Add dependency on nullness annotations and add missing annotations for DASH.

This includes only the (hopefully) non-debatable changes for the DASH module
and all needed changes for call into the core library.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=195097791

RELEASENOTES.md

@@ -2,6 +2,7 @@
 
 ### dev-v2 (not yet released) ###
 
+* Added dependency on checkerframework annotations for static code analysis.
 * Optimize seeking in FMP4 by enabling seeking to the nearest sync sample within
   a fragment. This benefits standalone FMP4 playbacks, DASH and SmoothStreaming.
 * Moved initial bitrate estimate from `AdaptiveTrackSelection` to

constants.gradle

@@ -31,6 +31,7 @@ project.ext {
     junitVersion = '4.12'
     truthVersion = '0.39'
     robolectricVersion = '3.7.1'
+    checkerframeworkVersion = '2.5.0'
     modulePrefix = ':'
     if (gradle.ext.has('exoplayerModulePrefix')) {
         modulePrefix += gradle.ext.exoplayerModulePrefix

library/core/build.gradle

@@ -46,6 +46,7 @@ android {
 
 dependencies {
     implementation 'com.android.support:support-annotations:' + supportLibraryVersion
+    implementation 'org.checkerframework:checker-qual:' + checkerframeworkVersion
     androidTestImplementation 'com.google.dexmaker:dexmaker:' + dexmakerVersion
     androidTestImplementation 'com.google.dexmaker:dexmaker-mockito:' + dexmakerVersion
     androidTestImplementation 'com.google.truth:truth:' + truthVersion

library/core/src/main/java/com/google/android/exoplayer2/extractor/mp4/FragmentedMp4Extractor.java

@@ -121,11 +121,11 @@ public final class FragmentedMp4Extractor implements Extractor {
 
   // Workarounds.
   @Flags private final int flags;
-  private final Track sideloadedTrack;
+  private final @Nullable Track sideloadedTrack;
 
   // Sideloaded data.
   private final List<Format> closedCaptionFormats;
-  private final DrmInitData sideloadedDrmInitData;
+  private final @Nullable DrmInitData sideloadedDrmInitData;
 
   // Track-linked data bundle, accessible as a whole through trackID.
   private final SparseArray<TrackBundle> trackBundles;
@@ -136,7 +136,7 @@ public final class FragmentedMp4Extractor implements Extractor {
   private final ParsableByteArray nalBuffer;
 
   // Adjusts sample timestamps.
-  private final TimestampAdjuster timestampAdjuster;
+  private final @Nullable TimestampAdjuster timestampAdjuster;
 
   // Parser state.
   private final ParsableByteArray atomHeader;
@@ -185,20 +185,23 @@ public final class FragmentedMp4Extractor implements Extractor {
    * @param flags Flags that control the extractor's behavior.
    * @param timestampAdjuster Adjusts sample timestamps. May be null if no adjustment is needed.
    */
-  public FragmentedMp4Extractor(@Flags int flags, TimestampAdjuster timestampAdjuster) {
+  public FragmentedMp4Extractor(@Flags int flags, @Nullable TimestampAdjuster timestampAdjuster) {
     this(flags, timestampAdjuster, null, null);
   }
 
