feat(fcm): Add image in notification support.

src/main/java/com/google/firebase/messaging/AndroidNotification.java

@@ -66,6 +66,9 @@ public class AndroidNotification {
 
   @Key("channel_id")
   private final String channelId;
+
+  @Key("image")
+  private final String image;
 
   private AndroidNotification(Builder builder) {
     this.title = builder.title;
@@ -97,6 +100,7 @@ private AndroidNotification(Builder builder) {
       this.titleLocArgs = null;
     }
     this.channelId = builder.channelId;
+    this.image = builder.image;
   }
 
   /**
@@ -122,6 +126,7 @@ public static class Builder {
     private String titleLocKey;
     private List<String> titleLocArgs = new ArrayList<>();
     private String channelId;
+    private String image;
 
     private Builder() {}
 
@@ -292,6 +297,18 @@ public Builder setChannelId(String channelId) {
       return this;
     }
 
+    /**
+     * Sets the URL of the image that is going to be displayed in the notification. When provided, 
+     * overrides the imageUrl set via {@link Notification}.
+     *
+     * @param imageUrl URL of the image that is going to be displayed in the notification.
+     * @return This builder.
+     */
+    public Builder setImage(String imageUrl) {
+      this.image = imageUrl;
+      return this;
+    }
+
     /**
      * Creates a new {@link AndroidNotification} instance from the parameters set on this builder.
      *

src/main/java/com/google/firebase/messaging/ApnsFcmOptions.java

@@ -24,10 +24,14 @@ public final class ApnsFcmOptions {
 
   @Key("analytics_label")
   private final String analyticsLabel;
+
+  @Key("image")
+  private final String image;
 
   private ApnsFcmOptions(Builder builder) {
     FcmOptionsUtil.checkAnalyticsLabel(builder.analyticsLabel);
     this.analyticsLabel = builder.analyticsLabel;
+    this.image = builder.image;
   }
 
   /**
@@ -53,6 +57,8 @@ public static class Builder {
 
     private String analyticsLabel;
 
+    private String image;
+
     private Builder() {}
 
     /**
@@ -64,6 +70,15 @@ public Builder setAnalyticsLabel(String analyticsLabel) {
       return this;
     }
 
+    /**
+     * @param imageUrl URL of the image that is going to be displayed in the notification.
+     * @return This builder
+     */
+    public Builder setImage(String imageUrl) {
+      this.image = imageUrl;
+      return this;
+    }
+
     /**
      * Creates a new {@link ApnsFcmOptions} instance from the parameters set on this builder.
      *

src/main/java/com/google/firebase/messaging/Notification.java

@@ -29,6 +29,9 @@ public class Notification {
 
   @Key("body")
   private final String body;
+
+  @Key("image")
+  private final String image;
 
   /**
    * Creates a new {@code Notification} using the given title and body.
@@ -37,8 +40,20 @@ public class Notification {
    * @param body Body of the notification.
    */
   public Notification(String title, String body) {
+    this(title, body, null);
+  }
+
+  /**
+   * Creates a new {@code Notification} using the given title, body, and image.
+   *
+   * @param title Title of the notification.
+   * @param body Body of the notification.
+   * @param imageUrl URL of the image that is going to be displayed in the notification.
+   */
+  public Notification(String title, String body, String imageUrl) {
     this.title = title;
     this.body = body;
+    this.image = imageUrl;
   }
 
 }

src/test/java/com/google/firebase/messaging/FirebaseMessagingIT.java

@@ -34,6 +34,7 @@ public class FirebaseMessagingIT {
   private static final String TEST_REGISTRATION_TOKEN =
       "fGw0qy4TGgk:APA91bGtWGjuhp4WRhHXgbabIYp1jxEKI08ofj_v1bKhWAGJQ4e3arRCWzeTfHaLz83mBnDh0a"
           + "PWB1AykXAVUUGl2h1wT4XI6XazWpvY7RBUSYfoxtqSWGIm2nvWh2BOP1YG501SsRoE";
+  private static final String TEST_IMAGE_URL = "https://example.com/image.png";
 
