[android] Move conversion code to .cpp files

platform/android/src/conversion/collection.cpp

@@ -0,0 +1,38 @@
+#include "collection.hpp"
+#include "constant.hpp"
+
+namespace mbgl {
+namespace android {
+namespace conversion {
+
+std::vector<std::string> toVector(JNIEnv& env, jni::jarray<jni::jobject>& array) {
+    std::vector<std::string> vector;
+    std::size_t len = jni::GetArrayLength(env, array);
+    vector.reserve(len);
+
+    for (std::size_t i = 0; i < len; i++) {
+        jni::jstring* jstr = reinterpret_cast<jni::jstring*>(jni::GetObjectArrayElement(env, array, i));
+        vector.push_back(*convert<std::string, jni::String>(env, jni::String(jstr)));
+        jni::DeleteLocalRef(env, jstr);
+    }
+
+    return vector;
+}
+
+std::vector<std::string> toVector(JNIEnv& env, jni::Array<jni::String> array) {
+    std::size_t len = array.Length(env);
+    std::vector<std::string> vector;
+    vector.reserve(len);
+
+    for (std::size_t i = 0; i < len; i++) {
+        jni::String jstr = array.Get(env, i);
+        vector.push_back(*convert<std::string, jni::String>(env, jstr));
+        jni::DeleteLocalRef(env, jstr);
+    }
+
+    return vector;
+}
+
+}
+}
+}