Fix track selection nullability issues.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=199266768

library/core/build.gradle

@@ -54,6 +54,7 @@ android {
 dependencies {
     implementation 'com.android.support:support-annotations:' + supportLibraryVersion
     compileOnly 'org.checkerframework:checker-qual:' + checkerframeworkVersion
+    compileOnly 'org.checkerframework:checker-compat-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/trackselection/AdaptiveTrackSelection.java

@@ -15,6 +15,7 @@
  */
 package com.google.android.exoplayer2.trackselection;
 
+import android.support.annotation.Nullable;
 import com.google.android.exoplayer2.C;
 import com.google.android.exoplayer2.Format;
 import com.google.android.exoplayer2.source.TrackGroup;
@@ -242,9 +243,11 @@ public class AdaptiveTrackSelection extends BaseTrackSelection {
     this.minTimeBetweenBufferReevaluationMs = minTimeBetweenBufferReevaluationMs;
     this.clock = clock;
     playbackSpeed = 1f;
-    selectedIndex = determineIdealSelectedIndex(Long.MIN_VALUE);
     reason = C.SELECTION_REASON_INITIAL;
     lastBufferEvaluationMs = C.TIME_UNSET;
+    @SuppressWarnings("nullness:method.invocation.invalid")
+    int selectedIndex = determineIdealSelectedIndex(Long.MIN_VALUE);
+    this.selectedIndex = selectedIndex;
   }
 
   @Override
@@ -301,7 +304,7 @@ public class AdaptiveTrackSelection extends BaseTrackSelection {
   }
 
   @Override
-  public Object getSelectionData() {
+  public @Nullable Object getSelectionData() {
     return null;
   }
 

library/core/src/main/java/com/google/android/exoplayer2/trackselection/DefaultTrackSelector.java

@@ -19,7 +19,6 @@ import android.content.Context;
 import android.graphics.Point;
 import android.os.Parcel;
 import android.os.Parcelable;
-import android.support.annotation.NonNull;
 import android.support.annotation.Nullable;
 import android.text.TextUtils;
 import android.util.Pair;
@@ -44,6 +43,7 @@ import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
 import java.util.concurrent.atomic.AtomicReference;
+import org.checkerframework.checker.nullness.compatqual.NullableType;
 
 /**
  * A default {@link TrackSelector} suitable for most use cases. Track selections are made according
@@ -161,8 +161,8 @@ public class DefaultTrackSelector extends MappingTrackSelector {
     private final SparseArray<Map<TrackGroupArray, SelectionOverride>> selectionOverrides;
     private final SparseBooleanArray rendererDisabledFlags;
 
-    private String preferredAudioLanguage;
+    private @Nullable String preferredAudioLanguage;
-    private String preferredTextLanguage;
+    private @Nullable String preferredTextLanguage;
     private boolean selectUndeterminedTextLanguage;
     private int disabledTextTrackSelectionFlags;
     private boolean forceLowestBitrate;
@@ -572,14 +572,14 @@ public class DefaultTrackSelector extends MappingTrackSelector {
      * The preferred language for audio, as well as for forced text tracks, as an ISO 639-2/T tag.
      * {@code null} selects the default track, or the first track if there's no default.
      */
-    public final String preferredAudioLanguage;
+    public final @Nullable String preferredAudioLanguage;
 
