      startForeground(notificationId, getForegroundNotification(downloadStates));
+      TaskState[] taskStates = downloadManager.getAllTaskStates();
+      startForeground(notificationId, getForegroundNotification(taskStates));
       notificationDisplayed = true;
       if (periodicUpdatesStarted) {
         handler.removeCallbacks(this);

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

@@ -22,8 +22,8 @@ import android.os.ConditionVariable;
 import android.support.annotation.Nullable;
 import com.google.android.exoplayer2.C;
 import com.google.android.exoplayer2.offline.DownloadManager.DownloadListener;
-import com.google.android.exoplayer2.offline.DownloadManager.DownloadState;
-import com.google.android.exoplayer2.offline.DownloadManager.DownloadState.State;
+import com.google.android.exoplayer2.offline.DownloadManager.TaskState;
+import com.google.android.exoplayer2.offline.DownloadManager.TaskState.State;
 import com.google.android.exoplayer2.testutil.DummyMainThread;
 import com.google.android.exoplayer2.testutil.RobolectricUtil;
 import com.google.android.exoplayer2.upstream.DummyDataSource;
@@ -255,11 +255,11 @@ public class DownloadManagerTest {
     downloadAction1.post().assertDoesNotStart();
     downloadAction2.post().assertDoesNotStart();
 
-    DownloadState[] states = downloadManager.getDownloadStates();
+    TaskState[] states = downloadManager.getAllTaskStates();
     assertThat(states).hasLength(3);
-    assertThat(states[0].downloadAction).isEqualTo(removeAction);
-    assertThat(states[1].downloadAction).isEqualTo(downloadAction1);
-    assertThat(states[2].downloadAction).isEqualTo(downloadAction2);
+    assertThat(states[0].action).isEqualTo(removeAction);
+    assertThat(states[1].action).isEqualTo(downloadAction1);
+    assertThat(states[2].action).isEqualTo(downloadAction2);
   }
 
   @Test
@@ -503,11 +503,11 @@ public class DownloadManagerTest {
     }
 
     @Override
-    public void onStateChange(DownloadManager downloadManager, DownloadState downloadState) {
-      if (downloadState.state == DownloadState.STATE_ERROR && downloadError == null) {
-        downloadError = downloadState.error;
+    public void onTaskStateChanged(DownloadManager downloadManager, TaskState taskState) {
+      if (taskState.state == TaskState.STATE_ERROR && downloadError == null) {
+        downloadError = taskState.error;
       }
-      ((FakeDownloadAction) downloadState.downloadAction).onStateChange(downloadState.state);
+      ((FakeDownloadAction) taskState.action).onStateChange(taskState.state);
     }
 
     @Override
@@ -580,23 +580,23 @@ public class DownloadManagerTest {
 
     private FakeDownloadAction assertStarted() throws InterruptedException {
       downloader.assertStarted(ASSERT_TRUE_TIMEOUT);
-      return assertState(DownloadState.STATE_STARTED);
+      return assertState(TaskState.STATE_STARTED);
     }
 
     private FakeDownloadAction assertEnded() {
-      return assertState(DownloadState.STATE_ENDED);
+      return assertState(TaskState.STATE_ENDED);
     }
 
     private FakeDownloadAction assertError() {
-      return assertState(DownloadState.STATE_ERROR);
+      return assertState(TaskState.STATE_ERROR);
     }
 
     private FakeDownloadAction assertCancelled() {
-      return assertState(DownloadState.STATE_CANCELED);
+      return assertState(TaskState.STATE_CANCELED);
     }
 
     private FakeDownloadAction assertStopped() {
-      return assertState(DownloadState.STATE_QUEUED);
+      return assertState(TaskState.STATE_QUEUED);
     }
 
     private FakeDownloadAction assertState(@State int expectedState) {
@@ -619,13 +619,13 @@ public class DownloadManagerTest {
             if (i > 0) {
               sb.append(',');
             }
-            sb.append(DownloadState.getStateString(receivedStates.get(i)));
+            sb.append(TaskState.getStateString(receivedStates.get(i)));
           }
           fail(
               String.format(
                   Locale.US,
                   "expected:<%s> but was:<%s>",
-                  DownloadState.getStateString(expectedState),
+                  TaskState.getStateString(expectedState),
                   sb));
         }
       }

library/dash/src/test/java/com/google/android/exoplayer2/source/dash/offline/DownloadServiceDashTest.java

