1 files changed, 29 insertions, 29 deletions

diff --git a/platform/android/src/file_source.cpp b/platform/android/src/file_source.cpp
index 2a6cac3b02..d9b8e12dc4 100644
--- a/platform/android/src/file_source.cpp
+++ b/platform/android/src/file_source.cpp
@@ -1,4 +1,5 @@
 #include "file_source.hpp"
+#include "attach_env.hpp"
 
 #include <mbgl/actor/actor.hpp>
 #include <mbgl/actor/scheduler.hpp>
@@ -6,7 +7,6 @@
 #include <mbgl/util/logging.hpp>
 
 #include "asset_manager_file_source.hpp"
-#include "jni/generic_global_ref_deleter.hpp"
 
 namespace mbgl {
 namespace android {
@@ -14,9 +14,9 @@ namespace android {
 // FileSource //
 
 FileSource::FileSource(jni::JNIEnv& _env,
-                       jni::String accessToken,
-                       jni::String _cachePath,
-                       jni::Object<AssetManager> assetManager) {
+                       const jni::String& accessToken,
+                       const jni::String& _cachePath,
+                       const jni::Object<AssetManager>& assetManager) {
     // Create a core default file source
     fileSource = std::make_unique<mbgl::DefaultFileSource>(
         jni::Make<std::string>(_env, _cachePath) + "/mbgl-offline.db",
@@ -31,30 +31,31 @@ FileSource::FileSource(jni::JNIEnv& _env,
 FileSource::~FileSource() {
 }
 
-jni::String FileSource::getAccessToken(jni::JNIEnv& env) {
+jni::Local<jni::String> FileSource::getAccessToken(jni::JNIEnv& env) {
     return jni::Make<jni::String>(env, fileSource->getAccessToken());
 }
 
-void FileSource::setAccessToken(jni::JNIEnv& env, jni::String token) {
+void FileSource::setAccessToken(jni::JNIEnv& env, const jni::String& token) {
     fileSource->setAccessToken(jni::Make<std::string>(env, token));
 }
 
-void FileSource::setAPIBaseUrl(jni::JNIEnv& env, jni::String url) {
+void FileSource::setAPIBaseUrl(jni::JNIEnv& env, const jni::String& url) {
     fileSource->setAPIBaseURL(jni::Make<std::string>(env, url));
 }
 
-void FileSource::setResourceTransform(jni::JNIEnv& env, jni::Object<FileSource::ResourceTransformCallback> transformCallback) {
+void FileSource::setResourceTransform(jni::JNIEnv& env, const jni::Object<FileSource::ResourceTransformCallback>& transformCallback) {
     if (transformCallback) {
+        auto global = jni::NewGlobal<jni::EnvAttachingDeleter>(env, transformCallback);
         resourceTransform = std::make_unique<Actor<ResourceTransform>>(*Scheduler::GetCurrent(),
             // Capture the ResourceTransformCallback object as a managed global into
             // the lambda. It is released automatically when we're setting a new ResourceTransform in
             // a subsequent call.
             // Note: we're converting it to shared_ptr because this lambda is converted to a std::function,
             // which requires copyability of its captured variables.
-            [callback = std::shared_ptr<jni::jobject>(transformCallback.NewGlobalRef(env).release()->Get(), GenericGlobalRefDeleter())]
+            [callback = std::make_shared<decltype(global)>(std::move(global))]
             (mbgl::Resource::Kind kind, const std::string&& url_) {
                 android::UniqueEnv _env = android::AttachEnv();
-                return FileSource::ResourceTransformCallback::onURL(*_env, jni::Object<FileSource::ResourceTransformCallback>(*callback), int(kind), url_);
+                return FileSource::ResourceTransformCallback::onURL(*_env, *callback, int(kind), url_);
             });
         fileSource->setResourceTransform(resourceTransform->self());
     } else {
@@ -92,30 +93,32 @@ jni::jboolean FileSource::isResumed(jni::JNIEnv&) {
     return (jboolean) false;
 }
 