     // Text
     /**
      * The preferred language for text tracks as an ISO 639-2/T tag. {@code null} selects the
      * default track if there is one, or no track otherwise.
      */
-    public final String preferredTextLanguage;
+    public final @Nullable String preferredTextLanguage;
     /**
      * Whether a text track with undetermined language should be selected if no track with
      * {@link #preferredTextLanguage} is available, or if {@link #preferredTextLanguage} is unset.
@@ -673,8 +673,8 @@ public class DefaultTrackSelector extends MappingTrackSelector {
     /* package */ Parameters(
         SparseArray<Map<TrackGroupArray, SelectionOverride>> selectionOverrides,
         SparseBooleanArray rendererDisabledFlags,
-        String preferredAudioLanguage,
+        @Nullable String preferredAudioLanguage,
-        String preferredTextLanguage,
+        @Nullable String preferredTextLanguage,
         boolean selectUndeterminedTextLanguage,
         int disabledTextTrackSelectionFlags,
         boolean forceLowestBitrate,
@@ -759,7 +759,8 @@ public class DefaultTrackSelector extends MappingTrackSelector {
      * @param groups The {@link TrackGroupArray}.
      * @return The override, or null if no override exists.
      */
-    public final SelectionOverride getSelectionOverride(int rendererIndex, TrackGroupArray groups) {
+    public final @Nullable SelectionOverride getSelectionOverride(
+        int rendererIndex, TrackGroupArray groups) {
       Map<TrackGroupArray, SelectionOverride> overrides = selectionOverrides.get(rendererIndex);
       return overrides != null ? overrides.get(groups) : null;
     }
@@ -816,8 +817,9 @@ public class DefaultTrackSelector extends MappingTrackSelector {
       result = 31 * result + viewportHeight;
       result = 31 * result + maxVideoBitrate;
       result = 31 * result + tunnelingAudioSessionId;
-      result = 31 * result + preferredAudioLanguage.hashCode();
+      result =
-      result = 31 * result + preferredTextLanguage.hashCode();
+          31 * result + (preferredAudioLanguage == null ? 0 : preferredAudioLanguage.hashCode());
+      result = 31 * result + (preferredTextLanguage == null ? 0 : preferredTextLanguage.hashCode());
       return result;
     }
 
@@ -1042,7 +1044,7 @@ public class DefaultTrackSelector extends MappingTrackSelector {
   private static final int[] NO_TRACKS = new int[0];
   private static final int WITHIN_RENDERER_CAPABILITIES_BONUS = 1000;
 
-  private final TrackSelection.Factory adaptiveTrackSelectionFactory;
+  private final @Nullable TrackSelection.Factory adaptiveTrackSelectionFactory;
   private final AtomicReference<Parameters> parametersReference;
 
   /**
@@ -1069,7 +1071,7 @@ public class DefaultTrackSelector extends MappingTrackSelector {
    * @param adaptiveTrackSelectionFactory A factory for adaptive {@link TrackSelection}s, or null if
    *     the selector should not support adaptive tracks.
    */
-  public DefaultTrackSelector(TrackSelection.Factory adaptiveTrackSelectionFactory) {
+  public DefaultTrackSelector(@Nullable TrackSelection.Factory adaptiveTrackSelectionFactory) {
     this.adaptiveTrackSelectionFactory = adaptiveTrackSelectionFactory;
     parametersReference = new AtomicReference<>(Parameters.DEFAULT);
   }
@@ -1139,7 +1141,8 @@ public class DefaultTrackSelector extends MappingTrackSelector {
 
   /** @deprecated Use {@link Parameters#getSelectionOverride(int, TrackGroupArray)}. */
   @Deprecated
-  public final SelectionOverride getSelectionOverride(int rendererIndex, TrackGroupArray groups) {
+  public final @Nullable SelectionOverride getSelectionOverride(
+      int rendererIndex, TrackGroupArray groups) {
     return getParameters().getSelectionOverride(rendererIndex, groups);
   }
 
@@ -1170,14 +1173,15 @@ public class DefaultTrackSelector extends MappingTrackSelector {
   // MappingTrackSelector implementation.
 
   @Override
-  protected final Pair<RendererConfiguration[], TrackSelection[]> selectTracks(
+  protected final Pair<@NullableType RendererConfiguration[], @NullableType TrackSelection[]>
+      selectTracks(
           MappedTrackInfo mappedTrackInfo,
           int[][][] rendererFormatSupports,
           int[] rendererMixedMimeTypeAdaptationSupports)
           throws ExoPlaybackException {
     Parameters params = parametersReference.get();
     int rendererCount = mappedTrackInfo.getRendererCount();
-    TrackSelection[] rendererTrackSelections =
+    @NullableType TrackSelection[] rendererTrackSelections =
         selectAllTracks(
             mappedTrackInfo,
             rendererFormatSupports,
@@ -1200,7 +1204,8 @@ public class DefaultTrackSelector extends MappingTrackSelector {
                     rendererTrackGroups.get(override.groupIndex), override.tracks[0]);
           } else {
             rendererTrackSelections[i] =
-                adaptiveTrackSelectionFactory.createTrackSelection(
+                Assertions.checkNotNull(adaptiveTrackSelectionFactory)
+                    .createTrackSelection(
                         rendererTrackGroups.get(override.groupIndex), override.tracks);
           }
         }
@@ -1209,7 +1214,8 @@ public class DefaultTrackSelector extends MappingTrackSelector {
 