   /**
    * @param flags Flags that control the extractor's behavior.
    * @param timestampAdjuster Adjusts sample timestamps. May be null if no adjustment is needed.
-   * @param sideloadedTrack Sideloaded track information, in the case that the extractor
-   *     will not receive a moov box in the input data. Null if a moov box is expected.
+   * @param sideloadedTrack Sideloaded track information, in the case that the extractor will not
+   *     receive a moov box in the input data. Null if a moov box is expected.
    * @param sideloadedDrmInitData The {@link DrmInitData} to use for encrypted tracks. If null, the
    *     pssh boxes (if present) will be used.
    */
-  public FragmentedMp4Extractor(@Flags int flags, TimestampAdjuster timestampAdjuster,
-      Track sideloadedTrack, DrmInitData sideloadedDrmInitData) {
+  public FragmentedMp4Extractor(
+      @Flags int flags,
+      @Nullable TimestampAdjuster timestampAdjuster,
+      @Nullable Track sideloadedTrack,
+      @Nullable DrmInitData sideloadedDrmInitData) {
     this(flags, timestampAdjuster, sideloadedTrack, sideloadedDrmInitData,
         Collections.<Format>emptyList());
   }
@@ -206,15 +209,19 @@ public final class FragmentedMp4Extractor implements Extractor {
   /**
    * @param flags Flags that control the extractor's behavior.
    * @param timestampAdjuster Adjusts sample timestamps. May be null if no adjustment is needed.
-   * @param sideloadedTrack Sideloaded track information, in the case that the extractor
-   *     will not receive a moov box in the input data. Null if a moov box is expected.
+   * @param sideloadedTrack Sideloaded track information, in the case that the extractor will not
+   *     receive a moov box in the input data. Null if a moov box is expected.
    * @param sideloadedDrmInitData The {@link DrmInitData} to use for encrypted tracks. If null, the
    *     pssh boxes (if present) will be used.
    * @param closedCaptionFormats For tracks that contain SEI messages, the formats of the closed
    *     caption channels to expose.
    */
-  public FragmentedMp4Extractor(@Flags int flags, TimestampAdjuster timestampAdjuster,
-      Track sideloadedTrack, DrmInitData sideloadedDrmInitData, List<Format> closedCaptionFormats) {
+  public FragmentedMp4Extractor(
+      @Flags int flags,
+      @Nullable TimestampAdjuster timestampAdjuster,
+      @Nullable Track sideloadedTrack,
+      @Nullable DrmInitData sideloadedDrmInitData,
+      List<Format> closedCaptionFormats) {
     this(flags, timestampAdjuster, sideloadedTrack, sideloadedDrmInitData,
         closedCaptionFormats, null);
   }
@@ -222,8 +229,8 @@ public final class FragmentedMp4Extractor implements Extractor {
   /**
    * @param flags Flags that control the extractor's behavior.
    * @param timestampAdjuster Adjusts sample timestamps. May be null if no adjustment is needed.
-   * @param sideloadedTrack Sideloaded track information, in the case that the extractor
-   *     will not receive a moov box in the input data. Null if a moov box is expected.
+   * @param sideloadedTrack Sideloaded track information, in the case that the extractor will not
+   *     receive a moov box in the input data. Null if a moov box is expected.
    * @param sideloadedDrmInitData The {@link DrmInitData} to use for encrypted tracks. If null, the
    *     pssh boxes (if present) will be used.
    * @param closedCaptionFormats For tracks that contain SEI messages, the formats of the closed
@@ -232,8 +239,12 @@ public final class FragmentedMp4Extractor implements Extractor {
    *     targeting the player, even if {@link #FLAG_ENABLE_EMSG_TRACK} is not set. Null if special
    *     handling of emsg messages for players is not required.
    */
-  public FragmentedMp4Extractor(@Flags int flags, TimestampAdjuster timestampAdjuster,
-      Track sideloadedTrack, DrmInitData sideloadedDrmInitData, List<Format> closedCaptionFormats,
+  public FragmentedMp4Extractor(
+      @Flags int flags,
+      @Nullable TimestampAdjuster timestampAdjuster,
+      @Nullable Track sideloadedTrack,
+      @Nullable DrmInitData sideloadedDrmInitData,
+      List<Format> closedCaptionFormats,
       @Nullable TrackOutput additionalEmsgTrackOutput) {
     this.flags = flags | (sideloadedTrack != null ? FLAG_SIDELOADED : 0);
     this.timestampAdjuster = timestampAdjuster;

library/core/src/main/java/com/google/android/exoplayer2/extractor/mp4/PsshAtomUtil.java

@@ -15,6 +15,7 @@
  */
 package com.google.android.exoplayer2.extractor.mp4;
 
+import android.support.annotation.Nullable;
 import android.util.Log;
 import com.google.android.exoplayer2.util.ParsableByteArray;
 import java.nio.ByteBuffer;
@@ -36,7 +37,7 @@ public final class PsshAtomUtil {
    * @param data The scheme specific data.
    * @return The PSSH atom.
    */
-  public static byte[] buildPsshAtom(UUID systemId, byte[] data) {
+  public static byte[] buildPsshAtom(UUID systemId, @Nullable byte[] data) {
     return buildPsshAtom(systemId, null, data);
   }
 
