Remove DownloadHelper subclasses and use static methods instead.

The subclasses only call specific constructor combinations and can easily
replaced by static methods.

PiperOrigin-RevId: 231385606

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

@@ -39,13 +39,9 @@ import com.google.android.exoplayer2.offline.DownloadHelper;
 import com.google.android.exoplayer2.offline.DownloadManager;
 import com.google.android.exoplayer2.offline.DownloadService;
 import com.google.android.exoplayer2.offline.DownloadState;
-import com.google.android.exoplayer2.offline.ProgressiveDownloadHelper;
 import com.google.android.exoplayer2.offline.StreamKey;
 import com.google.android.exoplayer2.scheduler.Requirements;
 import com.google.android.exoplayer2.source.TrackGroupArray;
-import com.google.android.exoplayer2.source.dash.offline.DashDownloadHelper;
-import com.google.android.exoplayer2.source.hls.offline.HlsDownloadHelper;
-import com.google.android.exoplayer2.source.smoothstreaming.offline.SsDownloadHelper;
 import com.google.android.exoplayer2.trackselection.DefaultTrackSelector;
 import com.google.android.exoplayer2.trackselection.MappingTrackSelector.MappedTrackInfo;
 import com.google.android.exoplayer2.trackselection.TrackSelection;
@@ -215,13 +211,13 @@ public class DownloadTracker implements DownloadManager.Listener {
     int type = Util.inferContentType(uri, extension);
     switch (type) {
       case C.TYPE_DASH:
-        return new DashDownloadHelper(uri, dataSourceFactory, renderersFactory);
+        return DownloadHelper.forDash(uri, dataSourceFactory, renderersFactory);
       case C.TYPE_SS:
-        return new SsDownloadHelper(uri, dataSourceFactory, renderersFactory);
+        return DownloadHelper.forSmoothStreaming(uri, dataSourceFactory, renderersFactory);
       case C.TYPE_HLS:
-        return new HlsDownloadHelper(uri, dataSourceFactory, renderersFactory);
+        return DownloadHelper.forHls(uri, dataSourceFactory, renderersFactory);
       case C.TYPE_OTHER:
-        return new ProgressiveDownloadHelper(uri);
+        return DownloadHelper.forProgressive(uri);
       default:
         throw new IllegalStateException("Unsupported type: " + type);
     }

library/core/proguard-rules.txt

@@ -44,5 +44,22 @@
   <init>(android.net.Uri, java.util.List, com.google.android.exoplayer2.offlineDownloaderConstructorHelper);
 }
 
+# Constructors accessed via reflection in DownloadHelper
+-dontnote com.google.android.exoplayer2.source.dash.DashMediaSource$Factory
+-keepclassmembers class com.google.android.exoplayer2.source.dash.DashMediaSource$Factory {
+  <init>(com.google.android.exoplayer2.upstream.DataSource$Factory);
+  DashMediaSource createMediaSource(android.net.Uri);
+}
+-dontnote com.google.android.exoplayer2.source.hls.HlsMediaSource$Factory
+-keepclassmembers class com.google.android.exoplayer2.source.hls.HlsMediaSource$Factory {
+  <init>(com.google.android.exoplayer2.upstream.DataSource$Factory);
+  HlsMediaSource createMediaSource(android.net.Uri);
+}
+-dontnote com.google.android.exoplayer2.source.smoothstreaming.SsMediaSource$Factory
+-keepclassmembers class com.google.android.exoplayer2.source.smoothstreaming.SsMediaSource$Factory {
+  <init>(com.google.android.exoplayer2.upstream.DataSource$Factory);
+  SsMediaSource createMediaSource(android.net.Uri);
+}
+
 # Don't warn about checkerframework
 -dontwarn org.checkerframework.**

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

@@ -21,6 +21,7 @@ import android.os.HandlerThread;
 import android.os.Looper;
 import android.os.Message;
 import android.support.annotation.Nullable;
+import android.util.Pair;
 import android.util.SparseIntArray;
 import com.google.android.exoplayer2.C;
 import com.google.android.exoplayer2.ExoPlaybackException;
@@ -42,11 +43,14 @@ import com.google.android.exoplayer2.trackselection.TrackSelection;
 import com.google.android.exoplayer2.trackselection.TrackSelectorResult;
 import com.google.android.exoplayer2.upstream.Allocator;
 import com.google.android.exoplayer2.upstream.BandwidthMeter;
+import com.google.android.exoplayer2.upstream.DataSource;
 import com.google.android.exoplayer2.upstream.DefaultAllocator;
 import com.google.android.exoplayer2.upstream.TransferListener;
 import com.google.android.exoplayer2.util.Assertions;
 import com.google.android.exoplayer2.util.Util;
 import java.io.IOException;
+import java.lang.reflect.Constructor;
+import java.lang.reflect.Method;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
@@ -64,9 +68,7 @@ import org.checkerframework.checker.nullness.qual.RequiresNonNull;
  * <p>A typical usage of DownloadHelper follows these steps:
  *
  * <ol>
- *   <li>Construct the download helper with the {@link MediaSource}, information about the {@link
- *       RenderersFactory renderers} and {@link DefaultTrackSelector.Parameters parameters} for
- *       track selection.
+ *   <li>Build the helper using one of the {@code forXXX} methods.
  *   <li>Prepare the helper using {@link #prepare(Callback)} and wait for the callback.
  *   <li>Optional: Inspect the selected tracks using {@link #getMappedTrackInfo(int)} and {@link
  *       #getTrackSelections(int, int)}, and make adjustments using {@link
@@ -76,7 +78,7 @@ import org.checkerframework.checker.nullness.qual.RequiresNonNull;
  *   <li>Release the helper using {@link #release()}.
  * </ol>
  */
-public abstract class DownloadHelper {
+public final class DownloadHelper {
 