     // Initialize the renderer configurations to the default configuration for all renderers with
     // selections, and null otherwise.
-    RendererConfiguration[] rendererConfigurations = new RendererConfiguration[rendererCount];
+    @NullableType RendererConfiguration[] rendererConfigurations =
+        new RendererConfiguration[rendererCount];
     for (int i = 0; i < rendererCount; i++) {
       boolean forceRendererDisabled = params.getRendererDisabled(i);
       boolean rendererEnabled =
@@ -1248,14 +1254,14 @@ public class DefaultTrackSelector extends MappingTrackSelector {
    *     disabled, unless RendererCapabilities#getTrackType()} is {@link C#TRACK_TYPE_NONE}.
    * @throws ExoPlaybackException If an error occurs while selecting the tracks.
    */
-  protected TrackSelection[] selectAllTracks(
+  protected @NullableType TrackSelection[] selectAllTracks(
       MappedTrackInfo mappedTrackInfo,
       int[][][] rendererFormatSupports,
       int[] rendererMixedMimeTypeAdaptationSupports,
       Parameters params)
       throws ExoPlaybackException {
     int rendererCount = mappedTrackInfo.getRendererCount();
-    TrackSelection[] rendererTrackSelections = new TrackSelection[rendererCount];
+    @NullableType TrackSelection[] rendererTrackSelections = new TrackSelection[rendererCount];
 
     boolean seenVideoRendererWithMappedTracks = false;
     boolean selectedVideoTracks = false;
@@ -1331,12 +1337,12 @@ public class DefaultTrackSelector extends MappingTrackSelector {
    * @return The {@link TrackSelection} for the renderer, or null if no selection was made.
    * @throws ExoPlaybackException If an error occurs while selecting the tracks.
    */
-  protected TrackSelection selectVideoTrack(
+  protected @Nullable TrackSelection selectVideoTrack(
       TrackGroupArray groups,
       int[][] formatSupports,
       int mixedMimeTypeAdaptationSupports,
       Parameters params,
-      TrackSelection.Factory adaptiveTrackSelectionFactory)
+      @Nullable TrackSelection.Factory adaptiveTrackSelectionFactory)
       throws ExoPlaybackException {
     TrackSelection selection = null;
     if (!params.forceLowestBitrate && adaptiveTrackSelectionFactory != null) {
@@ -1354,7 +1360,7 @@ public class DefaultTrackSelector extends MappingTrackSelector {
     return selection;
   }
 
-  private static TrackSelection selectAdaptiveVideoTrack(
+  private static @Nullable TrackSelection selectAdaptiveVideoTrack(
       TrackGroupArray groups,
       int[][] formatSupport,
       int mixedMimeTypeAdaptationSupports,
@@ -1374,7 +1380,8 @@ public class DefaultTrackSelector extends MappingTrackSelector {
           params.maxVideoBitrate, params.viewportWidth, params.viewportHeight,
           params.viewportOrientationMayChange);
       if (adaptiveTracks.length > 0) {
-        return adaptiveTrackSelectionFactory.createTrackSelection(group, adaptiveTracks);
+        return Assertions.checkNotNull(adaptiveTrackSelectionFactory)
+            .createTrackSelection(group, adaptiveTracks);
       }
     }
     return null;
@@ -1397,7 +1404,7 @@ public class DefaultTrackSelector extends MappingTrackSelector {
     String selectedMimeType = null;
     if (!allowMixedMimeTypes) {
       // Select the mime type for which we have the most adaptive tracks.
-      HashSet<String> seenMimeTypes = new HashSet<>();
+      HashSet<@NullableType String> seenMimeTypes = new HashSet<>();
       int selectedMimeTypeTrackCount = 0;
       for (int i = 0; i < selectedTrackIndices.size(); i++) {
         int trackIndex = selectedTrackIndices.get(i);
@@ -1421,9 +1428,15 @@ public class DefaultTrackSelector extends MappingTrackSelector {
     return selectedTrackIndices.size() < 2 ? NO_TRACKS : Util.toArray(selectedTrackIndices);
   }
 