@@ -48,7 +49,8 @@ public final class PsshAtomUtil {
    * @param data The scheme specific data.
    * @return The PSSH atom.
    */
-  public static byte[] buildPsshAtom(UUID systemId, UUID[] keyIds, byte[] data) {
+  public static byte[] buildPsshAtom(
+      UUID systemId, @Nullable UUID[] keyIds, @Nullable byte[] data) {
     boolean buildV1Atom = keyIds != null;
     int dataLength = data != null ? data.length : 0;
     int psshBoxLength = Atom.FULL_HEADER_SIZE + 16 /* SystemId */ + 4 /* DataSize */ + dataLength;
@@ -77,14 +79,14 @@ public final class PsshAtomUtil {
 
   /**
    * Parses the UUID from a PSSH atom. Version 0 and 1 PSSH atoms are supported.
-   * <p>
-   * The UUID is only parsed if the data is a valid PSSH atom.
+   *
+   * <p>The UUID is only parsed if the data is a valid PSSH atom.
    *
    * @param atom The atom to parse.
-   * @return The parsed UUID. Null if the input is not a valid PSSH atom, or if the PSSH atom has
-   *     an unsupported version.
+   * @return The parsed UUID. Null if the input is not a valid PSSH atom, or if the PSSH atom has an
+   *     unsupported version.
    */
-  public static UUID parseUuid(byte[] atom) {
+  public static @Nullable UUID parseUuid(byte[] atom) {
     PsshAtom parsedAtom = parsePsshAtom(atom);
     if (parsedAtom == null) {
       return null;
@@ -111,8 +113,8 @@ public final class PsshAtomUtil {
 
   /**
    * Parses the scheme specific data from a PSSH atom. Version 0 and 1 PSSH atoms are supported.
-   * <p>
-   * The scheme specific data is only parsed if the data is a valid PSSH atom matching the given
+   *
+   * <p>The scheme specific data is only parsed if the data is a valid PSSH atom matching the given
    * UUID, or if the data is a valid PSSH atom of any type in the case that the passed UUID is null.
    *
    * @param atom The atom to parse.
@@ -120,7 +122,7 @@ public final class PsshAtomUtil {
    * @return The parsed scheme specific data. Null if the input is not a valid PSSH atom, or if the
    *     PSSH atom has an unsupported version, or if the PSSH atom does not match the passed UUID.
    */
-  public static byte[] parseSchemeSpecificData(byte[] atom, UUID uuid) {
+  public static @Nullable byte[] parseSchemeSpecificData(byte[] atom, UUID uuid) {
     PsshAtom parsedAtom = parsePsshAtom(atom);
     if (parsedAtom == null) {
       return null;
@@ -140,7 +142,7 @@ public final class PsshAtomUtil {
    *     has an unsupported version.
    */
   // TODO: Support parsing of the key ids for version 1 PSSH atoms.
-  private static PsshAtom parsePsshAtom(byte[] atom) {
+  private static @Nullable PsshAtom parsePsshAtom(byte[] atom) {
     ParsableByteArray atomData = new ParsableByteArray(atom);
     if (atomData.limit() < Atom.FULL_HEADER_SIZE + 16 /* UUID */ + 4 /* DataSize */) {
       // Data too short.

library/core/src/main/java/com/google/android/exoplayer2/source/chunk/Chunk.java

@@ -15,6 +15,7 @@
  */
 package com.google.android.exoplayer2.source.chunk;
 