   /**
    * The default parameters used for track selection for downloading. This default selects the
@@ -104,6 +106,207 @@ public abstract class DownloadHelper {
     void onPrepareError(DownloadHelper helper, IOException e);
   }
 
+  @Nullable private static final Constructor<?> DASH_FACTORY_CONSTRUCTOR;
+  @Nullable private static final Constructor<?> HLS_FACTORY_CONSTRUCTOR;
+  @Nullable private static final Constructor<?> SS_FACTORY_CONSTRUCTOR;
+  @Nullable private static final Method DASH_FACTORY_CREATE_METHOD;
+  @Nullable private static final Method HLS_FACTORY_CREATE_METHOD;
+  @Nullable private static final Method SS_FACTORY_CREATE_METHOD;
+
+  static {
+    Pair<@NullableType Constructor<?>, @NullableType Method> dashFactoryMethods =
+        getMediaSourceFactoryMethods(
+            "com.google.android.exoplayer2.source.dash.DashMediaSource$Factory");
+    DASH_FACTORY_CONSTRUCTOR = dashFactoryMethods.first;
+    DASH_FACTORY_CREATE_METHOD = dashFactoryMethods.second;
+    Pair<@NullableType Constructor<?>, @NullableType Method> hlsFactoryMethods =
+        getMediaSourceFactoryMethods(
+            "com.google.android.exoplayer2.source.hls.HlsMediaSource$Factory");
+    HLS_FACTORY_CONSTRUCTOR = hlsFactoryMethods.first;
+    HLS_FACTORY_CREATE_METHOD = hlsFactoryMethods.second;
+    Pair<@NullableType Constructor<?>, @NullableType Method> ssFactoryMethods =
+        getMediaSourceFactoryMethods(
+            "com.google.android.exoplayer2.source.smoothstreaming.SsMediaSource$Factory");
+    SS_FACTORY_CONSTRUCTOR = ssFactoryMethods.first;
+    SS_FACTORY_CREATE_METHOD = ssFactoryMethods.second;
+  }
+
+  /**
+   * Creates a {@link DownloadHelper} for progressive streams.
+   *
+   * @param uri A stream {@link Uri}.
+   * @return A {@link DownloadHelper} for progressive streams.
+   */
+  public static DownloadHelper forProgressive(Uri uri) {
+    return forProgressive(uri, /* cacheKey= */ null);
+  }
+
+  /**
+   * Creates a {@link DownloadHelper} for progressive streams.
+   *
+   * @param uri A stream {@link Uri}.
+   * @param cacheKey An optional cache key.
+   * @return A {@link DownloadHelper} for progressive streams.
+   */
+  public static DownloadHelper forProgressive(Uri uri, @Nullable String cacheKey) {
+    return new DownloadHelper(
+        DownloadAction.TYPE_PROGRESSIVE,
+        uri,
+        cacheKey,
+        /* mediaSource= */ null,
+        DEFAULT_TRACK_SELECTOR_PARAMETERS,
+        /* rendererCapabilities= */ new RendererCapabilities[0]);
+  }
+
+  /**
+   * Creates a {@link DownloadHelper} for DASH streams.
+   *
+   * @param uri A manifest {@link Uri}.
+   * @param dataSourceFactory A {@link DataSource.Factory} used to load the manifest.
+   * @param renderersFactory A {@link RenderersFactory} creating the renderers for which tracks are
+   *     selected.
+   * @return A {@link DownloadHelper} for DASH streams.
+   * @throws IllegalStateException If the DASH module is missing.
+   */
+  public static DownloadHelper forDash(
+      Uri uri, DataSource.Factory dataSourceFactory, RenderersFactory renderersFactory) {
+    return forDash(
+        uri,
+        dataSourceFactory,
+        renderersFactory,
+        /* drmSessionManager= */ null,
+        DEFAULT_TRACK_SELECTOR_PARAMETERS);
+  }
+
+  /**
+   * Creates a {@link DownloadHelper} for DASH streams.
+   *
+   * @param uri A manifest {@link Uri}.
+   * @param dataSourceFactory A {@link DataSource.Factory} used to load the manifest.
+   * @param renderersFactory A {@link RenderersFactory} creating the renderers for which tracks are
+   *     selected.
+   * @param drmSessionManager An optional {@link DrmSessionManager} used by the renderers created by
+   *     {@code renderersFactory}.
+   * @param trackSelectorParameters {@link DefaultTrackSelector.Parameters} for selecting tracks for
+   *     downloading.
+   * @return A {@link DownloadHelper} for DASH streams.
+   * @throws IllegalStateException If the DASH module is missing.
+   */
+  public static DownloadHelper forDash(
+      Uri uri,
+      DataSource.Factory dataSourceFactory,
+      RenderersFactory renderersFactory,
+      @Nullable DrmSessionManager<FrameworkMediaCrypto> drmSessionManager,
+      DefaultTrackSelector.Parameters trackSelectorParameters) {
+    return new DownloadHelper(
+        DownloadAction.TYPE_DASH,
+        uri,
+        /* cacheKey= */ null,
+        createMediaSource(
+            uri, dataSourceFactory, DASH_FACTORY_CONSTRUCTOR, DASH_FACTORY_CREATE_METHOD),
+        trackSelectorParameters,
+        Util.getRendererCapabilities(renderersFactory, drmSessionManager));
+  }
+
+  /**
+   * Creates a {@link DownloadHelper} for HLS streams.
+   *
+   * @param uri A playlist {@link Uri}.
+   * @param dataSourceFactory A {@link DataSource.Factory} used to load the playlist.
+   * @param renderersFactory A {@link RenderersFactory} creating the renderers for which tracks are
+   *     selected.
+   * @return A {@link DownloadHelper} for HLS streams.
+   * @throws IllegalStateException If the HLS module is missing.
+   */
+  public static DownloadHelper forHls(
+      Uri uri, DataSource.Factory dataSourceFactory, RenderersFactory renderersFactory) {
+    return forHls(
+        uri,
+        dataSourceFactory,
+        renderersFactory,
+        /* drmSessionManager= */ null,
+        DEFAULT_TRACK_SELECTOR_PARAMETERS);
+  }
+
+  /**
+   * Creates a {@link DownloadHelper} for HLS streams.
+   *
+   * @param uri A playlist {@link Uri}.
+   * @param dataSourceFactory A {@link DataSource.Factory} used to load the playlist.