-jni::Class<FileSource> FileSource::javaClass;
-
-FileSource* FileSource::getNativePeer(jni::JNIEnv& env, jni::Object<FileSource> jFileSource) {
-    static auto field = FileSource::javaClass.GetField<jlong>(env, "nativePtr");
+FileSource* FileSource::getNativePeer(jni::JNIEnv& env, const jni::Object<FileSource>& jFileSource) {
+    static auto& javaClass = jni::Class<FileSource>::Singleton(env);
+    static auto field = javaClass.GetField<jlong>(env, "nativePtr");
     return reinterpret_cast<FileSource *>(jFileSource.Get(env, field));
 }
 
-mbgl::DefaultFileSource& FileSource::getDefaultFileSource(jni::JNIEnv& env, jni::Object<FileSource> jFileSource) {
+mbgl::DefaultFileSource& FileSource::getDefaultFileSource(jni::JNIEnv& env, const jni::Object<FileSource>& jFileSource) {
     FileSource* fileSource = FileSource::getNativePeer(env, jFileSource);
     assert(fileSource != nullptr);
     return *fileSource->fileSource;
 }
 
 void FileSource::registerNative(jni::JNIEnv& env) {
-    //Register classes
-    FileSource::javaClass = *jni::Class<FileSource>::Find(env).NewGlobalRef(env).release();
-    FileSource::ResourceTransformCallback::javaClass = *jni::Class<FileSource::ResourceTransformCallback>::Find(env).NewGlobalRef(env).release();
+    // Ensure the class for ResourceTransformCallback is cached. If it's requested for the
+    // first time on a background thread, Android's class loader heuristics will fail.
+    // https://developer.android.com/training/articles/perf-jni#faq_FindClass
+    jni::Class<ResourceTransformCallback>::Singleton(env);
+
+    static auto& javaClass = jni::Class<FileSource>::Singleton(env);
 
     #define METHOD(MethodPtr, name) jni::MakeNativePeerMethod<decltype(MethodPtr), (MethodPtr)>(name)
 
     // Register the peer
     jni::RegisterNativePeer<FileSource>(
-        env, FileSource::javaClass, "nativePtr",
-        std::make_unique<FileSource, JNIEnv&, jni::String, jni::String, jni::Object<AssetManager>>,
+        env, javaClass, "nativePtr",
+        jni::MakePeer<FileSource, const jni::String&, const jni::String&, const jni::Object<AssetManager>&>,
         "initialize",
         "finalize",
         METHOD(&FileSource::getAccessToken, "getAccessToken"),
@@ -131,16 +134,13 @@ void FileSource::registerNative(jni::JNIEnv& env) {
 
 // FileSource::ResourceTransformCallback //
 
-jni::Class<FileSource::ResourceTransformCallback> FileSource::ResourceTransformCallback::javaClass;
-
-std::string FileSource::ResourceTransformCallback::onURL(jni::JNIEnv& env, jni::Object<FileSource::ResourceTransformCallback> callback, int kind, std::string url_) {
-    static auto method = FileSource::ResourceTransformCallback::javaClass.GetMethod<jni::String (jni::jint, jni::String)>(env, "onURL");
-    auto url = jni::Make<jni::String>(env, url_);
+std::string FileSource::ResourceTransformCallback::onURL(jni::JNIEnv& env, const jni::Object<FileSource::ResourceTransformCallback>& callback, int kind, std::string url_) {
+    static auto& javaClass = jni::Class<FileSource::ResourceTransformCallback>::Singleton(env);
+    static auto method = javaClass.GetMethod<jni::String (jni::jint, jni::String)>(env, "onURL");
 
-    url = callback.Call(env, method, kind, url);
-    auto urlStr = jni::Make<std::string>(env, url);
-    jni::DeleteLocalRef(env, url);
-    return urlStr;
+    return jni::Make<std::string>(env,
+        callback.Call(env, method, kind,
+            jni::Make<jni::String>(env, url_)));
 }
 
 } // namespace android