+import android.support.annotation.Nullable;
 import com.google.android.exoplayer2.C;
 import com.google.android.exoplayer2.Format;
 import com.google.android.exoplayer2.upstream.DataSource;
@@ -51,7 +52,7 @@ public abstract class Chunk implements Loadable {
    * Optional data associated with the selection of the track to which this chunk belongs. Null if
    * the chunk does not belong to a track.
    */
-  public final Object trackSelectionData;
+  public final @Nullable Object trackSelectionData;
   /**
    * The start time of the media contained by the chunk, or {@link C#TIME_UNSET} if the data
    * being loaded does not contain media samples.
@@ -75,8 +76,15 @@ public abstract class Chunk implements Loadable {
    * @param startTimeUs See {@link #startTimeUs}.
    * @param endTimeUs See {@link #endTimeUs}.
    */
-  public Chunk(DataSource dataSource, DataSpec dataSpec, int type, Format trackFormat,
-      int trackSelectionReason, Object trackSelectionData, long startTimeUs, long endTimeUs) {
+  public Chunk(
+      DataSource dataSource,
+      DataSpec dataSpec,
+      int type,
+      Format trackFormat,
+      int trackSelectionReason,
+      @Nullable Object trackSelectionData,
+      long startTimeUs,
+      long endTimeUs) {
     this.dataSource = Assertions.checkNotNull(dataSource);
     this.dataSpec = Assertions.checkNotNull(dataSpec);
     this.type = type;

library/core/src/main/java/com/google/android/exoplayer2/source/chunk/InitializationChunk.java

@@ -15,6 +15,7 @@
  */
 package com.google.android.exoplayer2.source.chunk;
 
+import android.support.annotation.Nullable;
 import com.google.android.exoplayer2.C;
 import com.google.android.exoplayer2.Format;
 import com.google.android.exoplayer2.extractor.DefaultExtractorInput;
@@ -44,8 +45,12 @@ public final class InitializationChunk extends Chunk {
    * @param trackSelectionData See {@link #trackSelectionData}.
    * @param extractorWrapper A wrapped extractor to use for parsing the initialization data.
    */
-  public InitializationChunk(DataSource dataSource, DataSpec dataSpec, Format trackFormat,
-      int trackSelectionReason, Object trackSelectionData,
+  public InitializationChunk(
+      DataSource dataSource,
+      DataSpec dataSpec,
+      Format trackFormat,
+      int trackSelectionReason,
+      @Nullable Object trackSelectionData,
       ChunkExtractorWrapper extractorWrapper) {
     super(dataSource, dataSpec, C.DATA_TYPE_MEDIA_INITIALIZATION, trackFormat, trackSelectionReason,
         trackSelectionData, C.TIME_UNSET, C.TIME_UNSET);

library/core/src/main/java/com/google/android/exoplayer2/util/Assertions.java

@@ -16,8 +16,10 @@
 package com.google.android.exoplayer2.util;
 
 import android.os.Looper;
+import android.support.annotation.Nullable;
 import android.text.TextUtils;
 import com.google.android.exoplayer2.ExoPlayerLibraryInfo;
+import org.checkerframework.checker.nullness.qual.EnsuresNonNull;
 
 /**
  * Provides methods for asserting the truth of expressions and properties.
@@ -102,7 +104,8 @@ public final class Assertions {
    * @return The non-null reference that was validated.
    * @throws NullPointerException If {@code reference} is null.
    */
-  public static <T> T checkNotNull(T reference) {
+  @EnsuresNonNull({"#1"})
+  public static <T> T checkNotNull(@Nullable T reference) {
     if (ExoPlayerLibraryInfo.ASSERTIONS_ENABLED && reference == null) {
       throw new NullPointerException();
     }
@@ -119,7 +122,8 @@ public final class Assertions {
    * @return The non-null reference that was validated.
    * @throws NullPointerException If {@code reference} is null.
    */
-  public static <T> T checkNotNull(T reference, Object errorMessage) {
+  @EnsuresNonNull({"#1"})
+  public static <T> T checkNotNull(@Nullable T reference, Object errorMessage) {
     if (ExoPlayerLibraryInfo.ASSERTIONS_ENABLED && reference == null) {
       throw new NullPointerException(String.valueOf(errorMessage));
     }
@@ -133,7 +137,8 @@ public final class Assertions {
    * @return The non-null, non-empty string that was validated.
    * @throws IllegalArgumentException If {@code string} is null or 0-length.
    */
-  public static String checkNotEmpty(String string) {
+  @EnsuresNonNull({"#1"})
+  public static String checkNotEmpty(@Nullable String string) {
     if (ExoPlayerLibraryInfo.ASSERTIONS_ENABLED && TextUtils.isEmpty(string)) {
       throw new IllegalArgumentException();
     }
@@ -149,7 +154,8 @@ public final class Assertions {
    * @return The non-null, non-empty string that was validated.
    * @throws IllegalArgumentException If {@code string} is null or 0-length.
    */
-  public static String checkNotEmpty(String string, Object errorMessage) {
+  @EnsuresNonNull({"#1"})
+  public static String checkNotEmpty(@Nullable String string, Object errorMessage) {
     if (ExoPlayerLibraryInfo.ASSERTIONS_ENABLED && TextUtils.isEmpty(string)) {
       throw new IllegalArgumentException(String.valueOf(errorMessage));
     }