   @BeforeClass
   public static void setUpClass() {
@@ -44,7 +45,7 @@ public static void setUpClass() {
   public void testSend() throws Exception {
     FirebaseMessaging messaging = FirebaseMessaging.getInstance();
     Message message = Message.builder()
-        .setNotification(new Notification("Title", "Body"))
+        .setNotification(new Notification("Title", "Body", TEST_IMAGE_URL))
         .setAndroidConfig(AndroidConfig.builder()
             .setRestrictedPackageName("com.google.firebase.testing")
             .build())

src/test/java/com/google/firebase/messaging/MessageTest.java

@@ -36,6 +36,10 @@
 
 public class MessageTest {
 
+  private static final String TEST_IMAGE_URL = "https://example.com/image.png";
+  private static final String TEST_IMAGE_URL_ANDROID = "https://example.com/android-image.png";
+  private static final String TEST_IMAGE_URL_APNS = "https://example.com/apns-image.png";
+
   @Test(expected = IllegalArgumentException.class)
   public void testMessageWithoutTarget() {
     Message.builder().build();
@@ -678,6 +682,76 @@ public void testIncorrectAnalyticsLabelFormat() {
     }
   }
 
+  @Test
+  public void testImageInNotification() throws IOException {
+    Message message = Message.builder()
+        .setNotification(new Notification("title", "body", TEST_IMAGE_URL))
+        .setTopic("test-topic")
+        .build();
+    Map<String, String> data = ImmutableMap.of(
+        "title", "title", "body", "body", "image", TEST_IMAGE_URL);
+    assertJsonEquals(ImmutableMap.of("topic", "test-topic", "notification", data), message);
+  }
+
+  @Test
+  public void testImageInAndroidNotification() throws IOException {
+    Message message = Message.builder()
+        .setNotification(new Notification("title", "body", TEST_IMAGE_URL))
+        .setAndroidConfig(AndroidConfig.builder()
+            .setNotification(AndroidNotification.builder()
+                .setTitle("android-title")
+                .setBody("android-body")
+                .setImage(TEST_IMAGE_URL_ANDROID)
+                .build())
+            .build())
+        .setTopic("test-topic")
+        .build();
+    Map<String, Object> notification = ImmutableMap.<String, Object>builder()
+        .put("title", "title")
+        .put("body", "body")
+        .put("image", TEST_IMAGE_URL)
+        .build();
+    Map<String, Object> androidConfig = ImmutableMap.<String, Object>builder()
+        .put("notification", ImmutableMap.<String, Object>builder()
+            .put("title", "android-title")
+            .put("body", "android-body")
+            .put("image", TEST_IMAGE_URL_ANDROID)
+            .build())
+        .build();
+    assertJsonEquals(ImmutableMap.of(
+        "topic", "test-topic", "notification", notification, "android", androidConfig), message);
+  }
+
+  @Test
+  public void testImageInApnsNotification() throws IOException {
+    Message message = Message.builder()
+        .setTopic("test-topic")
+        .setNotification(new Notification("title", "body", TEST_IMAGE_URL))
+        .setApnsConfig(
+            ApnsConfig.builder().setAps(Aps.builder().build())
+                .setFcmOptions(ApnsFcmOptions.builder().setImage(TEST_IMAGE_URL_APNS).build())
+                .build()).build();
+
+    ImmutableMap<String, Object> notification =
+        ImmutableMap.<String, Object>builder()
+            .put("title", "title")
+            .put("body", "body")
+            .put("image", TEST_IMAGE_URL)
+            .build();
+    ImmutableMap<String, Object> apnsConfig =
+        ImmutableMap.<String, Object>builder()
+            .put("fcm_options", ImmutableMap.of("image", TEST_IMAGE_URL_APNS))
+            .put("payload", ImmutableMap.of("aps", ImmutableMap.of()))
+            .build();
+    ImmutableMap<String, Object> expected =
+        ImmutableMap.<String, Object>builder()
+            .put("topic", "test-topic")
+            .put("notification", notification)
+            .put("apns", apnsConfig)
+            .build();
+    assertJsonEquals(expected, message);
+  }
+
   private static void assertJsonEquals(
       Map expected, Object actual) throws IOException {
     assertEquals(expected, toMap(actual));