-  private static int getAdaptiveVideoTrackCountForMimeType(TrackGroup group, int[] formatSupport,
+  private static int getAdaptiveVideoTrackCountForMimeType(
-      int requiredAdaptiveSupport, String mimeType, int maxVideoWidth, int maxVideoHeight,
+      TrackGroup group,
-      int maxVideoBitrate, List<Integer> selectedTrackIndices) {
+      int[] formatSupport,
+      int requiredAdaptiveSupport,
+      @Nullable String mimeType,
+      int maxVideoWidth,
+      int maxVideoHeight,
+      int maxVideoBitrate,
+      List<Integer> selectedTrackIndices) {
     int adaptiveTrackCount = 0;
     for (int i = 0; i < selectedTrackIndices.size(); i++) {
       int trackIndex = selectedTrackIndices.get(i);
@@ -1436,9 +1449,15 @@ public class DefaultTrackSelector extends MappingTrackSelector {
     return adaptiveTrackCount;
   }
 
-  private static void filterAdaptiveVideoTrackCountForMimeType(TrackGroup group,
+  private static void filterAdaptiveVideoTrackCountForMimeType(
-      int[] formatSupport, int requiredAdaptiveSupport, String mimeType, int maxVideoWidth,
+      TrackGroup group,
-      int maxVideoHeight, int maxVideoBitrate, List<Integer> selectedTrackIndices) {
+      int[] formatSupport,
+      int requiredAdaptiveSupport,
+      @Nullable String mimeType,
+      int maxVideoWidth,
+      int maxVideoHeight,
+      int maxVideoBitrate,
+      List<Integer> selectedTrackIndices) {
     for (int i = selectedTrackIndices.size() - 1; i >= 0; i--) {
       int trackIndex = selectedTrackIndices.get(i);
       if (!isSupportedAdaptiveVideoTrack(group.getFormat(trackIndex), mimeType,
@@ -1449,8 +1468,13 @@ public class DefaultTrackSelector extends MappingTrackSelector {
     }
   }
 
-  private static boolean isSupportedAdaptiveVideoTrack(Format format, String mimeType,
+  private static boolean isSupportedAdaptiveVideoTrack(
-      int formatSupport, int requiredAdaptiveSupport, int maxVideoWidth, int maxVideoHeight,
+      Format format,
+      @Nullable String mimeType,
+      int formatSupport,
+      int requiredAdaptiveSupport,
+      int maxVideoWidth,
+      int maxVideoHeight,
       int maxVideoBitrate) {
     return isSupported(formatSupport, false) && ((formatSupport & requiredAdaptiveSupport) != 0)
         && (mimeType == null || Util.areEqual(format.sampleMimeType, mimeType))
@@ -1459,7 +1483,7 @@ public class DefaultTrackSelector extends MappingTrackSelector {
         && (format.bitrate == Format.NO_VALUE || format.bitrate <= maxVideoBitrate);
   }
 