+   * @param renderersFactory A {@link RenderersFactory} creating the renderers for which tracks are
+   *     selected.
+   * @param drmSessionManager An optional {@link DrmSessionManager} used by the renderers created by
+   *     {@code renderersFactory}.
+   * @param trackSelectorParameters {@link DefaultTrackSelector.Parameters} for selecting tracks for
+   *     downloading.
+   * @return A {@link DownloadHelper} for HLS streams.
+   * @throws IllegalStateException If the HLS module is missing.
+   */
+  public static DownloadHelper forHls(
+      Uri uri,
+      DataSource.Factory dataSourceFactory,
+      RenderersFactory renderersFactory,
+      @Nullable DrmSessionManager<FrameworkMediaCrypto> drmSessionManager,
+      DefaultTrackSelector.Parameters trackSelectorParameters) {
+    return new DownloadHelper(
+        DownloadAction.TYPE_HLS,
+        uri,
+        /* cacheKey= */ null,
+        createMediaSource(
+            uri, dataSourceFactory, HLS_FACTORY_CONSTRUCTOR, HLS_FACTORY_CREATE_METHOD),
+        trackSelectorParameters,
+        Util.getRendererCapabilities(renderersFactory, drmSessionManager));
+  }
+
+  /**
+   * Creates a {@link DownloadHelper} for SmoothStreaming streams.
+   *
+   * @param uri A manifest {@link Uri}.
+   * @param dataSourceFactory A {@link DataSource.Factory} used to load the manifest.
+   * @param renderersFactory A {@link RenderersFactory} creating the renderers for which tracks are
+   *     selected.
+   * @return A {@link DownloadHelper} for SmoothStreaming streams.
+   * @throws IllegalStateException If the SmoothStreaming module is missing.
+   */
+  public static DownloadHelper forSmoothStreaming(
+      Uri uri, DataSource.Factory dataSourceFactory, RenderersFactory renderersFactory) {
+    return forSmoothStreaming(
+        uri,
+        dataSourceFactory,
+        renderersFactory,
+        /* drmSessionManager= */ null,
+        DEFAULT_TRACK_SELECTOR_PARAMETERS);
+  }
+
+  /**
+   * Creates a {@link DownloadHelper} for SmoothStreaming streams.
+   *
+   * @param uri A manifest {@link Uri}.
+   * @param dataSourceFactory A {@link DataSource.Factory} used to load the manifest.
+   * @param renderersFactory A {@link RenderersFactory} creating the renderers for which tracks are
+   *     selected.
+   * @param drmSessionManager An optional {@link DrmSessionManager} used by the renderers created by
+   *     {@code renderersFactory}.
+   * @param trackSelectorParameters {@link DefaultTrackSelector.Parameters} for selecting tracks for
+   *     downloading.
+   * @return A {@link DownloadHelper} for SmoothStreaming streams.
+   * @throws IllegalStateException If the SmoothStreaming module is missing.
+   */
+  public static DownloadHelper forSmoothStreaming(
+      Uri uri,
+      DataSource.Factory dataSourceFactory,
+      RenderersFactory renderersFactory,
+      @Nullable DrmSessionManager<FrameworkMediaCrypto> drmSessionManager,
+      DefaultTrackSelector.Parameters trackSelectorParameters) {
+    return new DownloadHelper(
+        DownloadAction.TYPE_SS,
+        uri,
+        /* cacheKey= */ null,
+        createMediaSource(uri, dataSourceFactory, SS_FACTORY_CONSTRUCTOR, SS_FACTORY_CREATE_METHOD),
+        trackSelectorParameters,
+        Util.getRendererCapabilities(renderersFactory, drmSessionManager));
+  }
+
   private final String downloadType;
   private final Uri uri;
   @Nullable private final String cacheKey;
@@ -131,10 +334,8 @@ public abstract class DownloadHelper {
    *     selection needs to be made.
    * @param trackSelectorParameters {@link DefaultTrackSelector.Parameters} for selecting tracks for
    *     downloading.
-   * @param renderersFactory The {@link RenderersFactory} creating the renderers for which tracks
-   *     are selected, or null if no track selection needs to be made.
-   * @param drmSessionManager An optional {@link DrmSessionManager} used by the renderers created by
-   *     {@code renderersFactory}.
+   * @param rendererCapabilities The {@link RendererCapabilities} of the renderers for which tracks
+   *     are selected.
    */
   public DownloadHelper(
       String downloadType,
@@ -142,17 +343,13 @@ public abstract class DownloadHelper {
       @Nullable String cacheKey,
       @Nullable MediaSource mediaSource,
       DefaultTrackSelector.Parameters trackSelectorParameters,
-      @Nullable RenderersFactory renderersFactory,
-      @Nullable DrmSessionManager<FrameworkMediaCrypto> drmSessionManager) {
+      RendererCapabilities[] rendererCapabilities) {
     this.downloadType = downloadType;
     this.uri = uri;
     this.cacheKey = cacheKey;
     this.mediaSource = mediaSource;
     this.trackSelector = new DefaultTrackSelector(new DownloadTrackSelection.Factory());
-    this.rendererCapabilities =
-        renderersFactory == null
-            ? new RendererCapabilities[0]
-            : Util.getRendererCapabilities(renderersFactory, drmSessionManager);
+    this.rendererCapabilities = rendererCapabilities;
     this.scratchSet = new SparseIntArray();
     trackSelector.setParameters(trackSelectorParameters);
     trackSelector.init(/* listener= */ () -> {}, new DummyBandwidthMeter());
@@ -166,7 +363,7 @@ public abstract class DownloadHelper {
    *     Looper}, in which case it will be called on the application's main thread.
    * @throws IllegalStateException If the download helper has already been prepared.
    */
-  public final void prepare(Callback callback) {
+  public void prepare(Callback callback) {
     Assertions.checkState(this.callback == null);
     this.callback = callback;
     callbackHandler =
@@ -179,7 +376,7 @@ public abstract class DownloadHelper {
   }
 
