[android] fix source ownership

platform/android/MapboxGLAndroidSDK/src/main/java/com/mapbox/mapboxsdk/style/sources/CannotAddSourceException.java

@@ -0,0 +1,12 @@
+package com.mapbox.mapboxsdk.style.sources;
+
+/**
+ * Thrown when adding a source to a map twice
+ */
+public class CannotAddSourceException extends RuntimeException {
+
+    public CannotAddSourceException(String message) {
+        super(message);
+    }
+
+}

platform/android/src/jni.cpp

@@ -1142,9 +1142,13 @@ void nativeAddSource(JNIEnv *env, jni::jobject* obj, jni::jlong nativeMapViewPtr
     assert(nativeSourcePtr != 0);
 
     NativeMapView *nativeMapView = reinterpret_cast<NativeMapView *>(nativeMapViewPtr);
-    Source *source = reinterpret_cast<Source *>(nativeSourcePtr);
 
-    nativeMapView->getMap().addSource(source->releaseCoreSource());
+    Source *source = reinterpret_cast<Source *>(nativeSourcePtr);
+    try {
+        source->addToMap(nativeMapView->getMap());
+    } catch (const std::runtime_error& error) {
+        jni::ThrowNew(*env, jni::FindClass(*env, "com/mapbox/mapboxsdk/style/sources/CannotAddSourceException"), error.what());
+    }
 }
 
 void nativeRemoveSource(JNIEnv *env, jni::jobject* obj, jlong nativeMapViewPtr, jni::jstring* id) {

platform/android/src/style/sources/source.cpp

@@ -35,6 +35,19 @@ namespace android {
         return jni::Make<jni::String>(env, source.getID());
     }
 
+    void Source::addToMap(mbgl::Map& _map) {
+        //Check to see if we own the source first
+        if (!ownedSource) {
+            throw std::runtime_error("Cannot add source twice");
+        }
+
+        //Add source to map
+        _map.addSource(releaseCoreSource());
+
+        //Save pointer to the map
+        this->map = &_map;
+    }
+
     std::unique_ptr<mbgl::style::Source> Source::releaseCoreSource() {
         assert(ownedSource != nullptr);
         return std::move(ownedSource);

platform/android/src/style/sources/source.hpp

@@ -32,16 +32,23 @@ public:
 
     virtual ~Source();
 
+    void addToMap(mbgl::Map&);
+
     virtual jni::jobject* createJavaPeer(jni::JNIEnv&) = 0;
 
     jni::String getId(jni::JNIEnv&);
 
+protected:
     //Release the owned view and return it
     std::unique_ptr<mbgl::style::Source> releaseCoreSource();
 
-protected:
+    //Set on newly created sources until added to the map
     std::unique_ptr<mbgl::style::Source> ownedSource;
+
+    //Raw pointer that is valid until the source is removed from the map
     mbgl::style::Source& source;
+
+    //Map pointer is valid for newly created sources only after adding to the map
     mbgl::Map* map;
 };