-  private static TrackSelection selectFixedVideoTrack(
+  private static @Nullable TrackSelection selectFixedVideoTrack(
       TrackGroupArray groups, int[][] formatSupports, Parameters params) {
     TrackGroup selectedGroup = null;
     int selectedTrackIndex = 0;
@@ -1537,12 +1561,12 @@ public class DefaultTrackSelector extends MappingTrackSelector {
    * @return The {@link TrackSelection} for the renderer, or null if no selection was made.
    * @throws ExoPlaybackException If an error occurs while selecting the tracks.
    */
-  protected TrackSelection selectAudioTrack(
+  protected @Nullable TrackSelection selectAudioTrack(
       TrackGroupArray groups,
       int[][] formatSupports,
       int mixedMimeTypeAdaptationSupports,
       Parameters params,
-      TrackSelection.Factory adaptiveTrackSelectionFactory)
+      @Nullable TrackSelection.Factory adaptiveTrackSelectionFactory)
       throws ExoPlaybackException {
     int selectedTrackIndex = C.INDEX_UNSET;
     int selectedGroupIndex = C.INDEX_UNSET;
@@ -1606,8 +1630,8 @@ public class DefaultTrackSelector extends MappingTrackSelector {
       int[] adaptiveIndices = new int[selectedConfigurationTrackCount];
       int index = 0;
       for (int i = 0; i < group.length; i++) {
-        if (isSupportedAdaptiveAudioTrack(group.getFormat(i), formatSupport[i],
+        if (isSupportedAdaptiveAudioTrack(
-            selectedConfiguration)) {
+            group.getFormat(i), formatSupport[i], Assertions.checkNotNull(selectedConfiguration))) {
           adaptiveIndices[index++] = i;
         }
       }
@@ -1648,7 +1672,7 @@ public class DefaultTrackSelector extends MappingTrackSelector {
    * @return The {@link TrackSelection} for the renderer, or null if no selection was made.
    * @throws ExoPlaybackException If an error occurs while selecting the tracks.
    */
-  protected TrackSelection selectTextTrack(
+  protected @Nullable TrackSelection selectTextTrack(
       TrackGroupArray groups, int[][] formatSupport, Parameters params)
       throws ExoPlaybackException {
     TrackGroup selectedGroup = null;
@@ -1721,7 +1745,7 @@ public class DefaultTrackSelector extends MappingTrackSelector {
    * @return The {@link TrackSelection} for the renderer, or null if no selection was made.
    * @throws ExoPlaybackException If an error occurs while selecting the tracks.
    */
-  protected TrackSelection selectOtherTrack(
+  protected @Nullable TrackSelection selectOtherTrack(
       int trackType, TrackGroupArray groups, int[][] formatSupport, Parameters params)
       throws ExoPlaybackException {
     TrackGroup selectedGroup = null;
@@ -1768,8 +1792,8 @@ public class DefaultTrackSelector extends MappingTrackSelector {
   private static void maybeConfigureRenderersForTunneling(
       MappedTrackInfo mappedTrackInfo,
       int[][][] renderererFormatSupports,
-      RendererConfiguration[] rendererConfigurations,
+      @NullableType RendererConfiguration[] rendererConfigurations,
-      TrackSelection[] trackSelections,
+      @NullableType TrackSelection[] trackSelections,
       int tunnelingAudioSessionId) {
     if (tunnelingAudioSessionId == C.AUDIO_SESSION_ID_UNSET) {
       return;
@@ -1883,15 +1907,15 @@ public class DefaultTrackSelector extends MappingTrackSelector {
   }
 
   /**
-   * Returns whether a {@link Format} specifies a particular language, or {@code false} if
+   * Returns whether a {@link Format} specifies a particular language, or {@code false} if {@code
-   * {@code language} is null.
+   * language} is null.
    *
    * @param format The {@link Format}.
    * @param language The language.
    * @return Whether the format specifies the language, or {@code false} if {@code language} is
    *     null.
    */
-  protected static boolean formatHasLanguage(Format format, String language) {
+  protected static boolean formatHasLanguage(Format format, @Nullable String language) {
     return language != null
         && TextUtils.equals(language, Util.normalizeLanguageCode(format.language));
   }
@@ -1997,7 +2021,7 @@ public class DefaultTrackSelector extends MappingTrackSelector {
      *     negative integer if this score is worse than the other.
      */
     @Override
-    public int compareTo(@NonNull AudioTrackScore other) {
+    public int compareTo(AudioTrackScore other) {
       if (this.withinRendererCapabilitiesScore != other.withinRendererCapabilitiesScore) {
         return compareInts(this.withinRendererCapabilitiesScore,
             other.withinRendererCapabilitiesScore);
@@ -2066,9 +2090,9 @@ public class DefaultTrackSelector extends MappingTrackSelector {
 
     public final int channelCount;
     public final int sampleRate;
-    public final String mimeType;
+    public final @Nullable String mimeType;
 
-    public AudioConfigurationTuple(int channelCount, int sampleRate, String mimeType) {
+    public AudioConfigurationTuple(int channelCount, int sampleRate, @Nullable String mimeType) {
       this.channelCount = channelCount;
       this.sampleRate = sampleRate;
       this.mimeType = mimeType;

library/core/src/main/java/com/google/android/exoplayer2/trackselection/FixedTrackSelection.java

@@ -15,6 +15,7 @@
  */
 package com.google.android.exoplayer2.trackselection;
 