library/core/src/main/java/com/google/android/exoplayer2/util/MimeTypes.java

@@ -134,14 +134,13 @@ public final class MimeTypes {
     return BASE_TYPE_APPLICATION.equals(getTopLevelType(mimeType));
   }
 
-
   /**
    * Derives a video sample mimeType from a codecs attribute.
    *
    * @param codecs The codecs attribute.
    * @return The derived video mimeType, or null if it could not be derived.
    */
-  public static String getVideoMediaMimeType(String codecs) {
+  public static @Nullable String getVideoMediaMimeType(@Nullable String codecs) {
     if (codecs == null) {
       return null;
     }
@@ -161,7 +160,7 @@ public final class MimeTypes {
    * @param codecs The codecs attribute.
    * @return The derived audio mimeType, or null if it could not be derived.
    */
-  public static String getAudioMediaMimeType(String codecs) {
+  public static @Nullable String getAudioMediaMimeType(@Nullable String codecs) {
     if (codecs == null) {
       return null;
     }
@@ -181,7 +180,7 @@ public final class MimeTypes {
    * @param codec The codec identifier to derive.
    * @return The mimeType, or null if it could not be derived.
    */
-  public static String getMediaMimeType(String codec) {
+  public static @Nullable String getMediaMimeType(@Nullable String codec) {
     if (codec == null) {
       return null;
     }
@@ -345,7 +344,7 @@ public final class MimeTypes {
    * @param mimeType The mimeType whose top-level type is required.
    * @return The top-level type, or null if the mimeType is null.
    */
-  private static String getTopLevelType(String mimeType) {
+  private static @Nullable String getTopLevelType(@Nullable String mimeType) {
     if (mimeType == null) {
       return null;
     }

library/core/src/main/java/com/google/android/exoplayer2/util/Util.java

@@ -29,6 +29,7 @@ import android.net.Uri;
 import android.os.Build;
 import android.os.Parcel;
 import android.support.annotation.NonNull;
+import android.support.annotation.Nullable;
 import android.text.TextUtils;
 import android.util.Log;
 import android.view.Display;
@@ -190,7 +191,7 @@ public final class Util {
    * @param o2 The second object.
    * @return {@code o1 == null ? o2 == null : o1.equals(o2)}.
    */
-  public static boolean areEqual(Object o1, Object o2) {
+  public static boolean areEqual(@Nullable Object o1, @Nullable Object o2) {
     return o1 == null ? o2 == null : o1.equals(o2);
   }
 
@@ -225,6 +226,20 @@ public final class Util {
   }
 
   /**
+   * Copies and optionally truncates an array. Prevents null array elements created by {@link
+   * Arrays#copyOf(Object[], int)} by ensuring the new length does not exceed the current length.
+   *
+   * @param input The input array.
+   * @param length The output array length. Must be less or equal to the length of the input array.
+   * @return The copied array.
+   */
+  @SuppressWarnings("nullness:assignment.type.incompatible")
+  public static <T> T[] nullSafeArrayCopy(T[] input, int length) {
+    Assertions.checkArgument(length <= input.length);
+    return Arrays.copyOf(input, length);
+  }
+
+  /**
    * Instantiates a new single threaded executor whose thread has the specified name.
    *
    * @param threadName The name of the thread.