   /** Releases the helper and all resources it is holding. */
-  public final void release() {
+  public void release() {
     if (mediaPreparer != null) {
       mediaPreparer.release();
     }
@@ -190,7 +387,7 @@ public abstract class DownloadHelper {
    * preparation completes.
    */
   @Nullable
-  public final Object getManifest() {
+  public Object getManifest() {
     if (mediaSource == null) {
       return null;
     }
@@ -202,7 +399,7 @@ public abstract class DownloadHelper {
    * Returns the number of periods for which media is available. Must not be called until after
    * preparation completes.
    */
-  public final int getPeriodCount() {
+  public int getPeriodCount() {
     if (mediaSource == null) {
       return 0;
     }
@@ -220,7 +417,7 @@ public abstract class DownloadHelper {
    * @return The track groups for the period. May be {@link TrackGroupArray#EMPTY} for single stream
    *     content.
    */
-  public final TrackGroupArray getTrackGroups(int periodIndex) {
+  public TrackGroupArray getTrackGroups(int periodIndex) {
     assertPreparedWithMedia();
     return trackGroupArrays[periodIndex];
   }
@@ -232,7 +429,7 @@ public abstract class DownloadHelper {
    * @param periodIndex The period index.
    * @return The {@link MappedTrackInfo} for the period.
    */
-  public final MappedTrackInfo getMappedTrackInfo(int periodIndex) {
+  public MappedTrackInfo getMappedTrackInfo(int periodIndex) {
     assertPreparedWithMedia();
     return mappedTrackInfos[periodIndex];
   }
@@ -245,7 +442,7 @@ public abstract class DownloadHelper {
    * @param rendererIndex The renderer index.
    * @return A list of selected {@link TrackSelection track selections}.
    */
-  public final List<TrackSelection> getTrackSelections(int periodIndex, int rendererIndex) {
+  public List<TrackSelection> getTrackSelections(int periodIndex, int rendererIndex) {
     assertPreparedWithMedia();
     return immutableTrackSelectionsByPeriodAndRenderer[periodIndex][rendererIndex];
   }
@@ -256,7 +453,7 @@ public abstract class DownloadHelper {
    *
    * @param periodIndex The period index for which track selections are cleared.
    */
-  public final void clearTrackSelections(int periodIndex) {
+  public void clearTrackSelections(int periodIndex) {
     assertPreparedWithMedia();
     for (int i = 0; i < rendererCapabilities.length; i++) {
       trackSelectionsByPeriodAndRenderer[periodIndex][i].clear();
@@ -271,7 +468,7 @@ public abstract class DownloadHelper {
    * @param trackSelectorParameters The {@link DefaultTrackSelector.Parameters} to obtain the new
    *     selection of tracks.
    */
-  public final void replaceTrackSelections(
+  public void replaceTrackSelections(
       int periodIndex, DefaultTrackSelector.Parameters trackSelectorParameters) {
     clearTrackSelections(periodIndex);
     addTrackSelection(periodIndex, trackSelectorParameters);
@@ -285,7 +482,7 @@ public abstract class DownloadHelper {
    * @param trackSelectorParameters The {@link DefaultTrackSelector.Parameters} to obtain the new
    *     selection of tracks.
    */
-  public final void addTrackSelection(
+  public void addTrackSelection(
       int periodIndex, DefaultTrackSelector.Parameters trackSelectorParameters) {
     assertPreparedWithMedia();
     trackSelector.setParameters(trackSelectorParameters);
@@ -299,7 +496,7 @@ public abstract class DownloadHelper {
    * @param data Application provided data to store in {@link DownloadAction#data}.
    * @return The built {@link DownloadAction}.
    */
-  public final DownloadAction getDownloadAction(@Nullable byte[] data) {
+  public DownloadAction getDownloadAction(@Nullable byte[] data) {
     if (mediaSource == null) {
       return DownloadAction.createDownloadAction(
           downloadType, uri, /* keys= */ Collections.emptyList(), cacheKey, data);
@@ -324,7 +521,7 @@ public abstract class DownloadHelper {
    *
    * @return The built {@link DownloadAction}.
    */
-  public final DownloadAction getRemoveAction() {
+  public DownloadAction getRemoveAction() {
     return DownloadAction.createRemoveAction(downloadType, uri, cacheKey);
   }
 
