diff --git a/extensions/okhttp/src/main/java/com/google/android/exoplayer2/ext/okhttp/OkHttpDataSource.java b/extensions/okhttp/src/main/java/com/google/android/exoplayer2/ext/okhttp/OkHttpDataSource.java
index fac35bd427..167fc68e86 100644
--- a/extensions/okhttp/src/main/java/com/google/android/exoplayer2/ext/okhttp/OkHttpDataSource.java
+++ b/extensions/okhttp/src/main/java/com/google/android/exoplayer2/ext/okhttp/OkHttpDataSource.java
@@ -16,8 +16,8 @@
 package com.google.android.exoplayer2.ext.okhttp;
 
 import android.net.Uri;
+import android.support.annotation.NonNull;
 import android.support.annotation.Nullable;
-
 import com.google.android.exoplayer2.C;
 import com.google.android.exoplayer2.upstream.DataSourceException;
 import com.google.android.exoplayer2.upstream.DataSpec;
@@ -47,13 +47,14 @@ public class OkHttpDataSource implements HttpDataSource {
 
   private static final AtomicReference<byte[]> skipBufferReference = new AtomicReference<>();
 
-  private final Call.Factory callFactory;
-  private final String userAgent;
-  private final Predicate<String> contentTypePredicate;
-  private final TransferListener<? super OkHttpDataSource> listener;
-  private final CacheControl cacheControl;
-  private final RequestProperties defaultRequestProperties;
-  private final RequestProperties requestProperties;
+  @NonNull private final Call.Factory callFactory;
+  @NonNull private final RequestProperties requestProperties;
+
+  @Nullable private final String userAgent;
+  @Nullable private final Predicate<String> contentTypePredicate;
+  @Nullable private final TransferListener<? super OkHttpDataSource> listener;
+  @Nullable private final CacheControl cacheControl;
+  @Nullable private final RequestProperties defaultRequestProperties;
 
   private DataSpec dataSpec;
   private Response response;
@@ -69,33 +70,34 @@ public class OkHttpDataSource implements HttpDataSource {
   /**
    * @param callFactory A {@link Call.Factory} (typically an {@link okhttp3.OkHttpClient}) for use
    *     by the source.
-   * @param userAgent An optional User-Agent string that should be used.
+   * @param userAgent An optional User-Agent string.
    * @param contentTypePredicate An optional {@link Predicate}. If a content type is rejected by the
    *     predicate then a InvalidContentTypeException} is thrown from {@link #open(DataSpec)}.
    */
-  public OkHttpDataSource(Call.Factory callFactory, @Nullable String userAgent,
-      Predicate<String> contentTypePredicate) {
+  public OkHttpDataSource(@NonNull Call.Factory callFactory, @Nullable String userAgent,
+      @Nullable Predicate<String> contentTypePredicate) {
     this(callFactory, userAgent, contentTypePredicate, null);
   }
 
   /**
    * @param callFactory A {@link Call.Factory} (typically an {@link okhttp3.OkHttpClient}) for use
    *     by the source.
-   * @param userAgent An optional User-Agent string that should be used.
+   * @param userAgent An optional User-Agent string.
    * @param contentTypePredicate An optional {@link Predicate}. If a content type is rejected by the
    *     predicate then a {@link InvalidContentTypeException} is thrown from
    *     {@link #open(DataSpec)}.
    * @param listener An optional listener.
    */
-  public OkHttpDataSource(Call.Factory callFactory, @Nullable String userAgent,
-      Predicate<String> contentTypePredicate, TransferListener<? super OkHttpDataSource> listener) {
+  public OkHttpDataSource(@NonNull Call.Factory callFactory, @Nullable String userAgent,
+      @Nullable Predicate<String> contentTypePredicate,
+      @Nullable TransferListener<? super OkHttpDataSource> listener) {
     this(callFactory, userAgent, contentTypePredicate, listener, null, null);
   }
 
