[android] Update toGeoJSON in android_conversion.hpp (#16243)

* [android] Update toGeoJSON in android_conversion.hpp

* Fix review comments

* Update android_conversion.hpp

2 files changed, 28 insertions, 2 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2ae4d91137..9f829790d7 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,6 +10,12 @@
 
 - [default] Fix possible crash at RunLoop::wake() ([#16255](https://github.com/mapbox/mapbox-gl-native/pull/16255))
 
+- [android] Update toGeoJSON in android_conversion.hpp [#16243](https://github.com/mapbox/mapbox-gl-native/pull/16243)
+  
+  Before this chage, `toGeoJSON` method in `android_conversion.hpp` can't convert Object(Map in android) to GeoJSON object. 
+  
+  But `within` expression need to accept an Object and then convert to GeoJSON object, now `toGeoJSON` method can convert both string and Object to GeoJSON.
+ 
 ## maps-v1.3.0 (2020.02-relvanillashake)
 
 ### 🐞 Bug fixes
diff --git a/platform/android/src/style/android_conversion.hpp b/platform/android/src/style/android_conversion.hpp
index dc0a0acb31..6f16804597 100644
--- a/platform/android/src/style/android_conversion.hpp
+++ b/platform/android/src/style/android_conversion.hpp
@@ -110,11 +110,31 @@ public:
     }
 
     static optional<GeoJSON> toGeoJSON(const mbgl::android::Value &value, Error &error) {
-        if (value.isNull() || !value.isString()) {
+        if (value.isNull()) {
             error = { "no json data found" };
             return {};
         }
-        return parseGeoJSON(value.toString(), error);
+
+        if (value.isString()) {
+            return parseGeoJSON(value.toString(), error);
+        }
+
+        if (value.isObject()) {
+            mbgl::android::Value keys = value.keyArray();
+            std::size_t length = arrayLength(keys);
+            for (std::size_t i = 0; i < length; ++i) {
+                if (keys.get(i).toString() == "json") {
+                    auto v = value.get("json");
+                    if (v.isString()) {
+                        return parseGeoJSON(v.toString(), error);
+                    } else {
+                        break;
+                    }
+                }
+            }
+        }
+        error = {"no json data found"};
+        return {};
     }
 };