@@ -452,6 +649,38 @@ public abstract class DownloadHelper {
     }
   }
 
+  private static Pair<@NullableType Constructor<?>, @NullableType Method>
+      getMediaSourceFactoryMethods(String className) {
+    Constructor<?> constructor = null;
+    Method createMethod = null;
+    try {
+      // LINT.IfChange
+      Class<?> factoryClazz = Class.forName(className);
+      constructor = factoryClazz.getConstructor(DataSource.Factory.class);
+      createMethod = factoryClazz.getMethod("createMediaSource", Uri.class);
+      // LINT.ThenChange(../../../../../../../../proguard-rules.txt)
+    } catch (Exception e) {
+      // Expected if the app was built without the respective module.
+    }
+    return Pair.create(constructor, createMethod);
+  }
+
+  private static MediaSource createMediaSource(
+      Uri uri,
+      DataSource.Factory dataSourceFactory,
+      @Nullable Constructor<?> factoryConstructor,
+      @Nullable Method createMediaSourceMethod) {
+    if (factoryConstructor == null || createMediaSourceMethod == null) {
+      throw new IllegalStateException("Module missing to create media source.");
+    }
+    try {
+      Object factory = factoryConstructor.newInstance(dataSourceFactory);
+      return (MediaSource) Assertions.checkNotNull(createMediaSourceMethod.invoke(factory, uri));
+    } catch (Exception e) {
+      throw new IllegalStateException("Failed to instantiate media source.", e);
+    }
+  }
+
   private static final class MediaPreparer
       implements MediaSource.SourceInfoRefreshListener, MediaPeriod.Callback, Handler.Callback {
 

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

@@ -1,49 +0,0 @@
-/*
- * Copyright (C) 2018 The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-package com.google.android.exoplayer2.offline;
-
-import android.net.Uri;
-import android.support.annotation.Nullable;
-
-/** A {@link DownloadHelper} for progressive streams. */
-public final class ProgressiveDownloadHelper extends DownloadHelper {
-
-  /**
-   * Creates download helper for progressive streams.
-   *
-   * @param uri The stream {@link Uri}.
-   */
-  public ProgressiveDownloadHelper(Uri uri) {
-    this(uri, /* cacheKey= */ null);
-  }
-
-  /**
-   * Creates download helper for progressive streams.
-   *
-   * @param uri The stream {@link Uri}.
-   * @param cacheKey An optional cache key.
-   */
-  public ProgressiveDownloadHelper(Uri uri, @Nullable String cacheKey) {
-    super(
-        DownloadAction.TYPE_PROGRESSIVE,
-        uri,
-        cacheKey,
-        /* mediaSource= */ null,
-        /* trackSelectorParameters= */ DownloadHelper.DEFAULT_TRACK_SELECTOR_PARAMETERS,
-        /* renderersFactory= */ null,
-        /* drmSessionManager= */ null);
-  }
-}

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

@@ -42,6 +42,7 @@ import com.google.android.exoplayer2.trackselection.TrackSelection;
 import com.google.android.exoplayer2.upstream.Allocator;
 import com.google.android.exoplayer2.util.ConditionVariable;
 import com.google.android.exoplayer2.util.MimeTypes;
+import com.google.android.exoplayer2.util.Util;
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.Arrays;
@@ -93,7 +94,7 @@ public class DownloadHelperTest {
 
   private Uri testUri;
 