   /**
    * @param callFactory A {@link Call.Factory} (typically an {@link okhttp3.OkHttpClient}) for use
    *     by the source.
-   * @param userAgent An optional User-Agent string that should be used.
+   * @param userAgent An optional User-Agent string.
    * @param contentTypePredicate An optional {@link Predicate}. If a content type is rejected by the
    *     predicate then a {@link InvalidContentTypeException} is thrown from
    *     {@link #open(DataSpec)}.
@@ -104,9 +106,10 @@ public class OkHttpDataSource implements HttpDataSource {
    * @param defaultRequestProperties The optional default {@link RequestProperties} to be sent to
    *    the server as HTTP headers on every request.
    */
-  public OkHttpDataSource(Call.Factory callFactory, @Nullable String userAgent,
-      Predicate<String> contentTypePredicate, TransferListener<? super OkHttpDataSource> listener,
-      CacheControl cacheControl, RequestProperties defaultRequestProperties) {
+  public OkHttpDataSource(@NonNull Call.Factory callFactory, @Nullable String userAgent,
+      @Nullable Predicate<String> contentTypePredicate,
+      @Nullable TransferListener<? super OkHttpDataSource> listener,
+      @Nullable CacheControl cacheControl, @Nullable RequestProperties defaultRequestProperties) {
     this.callFactory = Assertions.checkNotNull(callFactory);
     this.userAgent = userAgent;
     this.contentTypePredicate = contentTypePredicate;
diff --git a/extensions/okhttp/src/main/java/com/google/android/exoplayer2/ext/okhttp/OkHttpDataSourceFactory.java b/extensions/okhttp/src/main/java/com/google/android/exoplayer2/ext/okhttp/OkHttpDataSourceFactory.java
index 6ee09df7de..32fc5a58cb 100644
--- a/extensions/okhttp/src/main/java/com/google/android/exoplayer2/ext/okhttp/OkHttpDataSourceFactory.java
+++ b/extensions/okhttp/src/main/java/com/google/android/exoplayer2/ext/okhttp/OkHttpDataSourceFactory.java
@@ -15,8 +15,8 @@
  */
 package com.google.android.exoplayer2.ext.okhttp;
 
+import android.support.annotation.NonNull;
 import android.support.annotation.Nullable;
-
 import com.google.android.exoplayer2.upstream.DataSource;
 import com.google.android.exoplayer2.upstream.HttpDataSource;
 import com.google.android.exoplayer2.upstream.HttpDataSource.BaseFactory;
@@ -30,32 +30,32 @@ import okhttp3.Call;
  */
 public final class OkHttpDataSourceFactory extends BaseFactory {
 
-  private final Call.Factory callFactory;
-  private final String userAgent;
-  private final TransferListener<? super DataSource> listener;
-  private final CacheControl cacheControl;
+  @NonNull private final Call.Factory callFactory;
+  @Nullable private final String userAgent;
+  @Nullable private final TransferListener<? super DataSource> listener;
+  @Nullable private final CacheControl cacheControl;
 
   /**
    * @param callFactory A {@link Call.Factory} (typically an {@link okhttp3.OkHttpClient}) for use
    *     by the sources created by the factory.
-   * @param userAgent An optional User-Agent string that should be used.
+   * @param userAgent An optional User-Agent string.
    * @param listener An optional listener.
    */
-  public OkHttpDataSourceFactory(Call.Factory callFactory, @Nullable String userAgent,
-      TransferListener<? super DataSource> listener) {
+  public OkHttpDataSourceFactory(@NonNull Call.Factory callFactory, @Nullable String userAgent,
+      @Nullable TransferListener<? super DataSource> listener) {
     this(callFactory, userAgent, listener, null);
   }
 
   /**
    * @param callFactory A {@link Call.Factory} (typically an {@link okhttp3.OkHttpClient}) for use
    *     by the sources created by the factory.
-   * @param userAgent An optional User-Agent string that should be used.
+   * @param userAgent An optional User-Agent string.
    * @param listener An optional listener.
    * @param cacheControl An optional {@link CacheControl} for setting the Cache-Control header.
    */
-  public OkHttpDataSourceFactory(Call.Factory callFactory,
-                                 @Nullable String userAgent,
-      TransferListener<? super DataSource> listener, CacheControl cacheControl) {
+  public OkHttpDataSourceFactory(@NonNull Call.Factory callFactory, @Nullable String userAgent,
+      @Nullable TransferListener<? super DataSource> listener,
+      @Nullable CacheControl cacheControl) {
     this.callFactory = callFactory;
     this.userAgent = userAgent;
     this.listener = listener;