+import android.support.annotation.Nullable;
 import com.google.android.exoplayer2.C;
 import com.google.android.exoplayer2.source.TrackGroup;
 import com.google.android.exoplayer2.util.Assertions;
@@ -30,7 +31,7 @@ public final class FixedTrackSelection extends BaseTrackSelection {
   public static final class Factory implements TrackSelection.Factory {
 
     private final int reason;
-    private final Object data;
+    private final @Nullable Object data;
 
     public Factory() {
       this.reason = C.SELECTION_REASON_UNKNOWN;
@@ -41,7 +42,7 @@ public final class FixedTrackSelection extends BaseTrackSelection {
      * @param reason A reason for the track selection.
      * @param data Optional data associated with the track selection.
      */
-    public Factory(int reason, Object data) {
+    public Factory(int reason, @Nullable Object data) {
       this.reason = reason;
       this.data = data;
     }
@@ -51,11 +52,10 @@ public final class FixedTrackSelection extends BaseTrackSelection {
       Assertions.checkArgument(tracks.length == 1);
       return new FixedTrackSelection(group, tracks[0], reason, data);
     }
-
   }
 
   private final int reason;
-  private final Object data;
+  private final @Nullable Object data;
 
   /**
    * @param group The {@link TrackGroup}. Must not be null.
@@ -71,7 +71,7 @@ public final class FixedTrackSelection extends BaseTrackSelection {
    * @param reason A reason for the track selection.
    * @param data Optional data associated with the track selection.
    */
-  public FixedTrackSelection(TrackGroup group, int track, int reason, Object data) {
+  public FixedTrackSelection(TrackGroup group, int track, int reason, @Nullable Object data) {
     super(group, track);
     this.reason = reason;
     this.data = data;
@@ -94,7 +94,7 @@ public final class FixedTrackSelection extends BaseTrackSelection {
   }
 
   @Override
-  public Object getSelectionData() {
+  public @Nullable Object getSelectionData() {
     return data;
   }
 

library/core/src/main/java/com/google/android/exoplayer2/trackselection/MappingTrackSelector.java

@@ -16,6 +16,7 @@
 package com.google.android.exoplayer2.trackselection;
 
 import android.support.annotation.IntDef;
+import android.support.annotation.Nullable;
 import android.util.Pair;
 import com.google.android.exoplayer2.C;
 import com.google.android.exoplayer2.ExoPlaybackException;
@@ -28,6 +29,7 @@ import com.google.android.exoplayer2.util.Util;
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
 import java.util.Arrays;
+import org.checkerframework.checker.nullness.compatqual.NullableType;
 
 /**
  * Base class for {@link TrackSelector}s that first establish a mapping between {@link TrackGroup}s
@@ -301,13 +303,13 @@ public abstract class MappingTrackSelector extends TrackSelector {
 
   }
 
-  private MappedTrackInfo currentMappedTrackInfo;
+  private @Nullable MappedTrackInfo currentMappedTrackInfo;
 
   /**
    * Returns the mapping information for the currently active track selection, or null if no
    * selection is currently active.
    */
-  public final MappedTrackInfo getCurrentMappedTrackInfo() {
+  public final @Nullable MappedTrackInfo getCurrentMappedTrackInfo() {
     return currentMappedTrackInfo;
   }
 
@@ -357,9 +359,11 @@ public abstract class MappingTrackSelector extends TrackSelector {
     int[] rendererTrackTypes = new int[rendererCapabilities.length];
     for (int i = 0; i < rendererCapabilities.length; i++) {
       int rendererTrackGroupCount = rendererTrackGroupCounts[i];
-      rendererTrackGroupArrays[i] = new TrackGroupArray(
+      rendererTrackGroupArrays[i] =
-          Arrays.copyOf(rendererTrackGroups[i], rendererTrackGroupCount));
+          new TrackGroupArray(
-      rendererFormatSupports[i] = Arrays.copyOf(rendererFormatSupports[i], rendererTrackGroupCount);
+              Util.nullSafeArrayCopy(rendererTrackGroups[i], rendererTrackGroupCount));
+      rendererFormatSupports[i] =
+          Util.nullSafeArrayCopy(rendererFormatSupports[i], rendererTrackGroupCount);
       rendererTrackTypes[i] = rendererCapabilities[i].getTrackType();
     }
 
@@ -367,7 +371,7 @@ public abstract class MappingTrackSelector extends TrackSelector {
     int unmappedTrackGroupCount = rendererTrackGroupCounts[rendererCapabilities.length];
     TrackGroupArray unmappedTrackGroupArray =
         new TrackGroupArray(
-            Arrays.copyOf(
+            Util.nullSafeArrayCopy(
                 rendererTrackGroups[rendererCapabilities.length], unmappedTrackGroupCount));
 