@@ -25,7 +25,7 @@ import android.content.Context;
 import android.content.Intent;
 import android.support.annotation.Nullable;
 import com.google.android.exoplayer2.offline.DownloadManager;
-import com.google.android.exoplayer2.offline.DownloadManager.DownloadState;
+import com.google.android.exoplayer2.offline.DownloadManager.TaskState;
 import com.google.android.exoplayer2.offline.DownloadService;
 import com.google.android.exoplayer2.offline.DownloaderConstructorHelper;
 import com.google.android.exoplayer2.scheduler.Requirements;
@@ -139,8 +139,7 @@ public class DownloadServiceDashTest {
                     }
 
                     @Override
-                    protected Notification getForegroundNotification(
-                        DownloadState[] downloadStates) {
+                    protected Notification getForegroundNotification(TaskState[] taskStates) {
                       return Mockito.mock(Notification.class);
                     }
 

library/dash/src/test/java/com/google/android/exoplayer2/source/dash/offline/TestDownloadListener.java

@@ -19,7 +19,6 @@ import static com.google.common.truth.Truth.assertThat;
 
 import com.google.android.exoplayer2.offline.DownloadManager;
 import com.google.android.exoplayer2.offline.DownloadManager.DownloadListener;
-import com.google.android.exoplayer2.offline.DownloadManager.DownloadState;
 import com.google.android.exoplayer2.testutil.DummyMainThread;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.TimeUnit;
@@ -40,9 +39,10 @@ import java.util.concurrent.TimeUnit;
   }
 
   @Override
-  public void onStateChange(DownloadManager downloadManager, DownloadState downloadState) {
-    if (downloadState.state == DownloadState.STATE_ERROR && downloadError == null) {
-      downloadError = downloadState.error;
+  public void onTaskStateChanged(
+      DownloadManager downloadManager, DownloadManager.TaskState taskState) {
+    if (taskState.state == DownloadManager.TaskState.STATE_ERROR && downloadError == null) {
+      downloadError = taskState.error;
     }
   }
 

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

@@ -21,7 +21,7 @@ import android.support.annotation.Nullable;
 import android.support.v4.app.NotificationCompat;
 import com.google.android.exoplayer2.C;
 import com.google.android.exoplayer2.offline.DownloadManager;
-import com.google.android.exoplayer2.offline.DownloadManager.DownloadState;
+import com.google.android.exoplayer2.offline.DownloadManager.TaskState;
 import com.google.android.exoplayer2.util.ErrorMessageProvider;
 
 /** Helper class to create notifications for downloads using {@link DownloadManager}. */
@@ -32,18 +32,18 @@ public final class DownloadNotificationUtil {
   private DownloadNotificationUtil() {}
 