-  private FakeDownloadHelper downloadHelper;
+  private DownloadHelper downloadHelper;
 
   @Before
   public void setUp() {
@@ -106,7 +107,14 @@ public class DownloadHelperTest {
         (handler, videoListener, audioListener, metadata, text, drm) ->
             new Renderer[] {textRenderer, audioRenderer, videoRenderer};
 
-    downloadHelper = new FakeDownloadHelper(testUri, renderersFactory);
+    downloadHelper =
+        new DownloadHelper(
+            TEST_DOWNLOAD_TYPE,
+            testUri,
+            TEST_CACHE_KEY,
+            new TestMediaSource(),
+            DownloadHelper.DEFAULT_TRACK_SELECTOR_PARAMETERS,
+            Util.getRendererCapabilities(renderersFactory, /* drmSessionManager= */ null));
   }
 
   @Test
@@ -346,7 +354,7 @@ public class DownloadHelperTest {
     assertThat(removeAction.isRemoveAction).isTrue();
   }
 
-  private static void prepareDownloadHelper(FakeDownloadHelper downloadHelper) throws Exception {
+  private static void prepareDownloadHelper(DownloadHelper downloadHelper) throws Exception {
     AtomicReference<Exception> prepareException = new AtomicReference<>(null);
     ConditionVariable preparedCondition = new ConditionVariable();
     downloadHelper.prepare(
@@ -426,20 +434,6 @@ public class DownloadHelperTest {
     assertThat(selectedTracksInGroup).isEqualTo(tracks);
   }
 
-  private static final class FakeDownloadHelper extends DownloadHelper {
-
-    public FakeDownloadHelper(Uri testUri, RenderersFactory renderersFactory) {
-      super(
-          TEST_DOWNLOAD_TYPE,
-          testUri,
-          TEST_CACHE_KEY,
-          new TestMediaSource(),
-          DownloadHelper.DEFAULT_TRACK_SELECTOR_PARAMETERS,
-          renderersFactory,
-          /* drmSessionManager= */ null);
-    }
-  }
-
   private static final class TestMediaSource extends FakeMediaSource {
 
     public TestMediaSource() {

library/dash/src/main/java/com/google/android/exoplayer2/source/dash/offline/DashDownloadHelper.java

@@ -1,80 +0,0 @@
-/*
- * Copyright (C) 2018 The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-package com.google.android.exoplayer2.source.dash.offline;
-
-import android.net.Uri;
-import android.support.annotation.Nullable;
-import com.google.android.exoplayer2.RenderersFactory;
-import com.google.android.exoplayer2.drm.DrmSessionManager;
-import com.google.android.exoplayer2.drm.FrameworkMediaCrypto;
-import com.google.android.exoplayer2.offline.DownloadAction;
-import com.google.android.exoplayer2.offline.DownloadHelper;
-import com.google.android.exoplayer2.source.dash.DashMediaSource;
-import com.google.android.exoplayer2.trackselection.DefaultTrackSelector;
-import com.google.android.exoplayer2.upstream.DataSource;
-
-/** A {@link DownloadHelper} for DASH streams. */
-public final class DashDownloadHelper extends DownloadHelper {
-
-  /**
-   * Creates a DASH download helper.
-   *
-   * <p>The helper uses {@link DownloadHelper#DEFAULT_TRACK_SELECTOR_PARAMETERS} for track selection
-   * and does not support drm protected content.
-   *
-   * @param uri A manifest {@link Uri}.
-   * @param manifestDataSourceFactory A {@link DataSource.Factory} used to load the manifest.
-   * @param renderersFactory The {@link RenderersFactory} creating the renderers for which tracks
-   *     are selected.
-   */
-  public DashDownloadHelper(
-      Uri uri, DataSource.Factory manifestDataSourceFactory, RenderersFactory renderersFactory) {
-    this(
-        uri,
-        manifestDataSourceFactory,
-        DownloadHelper.DEFAULT_TRACK_SELECTOR_PARAMETERS,
-        renderersFactory,
-        /* drmSessionManager= */ null);
-  }
-
-  /**
-   * Creates a DASH download helper.
-   *
-   * @param uri A manifest {@link Uri}.
-   * @param manifestDataSourceFactory A {@link DataSource.Factory} used to load the manifest.
-   * @param trackSelectorParameters {@link DefaultTrackSelector.Parameters} for selecting tracks for
-   *     downloading.
-   * @param renderersFactory The {@link RenderersFactory} creating the renderers for which tracks
-   *     are selected.
-   * @param drmSessionManager An optional {@link DrmSessionManager} used by the renderers created by
-   *     {@code renderersFactory}.
-   */
-  public DashDownloadHelper(
-      Uri uri,
-      DataSource.Factory manifestDataSourceFactory,
-      DefaultTrackSelector.Parameters trackSelectorParameters,
-      RenderersFactory renderersFactory,
-      @Nullable DrmSessionManager<FrameworkMediaCrypto> drmSessionManager) {
-    super(
-        DownloadAction.TYPE_DASH,
-        uri,
-        /* cacheKey= */ null,
-        new DashMediaSource.Factory(manifestDataSourceFactory).createMediaSource(uri),
-        trackSelectorParameters,
-        renderersFactory,
-        drmSessionManager);
-  }
-}