     // Package up the track information and selections.
@@ -379,7 +383,7 @@ public abstract class MappingTrackSelector extends TrackSelector {
             rendererFormatSupports,
             unmappedTrackGroupArray);
 
-    Pair<RendererConfiguration[], TrackSelection[]> result =
+    Pair<@NullableType RendererConfiguration[], @NullableType TrackSelection[]> result =
         selectTracks(
             mappedTrackInfo, rendererFormatSupports, rendererMixedMimeTypeAdaptationSupports);
     return new TrackSelectorResult(result.first, result.second, mappedTrackInfo);
@@ -399,7 +403,8 @@ public abstract class MappingTrackSelector extends TrackSelector {
    *     RendererCapabilities#getTrackType()} is {@link C#TRACK_TYPE_NONE}.
    * @throws ExoPlaybackException If an error occurs while selecting the tracks.
    */
-  protected abstract Pair<RendererConfiguration[], TrackSelection[]> selectTracks(
+  protected abstract Pair<@NullableType RendererConfiguration[], @NullableType TrackSelection[]>
+      selectTracks(
           MappedTrackInfo mappedTrackInfo,
           int[][][] rendererFormatSupports,
           int[] rendererMixedMimeTypeAdaptationSupport)

library/core/src/main/java/com/google/android/exoplayer2/trackselection/RandomTrackSelection.java

@@ -16,6 +16,7 @@
 package com.google.android.exoplayer2.trackselection;
 
 import android.os.SystemClock;
+import android.support.annotation.Nullable;
 import com.google.android.exoplayer2.C;
 import com.google.android.exoplayer2.source.TrackGroup;
 import java.util.Random;
@@ -47,7 +48,6 @@ public final class RandomTrackSelection extends BaseTrackSelection {
     public RandomTrackSelection createTrackSelection(TrackGroup group, int... tracks) {
       return new RandomTrackSelection(group, tracks, random);
     }
-
   }
 
   private final Random random;
@@ -123,7 +123,7 @@ public final class RandomTrackSelection extends BaseTrackSelection {
   }
 
   @Override
-  public Object getSelectionData() {
+  public @Nullable Object getSelectionData() {
     return null;
   }
 

library/core/src/main/java/com/google/android/exoplayer2/trackselection/TrackSelection.java

@@ -15,6 +15,7 @@
  */
 package com.google.android.exoplayer2.trackselection;
 
+import android.support.annotation.Nullable;
 import com.google.android.exoplayer2.C;
 import com.google.android.exoplayer2.Format;
 import com.google.android.exoplayer2.source.TrackGroup;
@@ -129,10 +130,8 @@ public interface TrackSelection {
    */
   int getSelectionReason();
 
-  /**
+  /** Returns optional data associated with the current track selection. */
-   * Returns optional data associated with the current track selection.
+  @Nullable Object getSelectionData();
-   */
-  Object getSelectionData();
 
   // Adaptation.
 

library/core/src/main/java/com/google/android/exoplayer2/trackselection/TrackSelectionArray.java

@@ -17,6 +17,7 @@ package com.google.android.exoplayer2.trackselection;
 
 import android.support.annotation.Nullable;
 import java.util.Arrays;
+import org.checkerframework.checker.nullness.compatqual.NullableType;
 
 /** An array of {@link TrackSelection}s. */
 public final class TrackSelectionArray {
@@ -24,15 +25,13 @@ public final class TrackSelectionArray {
   /** The length of this array. */
   public final int length;
 
-  private final TrackSelection[] trackSelections;
+  private final @NullableType TrackSelection[] trackSelections;
 
   // Lazily initialized hashcode.
   private int hashCode;
 
-  /**
+  /** @param trackSelections The selections. Must not be null, but may contain null elements. */
-   * @param trackSelections The selections. Must not be null, but may contain null elements.
+  public TrackSelectionArray(@NullableType TrackSelection... trackSelections) {
-   */
-  public TrackSelectionArray(TrackSelection... trackSelections) {
     this.trackSelections = trackSelections;
     this.length = trackSelections.length;
   }
@@ -43,14 +42,12 @@ public final class TrackSelectionArray {
    * @param index The index of the selection.
    * @return The selection.
    */
-  public TrackSelection get(int index) {
+  public @Nullable TrackSelection get(int index) {
     return trackSelections[index];
   }
 