library/dash/build.gradle

@@ -34,6 +34,8 @@ android {
 
 dependencies {
     implementation project(modulePrefix + 'library-core')
+    implementation 'org.checkerframework:checker-qual:' + checkerframeworkVersion
+    implementation 'org.checkerframework:checker-compat-qual:' + checkerframeworkVersion
     implementation 'com.android.support:support-annotations:' + supportLibraryVersion
     testImplementation project(modulePrefix + 'testutils-robolectric')
 }

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

@@ -16,6 +16,7 @@
 package com.google.android.exoplayer2.source.dash;
 
 import android.net.Uri;
+import android.support.annotation.Nullable;
 import com.google.android.exoplayer2.C;
 import com.google.android.exoplayer2.Format;
 import com.google.android.exoplayer2.drm.DrmInitData;
@@ -65,7 +66,7 @@ public final class DashUtil {
    * @throws IOException Thrown when there is an error while loading.
    * @throws InterruptedException Thrown if the thread was interrupted.
    */
-  public static DrmInitData loadDrmInitData(DataSource dataSource, Period period)
+  public static @Nullable DrmInitData loadDrmInitData(DataSource dataSource, Period period)
       throws IOException, InterruptedException {
     int primaryTrackType = C.TRACK_TYPE_VIDEO;
     Representation representation = getFirstRepresentation(period, primaryTrackType);
@@ -87,15 +88,16 @@ public final class DashUtil {
    * Loads initialization data for the {@code representation} and returns the sample {@link Format}.
    *
    * @param dataSource The source from which the data should be loaded.
-   * @param trackType The type of the representation. Typically one of the
-   *     {@link com.google.android.exoplayer2.C} {@code TRACK_TYPE_*} constants.
+   * @param trackType The type of the representation. Typically one of the {@link
+   *     com.google.android.exoplayer2.C} {@code TRACK_TYPE_*} constants.
    * @param representation The representation which initialization chunk belongs to.
    * @return the sample {@link Format} of the given representation.
    * @throws IOException Thrown when there is an error while loading.
    * @throws InterruptedException Thrown if the thread was interrupted.
    */
-  public static Format loadSampleFormat(DataSource dataSource, int trackType,
-      Representation representation) throws IOException, InterruptedException {
+  public static @Nullable Format loadSampleFormat(
+      DataSource dataSource, int trackType, Representation representation)
+      throws IOException, InterruptedException {
     ChunkExtractorWrapper extractorWrapper = loadInitializationData(dataSource, trackType,
         representation, false);
     return extractorWrapper == null ? null : extractorWrapper.getSampleFormats()[0];
@@ -106,28 +108,29 @@ public final class DashUtil {
    * ChunkIndex}.
    *
    * @param dataSource The source from which the data should be loaded.
-   * @param trackType The type of the representation. Typically one of the
-   *     {@link com.google.android.exoplayer2.C} {@code TRACK_TYPE_*} constants.
+   * @param trackType The type of the representation. Typically one of the {@link
+   *     com.google.android.exoplayer2.C} {@code TRACK_TYPE_*} constants.
    * @param representation The representation which initialization chunk belongs to.
    * @return The {@link ChunkIndex} of the given representation, or null if no initialization or
    *     index data exists.
    * @throws IOException Thrown when there is an error while loading.
    * @throws InterruptedException Thrown if the thread was interrupted.
    */
-  public static ChunkIndex loadChunkIndex(DataSource dataSource, int trackType,
-      Representation representation) throws IOException, InterruptedException {
+  public static @Nullable ChunkIndex loadChunkIndex(
+      DataSource dataSource, int trackType, Representation representation)
+      throws IOException, InterruptedException {
     ChunkExtractorWrapper extractorWrapper = loadInitializationData(dataSource, trackType,
         representation, true);
     return extractorWrapper == null ? null : (ChunkIndex) extractorWrapper.getSeekMap();
   }
 