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

@@ -0,0 +1,43 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.google.android.exoplayer2.source.dash.offline;
+
+import android.net.Uri;
+import com.google.android.exoplayer2.Renderer;
+import com.google.android.exoplayer2.offline.DownloadHelper;
+import com.google.android.exoplayer2.testutil.FakeDataSource;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.robolectric.RobolectricTestRunner;
+
+/** Unit test to verify creation of a DASH {@link DownloadHelper}. */
+@RunWith(RobolectricTestRunner.class)
+public final class DownloadHelperTest {
+
+  @Test
+  public void staticDownloadHelperForDash_doesNotThrow() {
+    DownloadHelper.forDash(
+        Uri.parse("http://uri"),
+        new FakeDataSource.Factory(),
+        (handler, videoListener, audioListener, text, metadata, drm) -> new Renderer[0]);
+    DownloadHelper.forDash(
+        Uri.parse("http://uri"),
+        new FakeDataSource.Factory(),
+        (handler, videoListener, audioListener, text, metadata, drm) -> new Renderer[0],
+        /* drmSessionManager= */ null,
+        DownloadHelper.DEFAULT_TRACK_SELECTOR_PARAMETERS);
+  }
+}

library/hls/src/main/java/com/google/android/exoplayer2/source/hls/offline/HlsDownloadHelper.java

@@ -1,82 +0,0 @@
-/*
- * Copyright (C) 2018 The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-package com.google.android.exoplayer2.source.hls.offline;
-
-import android.net.Uri;
-import android.support.annotation.Nullable;
-import com.google.android.exoplayer2.RenderersFactory;
-import com.google.android.exoplayer2.drm.DrmSessionManager;
-import com.google.android.exoplayer2.drm.FrameworkMediaCrypto;
-import com.google.android.exoplayer2.offline.DownloadAction;
-import com.google.android.exoplayer2.offline.DownloadHelper;
-import com.google.android.exoplayer2.source.hls.HlsMediaSource;
-import com.google.android.exoplayer2.trackselection.DefaultTrackSelector;
-import com.google.android.exoplayer2.upstream.DataSource;
-
-/** A {@link DownloadHelper} for HLS streams. */
-public final class HlsDownloadHelper extends DownloadHelper {
-
-  /**
-   * Creates a HLS download helper.
-   *
-   * <p>The helper uses {@link DownloadHelper#DEFAULT_TRACK_SELECTOR_PARAMETERS} for track selection
-   * and does not support drm protected content.
-   *
-   * @param uri A manifest {@link Uri}.
-   * @param manifestDataSourceFactory A {@link DataSource.Factory} used to load the manifest.
-   * @param renderersFactory The {@link RenderersFactory} creating the renderers for which tracks
-   *     are selected.
-   */
-  public HlsDownloadHelper(
-      Uri uri, DataSource.Factory manifestDataSourceFactory, RenderersFactory renderersFactory) {
-    this(
-        uri,
-        manifestDataSourceFactory,
-        DownloadHelper.DEFAULT_TRACK_SELECTOR_PARAMETERS,
-        renderersFactory,
-        /* drmSessionManager= */ null);
-  }
-
-  /**
-   * Creates a HLS download helper.
-   *
-   * @param uri A manifest {@link Uri}.
-   * @param manifestDataSourceFactory A {@link DataSource.Factory} used to load the manifest.
-   * @param trackSelectorParameters {@link DefaultTrackSelector.Parameters} for selecting tracks for
-   *     downloading.
-   * @param renderersFactory The {@link RenderersFactory} creating the renderers for which tracks
-   *     are selected.
-   * @param drmSessionManager An optional {@link DrmSessionManager} used by the renderers created by
-   *     {@code renderersFactory}.
-   */
-  public HlsDownloadHelper(
-      Uri uri,
-      DataSource.Factory manifestDataSourceFactory,
-      DefaultTrackSelector.Parameters trackSelectorParameters,
-      RenderersFactory renderersFactory,
-      @Nullable DrmSessionManager<FrameworkMediaCrypto> drmSessionManager) {
-    super(
-        DownloadAction.TYPE_HLS,
-        uri,
-        /* cacheKey= */ null,
-        new HlsMediaSource.Factory(manifestDataSourceFactory)
-            .setAllowChunklessPreparation(true)
-            .createMediaSource(uri),
-        trackSelectorParameters,
-        renderersFactory,
-        drmSessionManager);
-  }
-}

library/hls/src/test/java/com/google/android/exoplayer2/source/hls/offline/DownloadHelperTest.java