-  /**
+  /** Returns the selections in a newly allocated array. */
-   * Returns the selections in a newly allocated array.
+  public @NullableType TrackSelection[] getAll() {
-   */
-  public TrackSelection[] getAll() {
     return trackSelections.clone();
   }
 

library/core/src/main/java/com/google/android/exoplayer2/trackselection/TrackSelector.java

@@ -15,6 +15,7 @@
  */
 package com.google.android.exoplayer2.trackselection;
 
+import android.support.annotation.Nullable;
 import com.google.android.exoplayer2.ExoPlaybackException;
 import com.google.android.exoplayer2.ExoPlayer;
 import com.google.android.exoplayer2.Renderer;
@@ -89,7 +90,7 @@ public abstract class TrackSelector {
 
   }
 
-  private InvalidationListener listener;
+  private @Nullable InvalidationListener listener;
 
   /**
    * Called by the player to initialize the selector.

library/core/src/main/java/com/google/android/exoplayer2/trackselection/TrackSelectorResult.java

@@ -17,6 +17,7 @@ package com.google.android.exoplayer2.trackselection;
 
 import com.google.android.exoplayer2.RendererConfiguration;
 import com.google.android.exoplayer2.util.Util;
+import org.checkerframework.checker.nullness.compatqual.NullableType;
 
 /**
  * The result of a {@link TrackSelector} operation.
@@ -29,7 +30,7 @@ public final class TrackSelectorResult {
    * A {@link RendererConfiguration} for each renderer. A null entry indicates the corresponding
    * renderer should be disabled.
    */
-  public final RendererConfiguration[] rendererConfigurations;
+  public final @NullableType RendererConfiguration[] rendererConfigurations;
   /**
    * A {@link TrackSelectionArray} containing the track selection for each renderer.
    */
@@ -48,7 +49,9 @@ public final class TrackSelectorResult {
    *     TrackSelector#onSelectionActivated(Object)} should the selection be activated.
    */
   public TrackSelectorResult(
-      RendererConfiguration[] rendererConfigurations, TrackSelection[] selections, Object info) {
+      @NullableType RendererConfiguration[] rendererConfigurations,
+      @NullableType TrackSelection[] selections,
+      Object info) {
     this.rendererConfigurations = rendererConfigurations;
     this.selections = new TrackSelectionArray(selections);
     this.info = info;

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

@@ -311,10 +311,10 @@ public final class Util {
    * Returns a normalized RFC 639-2/T code for {@code language}.
    *
    * @param language A case-insensitive ISO 639 alpha-2 or alpha-3 language code.
-   * @return The all-lowercase normalized code, or null if the input was null, or
+   * @return The all-lowercase normalized code, or null if the input was null, or {@code
-   *     {@code language.toLowerCase()} if the language could not be normalized.
+   *     language.toLowerCase()} if the language could not be normalized.
    */
-  public static String normalizeLanguageCode(String language) {
+  public static @Nullable String normalizeLanguageCode(@Nullable String language) {
     try {
       return language == null ? null : new Locale(language).getISO3Language();
     } catch (MissingResourceException e) {

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

@@ -203,7 +203,9 @@ public class TrackSelectionView extends LinearLayout {
       removeViewAt(i);
     }
 
-    if (trackSelector == null) {
+    MappingTrackSelector.MappedTrackInfo trackInfo =
+        trackSelector == null ? null : trackSelector.getCurrentMappedTrackInfo();
+    if (trackSelector == null || trackInfo == null) {
       // The view is not initialized.
       disableView.setEnabled(false);
       defaultView.setEnabled(false);
@@ -212,7 +214,6 @@ public class TrackSelectionView extends LinearLayout {
     disableView.setEnabled(true);
     defaultView.setEnabled(true);
 
-    MappingTrackSelector.MappedTrackInfo trackInfo = trackSelector.getCurrentMappedTrackInfo();
     trackGroups = trackInfo.getTrackGroups(rendererIndex);
 
     DefaultTrackSelector.Parameters parameters = trackSelector.getParameters();