   /**
-   * Loads initialization data for the {@code representation} and optionally index data then
-   * returns a {@link ChunkExtractorWrapper} which contains the output.
+   * Loads initialization data for the {@code representation} and optionally index data then returns
+   * a {@link ChunkExtractorWrapper} which contains the output.
    *
    * @param dataSource The source from which the data should be loaded.
-   * @param trackType The type of the representation. Typically one of the
-   *     {@link com.google.android.exoplayer2.C} {@code TRACK_TYPE_*} constants.
+   * @param trackType The type of the representation. Typically one of the {@link
+   *     com.google.android.exoplayer2.C} {@code TRACK_TYPE_*} constants.
    * @param representation The representation which initialization chunk belongs to.
    * @param loadIndex Whether to load index data too.
    * @return A {@link ChunkExtractorWrapper} for the {@code representation}, or null if no
@@ -135,8 +138,9 @@ public final class DashUtil {
    * @throws IOException Thrown when there is an error while loading.
    * @throws InterruptedException Thrown if the thread was interrupted.
    */
-  private static ChunkExtractorWrapper loadInitializationData(DataSource dataSource, int trackType,
-      Representation representation, boolean loadIndex) throws IOException, InterruptedException {
+  private static @Nullable ChunkExtractorWrapper loadInitializationData(
+      DataSource dataSource, int trackType, Representation representation, boolean loadIndex)
+      throws IOException, InterruptedException {
     RangedUri initializationUri = representation.getInitializationUri();
     if (initializationUri == null) {
       return null;
@@ -181,7 +185,7 @@ public final class DashUtil {
     return new ChunkExtractorWrapper(extractor, trackType, format);
   }
 
-  private static Representation getFirstRepresentation(Period period, int type) {
+  private static @Nullable Representation getFirstRepresentation(Period period, int type) {
     int index = period.getAdaptationSetIndex(type);
     if (index == C.INDEX_UNSET) {
       return null;

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

@@ -45,8 +45,10 @@ import java.io.IOException;
 
   EventSampleStream(EventStream eventStream, Format upstreamFormat, boolean eventStreamUpdatable) {
     this.upstreamFormat = upstreamFormat;
+    this.eventStream = eventStream;
     eventMessageEncoder = new EventMessageEncoder();
     pendingSeekPositionUs = C.TIME_UNSET;
+    eventTimesUs = eventStream.presentationTimesUs;
     updateEventStream(eventStream, eventStreamUpdatable);
   }
 

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

@@ -100,6 +100,7 @@ public final class PlayerEmsgHandler implements Handler.Callback {
    *     messages that generate DASH media source events.
    * @param allocator An {@link Allocator} from which allocations can be obtained.
    */
+  @SuppressWarnings("nullness")
   public PlayerEmsgHandler(
       DashManifest manifest, PlayerEmsgCallback playerEmsgCallback, Allocator allocator) {
     this.manifest = manifest;
@@ -237,11 +238,10 @@ public final class PlayerEmsgHandler implements Handler.Callback {
   // Internal methods.
 
   private void handleManifestExpiredMessage(long eventTimeUs, long manifestPublishTimeMsInEmsg) {
-    if (!manifestPublishTimeToExpiryTimeUs.containsKey(manifestPublishTimeMsInEmsg)) {
+    Long previousExpiryTimeUs = manifestPublishTimeToExpiryTimeUs.get(manifestPublishTimeMsInEmsg);
+    if (previousExpiryTimeUs == null) {
       manifestPublishTimeToExpiryTimeUs.put(manifestPublishTimeMsInEmsg, eventTimeUs);
     } else {
-      long previousExpiryTimeUs =
-          manifestPublishTimeToExpiryTimeUs.get(manifestPublishTimeMsInEmsg);
       if (previousExpiryTimeUs > eventTimeUs) {
         manifestPublishTimeToExpiryTimeUs.put(manifestPublishTimeMsInEmsg, eventTimeUs);
       }
@@ -253,10 +253,7 @@ public final class PlayerEmsgHandler implements Handler.Callback {
     notifySourceMediaPresentationEnded();
   }
 