   /**
-   * Returns a progress notification for the given {@link DownloadState}s.
+   * Returns a progress notification for the given {@link TaskState}s.
    *
-   * @param downloadStates States of the downloads.
+   * @param taskStates States of the downloads.
    * @param context Used to access resources.
    * @param smallIcon A small icon for the notification.
    * @param channelId The id of the notification channel to use. Only required for API level 26 and
    *     above.
    * @param message An optional message to display on the notification.
-   * @return A progress notification for the given {@link DownloadState}s.
+   * @return A progress notification for the given {@link TaskState}s.
    */
   public static @Nullable Notification createProgressNotification(
-      DownloadState[] downloadStates,
+      TaskState[] taskStates,
       Context context,
       int smallIcon,
       String channelId,
@@ -52,16 +52,15 @@ public final class DownloadNotificationUtil {
     int downloadTaskCount = 0;
     boolean allDownloadPercentagesUnknown = true;
     boolean haveDownloadedBytes = false;
-    for (DownloadState downloadState : downloadStates) {
-      if (downloadState.downloadAction.isRemoveAction
-          || downloadState.state != DownloadState.STATE_STARTED) {
+    for (TaskState taskState : taskStates) {
+      if (taskState.action.isRemoveAction || taskState.state != TaskState.STATE_STARTED) {
         continue;
       }
-      if (downloadState.downloadPercentage != C.PERCENTAGE_UNSET) {
+      if (taskState.downloadPercentage != C.PERCENTAGE_UNSET) {
         allDownloadPercentagesUnknown = false;
-        totalPercentage += downloadState.downloadPercentage;
+        totalPercentage += taskState.downloadPercentage;
       }
-      haveDownloadedBytes |= downloadState.downloadedBytes > 0;
+      haveDownloadedBytes |= taskState.downloadedBytes > 0;
       downloadTaskCount++;
     }
 
@@ -79,11 +78,11 @@ public final class DownloadNotificationUtil {
   }
 
   /**
-   * Returns a notification for a {@link DownloadState} which is in either {@link
-   * DownloadState#STATE_ENDED} or {@link DownloadState#STATE_ERROR} states. Returns null if it's
-   * some other state or it's state of a remove action.
+   * Returns a notification for a {@link TaskState} which is in either {@link TaskState#STATE_ENDED}
+   * or {@link TaskState#STATE_ERROR} states. Returns null if it's some other state or it's state of
+   * a remove action.
    *
-   * @param downloadState State of the download.
+   * @param taskState State of the download.
    * @param context Used to access resources.
    * @param smallIcon A small icon for the notifications.
    * @param channelId The id of the notification channel to use. Only required for API level 26 and
@@ -92,27 +91,26 @@ public final class DownloadNotificationUtil {
    * @param errorMessageProvider An optional {@link ErrorMessageProvider} for translating download
    *     errors into readable error messages. If not null and there is a download error then the
    *     error message is displayed instead of {@code message}.
-   * @return A notification for a {@link DownloadState} which is in either {@link
-   *     DownloadState#STATE_ENDED} or {@link DownloadState#STATE_ERROR} states. Returns null if
-   *     it's some other state or it's state of a remove action.
+   * @return A notification for a {@link TaskState} which is in either {@link TaskState#STATE_ENDED}
+   *     or {@link TaskState#STATE_ERROR} states. Returns null if it's some other state or it's
+   *     state of a remove action.
    */
   public static @Nullable Notification createDownloadFinishedNotification(
-      DownloadState downloadState,
+      TaskState taskState,
       Context context,
       int smallIcon,
       String channelId,
       @Nullable String message,
       @Nullable ErrorMessageProvider<Throwable> errorMessageProvider) {
-    if (downloadState.downloadAction.isRemoveAction
-        || (downloadState.state != DownloadState.STATE_ENDED
-            && downloadState.state != DownloadState.STATE_ERROR)) {
+    if (taskState.action.isRemoveAction
+        || (taskState.state != TaskState.STATE_ENDED && taskState.state != TaskState.STATE_ERROR)) {
       return null;
     }
-    if (downloadState.error != null && errorMessageProvider != null) {
-      message = errorMessageProvider.getErrorMessage(downloadState.error).second;
+    if (taskState.error != null && errorMessageProvider != null) {
+      message = errorMessageProvider.getErrorMessage(taskState.error).second;
     }
     int titleStringId =
-        downloadState.state == DownloadState.STATE_ENDED
+        taskState.state == TaskState.STATE_ENDED
             ? R.string.exo_download_completed
             : R.string.exo_download_failed;
     NotificationCompat.Builder notificationBuilder =