@@ -0,0 +1,43 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.google.android.exoplayer2.source.hls.offline;
+
+import android.net.Uri;
+import com.google.android.exoplayer2.Renderer;
+import com.google.android.exoplayer2.offline.DownloadHelper;
+import com.google.android.exoplayer2.testutil.FakeDataSource;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.robolectric.RobolectricTestRunner;
+
+/** Unit test to verify creation of a HLS {@link DownloadHelper}. */
+@RunWith(RobolectricTestRunner.class)
+public final class DownloadHelperTest {
+
+  @Test
+  public void staticDownloadHelperForHls_doesNotThrow() {
+    DownloadHelper.forHls(
+        Uri.parse("http://uri"),
+        new FakeDataSource.Factory(),
+        (handler, videoListener, audioListener, text, metadata, drm) -> new Renderer[0]);
+    DownloadHelper.forHls(
+        Uri.parse("http://uri"),
+        new FakeDataSource.Factory(),
+        (handler, videoListener, audioListener, text, metadata, drm) -> new Renderer[0],
+        /* drmSessionManager= */ null,
+        DownloadHelper.DEFAULT_TRACK_SELECTOR_PARAMETERS);
+  }
+}

library/smoothstreaming/src/main/java/com/google/android/exoplayer2/source/smoothstreaming/offline/SsDownloadHelper.java

@@ -1,80 +0,0 @@
-/*
- * Copyright (C) 2018 The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-package com.google.android.exoplayer2.source.smoothstreaming.offline;
-
-import android.net.Uri;
-import android.support.annotation.Nullable;
-import com.google.android.exoplayer2.RenderersFactory;
-import com.google.android.exoplayer2.drm.DrmSessionManager;
-import com.google.android.exoplayer2.drm.FrameworkMediaCrypto;
-import com.google.android.exoplayer2.offline.DownloadAction;
-import com.google.android.exoplayer2.offline.DownloadHelper;
-import com.google.android.exoplayer2.source.smoothstreaming.SsMediaSource;
-import com.google.android.exoplayer2.trackselection.DefaultTrackSelector;
-import com.google.android.exoplayer2.upstream.DataSource;
-
-/** A {@link DownloadHelper} for SmoothStreaming streams. */
-public final class SsDownloadHelper extends DownloadHelper {
-
-  /**
-   * Creates a SmoothStreaming download helper.
-   *
-   * <p>The helper uses {@link DownloadHelper#DEFAULT_TRACK_SELECTOR_PARAMETERS} for track selection
-   * and does not support drm protected content.
-   *
-   * @param uri A manifest {@link Uri}.
-   * @param manifestDataSourceFactory A {@link DataSource.Factory} used to load the manifest.
-   * @param renderersFactory The {@link RenderersFactory} creating the renderers for which tracks
-   *     are selected.
-   */
-  public SsDownloadHelper(
-      Uri uri, DataSource.Factory manifestDataSourceFactory, RenderersFactory renderersFactory) {
-    this(
-        uri,
-        manifestDataSourceFactory,
-        DownloadHelper.DEFAULT_TRACK_SELECTOR_PARAMETERS,
-        renderersFactory,
-        /* drmSessionManager= */ null);
-  }
-
-  /**
-   * Creates a SmoothStreaming download helper.
-   *
-   * @param uri A manifest {@link Uri}.
-   * @param manifestDataSourceFactory A {@link DataSource.Factory} used to load the manifest.
-   * @param trackSelectorParameters {@link DefaultTrackSelector.Parameters} for selecting tracks for
-   *     downloading.
-   * @param renderersFactory The {@link RenderersFactory} creating the renderers for which tracks
-   *     are selected.
-   * @param drmSessionManager An optional {@link DrmSessionManager} used by the renderers created by
-   *     {@code renderersFactory}.
-   */
-  public SsDownloadHelper(
-      Uri uri,
-      DataSource.Factory manifestDataSourceFactory,
-      DefaultTrackSelector.Parameters trackSelectorParameters,
-      RenderersFactory renderersFactory,
-      @Nullable DrmSessionManager<FrameworkMediaCrypto> drmSessionManager) {
-    super(
-        DownloadAction.TYPE_SS,
-        uri,
-        /* cacheKey= */ null,
-        new SsMediaSource.Factory(manifestDataSourceFactory).createMediaSource(uri),
-        trackSelectorParameters,
-        renderersFactory,
-        drmSessionManager);
-  }
-}

library/smoothstreaming/src/test/java/com/google/android/exoplayer2/source/smoothstreaming/offline/DownloadHelperTest.java

@@ -0,0 +1,43 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.google.android.exoplayer2.source.smoothstreaming.offline;
+
+import android.net.Uri;
+import com.google.android.exoplayer2.Renderer;
+import com.google.android.exoplayer2.offline.DownloadHelper;
+import com.google.android.exoplayer2.testutil.FakeDataSource;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.robolectric.RobolectricTestRunner;
+
+/** Unit test to verify creation of a SmoothStreaming {@link DownloadHelper}. */
+@RunWith(RobolectricTestRunner.class)
+public final class DownloadHelperTest {
+
+  @Test
+  public void staticDownloadHelperForSmoothStreaming_doesNotThrow() {
+    DownloadHelper.forSmoothStreaming(
+        Uri.parse("http://uri"),
+        new FakeDataSource.Factory(),
+        (handler, videoListener, audioListener, text, metadata, drm) -> new Renderer[0]);
+    DownloadHelper.forSmoothStreaming(
+        Uri.parse("http://uri"),
+        new FakeDataSource.Factory(),
+        (handler, videoListener, audioListener, text, metadata, drm) -> new Renderer[0],
+        /* drmSessionManager= */ null,
+        DownloadHelper.DEFAULT_TRACK_SELECTOR_PARAMETERS);
+  }
+}