-  private Map.Entry<Long, Long> ceilingExpiryEntryForPublishTime(long publishTimeMs) {
-    if (manifestPublishTimeToExpiryTimeUs.isEmpty()) {
-      return null;
-    }
+  private @Nullable Map.Entry<Long, Long> ceilingExpiryEntryForPublishTime(long publishTimeMs) {
     return manifestPublishTimeToExpiryTimeUs.ceilingEntry(publishTimeMs);
   }
 

library/dash/src/main/java/com/google/android/exoplayer2/source/dash/manifest/Descriptor.java

@@ -49,7 +49,7 @@ public final class Descriptor {
   }
 
   @Override
-  public boolean equals(Object obj) {
+  public boolean equals(@Nullable Object obj) {
     if (this == obj) {
       return true;
     }

library/dash/src/main/java/com/google/android/exoplayer2/source/dash/manifest/RangedUri.java

@@ -16,6 +16,7 @@
 package com.google.android.exoplayer2.source.dash.manifest;
 
 import android.net.Uri;
+import android.support.annotation.Nullable;
 import com.google.android.exoplayer2.C;
 import com.google.android.exoplayer2.util.UriUtil;
 
@@ -46,7 +47,7 @@ public final class RangedUri {
    * @param length The length of the range, or {@link C#LENGTH_UNSET} to indicate that the range is
    *     unbounded.
    */
-  public RangedUri(String referenceUri, long start, long length) {
+  public RangedUri(@Nullable String referenceUri, long start, long length) {
     this.referenceUri = referenceUri == null ? "" : referenceUri;
     this.start = start;
     this.length = length;
@@ -74,18 +75,18 @@ public final class RangedUri {
 
   /**
    * Attempts to merge this {@link RangedUri} with another and an optional common base uri.
-   * <p>
-   * A merge is successful if both instances define the same {@link Uri} after resolution with the
-   * base uri, and if one starts the byte after the other ends, forming a contiguous region with
+   *
+   * <p>A merge is successful if both instances define the same {@link Uri} after resolution with
+   * the base uri, and if one starts the byte after the other ends, forming a contiguous region with
    * no overlap.
-   * <p>
-   * If {@code other} is null then the merge is considered unsuccessful, and null is returned.
+   *
+   * <p>If {@code other} is null then the merge is considered unsuccessful, and null is returned.
    *
    * @param other The {@link RangedUri} to merge.
    * @param baseUri The optional base Uri.
    * @return The merged {@link RangedUri} if the merge was successful. Null otherwise.
    */
-  public RangedUri attemptMerge(RangedUri other, String baseUri) {
+  public @Nullable RangedUri attemptMerge(@Nullable RangedUri other, String baseUri) {
     final String resolvedUri = resolveUriString(baseUri);
     if (other == null || !resolvedUri.equals(other.resolveUriString(baseUri))) {
       return null;
@@ -113,7 +114,7 @@ public final class RangedUri {
   }
 
   @Override
-  public boolean equals(Object obj) {
+  public boolean equals(@Nullable Object obj) {
     if (this == obj) {
       return true;
     }

library/dash/src/main/java/com/google/android/exoplayer2/source/dash/manifest/RepresentationKey.java

@@ -18,6 +18,7 @@ package com.google.android.exoplayer2.source.dash.manifest;
 import android.os.Parcel;
 import android.os.Parcelable;
 import android.support.annotation.NonNull;
+import android.support.annotation.Nullable;
 
 /**
  * Uniquely identifies a {@link Representation} in a {@link DashManifest}.
@@ -81,7 +82,7 @@ public final class RepresentationKey implements Parcelable, Comparable<Represent
   }
 
   @Override
-  public boolean equals(Object o) {
+  public boolean equals(@Nullable Object o) {
     if (this == o) {
       return true;
     }

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

@@ -151,7 +151,7 @@ public final class DashDownloader extends SegmentDownloader<DashManifest, Repres
     out.add(new Segment(startTimeUs, dataSpec));
   }
 
-  private static DashSegmentIndex getSegmentIndex(
+  private static @Nullable DashSegmentIndex getSegmentIndex(
       DataSource dataSource, int trackType, Representation representation)
       throws IOException, InterruptedException {
     DashSegmentIndex index = representation.getIndex();