diff --git a/android/common/CallbackUtils.cpp b/android/common/CallbackUtils.cpp
index 2ef64e144e..d9a5151990 100644
--- a/android/common/CallbackUtils.cpp
+++ b/android/common/CallbackUtils.cpp
@@ -16,6 +16,8 @@
 
 #include "CallbackUtils.h"
 
+#include "private/backend/VirtualMachineEnv.h"
+
 void acquireCallbackJni(JNIEnv* env, CallbackJni& callbackUtils) {
 #ifdef ANDROID
     callbackUtils.handlerClass = env->FindClass("android/os/Handler");
@@ -49,53 +51,6 @@ void releaseCallbackJni(JNIEnv* env, CallbackJni callbackUtils, jobject handler,
     env->DeleteGlobalRef(callbackUtils.executorClass);
 }
 
-JniBufferCallback* JniBufferCallback::make(filament::Engine* engine,
-        JNIEnv* env, jobject handler, jobject callback, AutoBuffer&& buffer) {
-    return new JniBufferCallback(env, handler, callback, std::move(buffer));
-}
-
-JniBufferCallback::JniBufferCallback(JNIEnv* env, jobject handler, jobject callback,
-        AutoBuffer&& buffer)
-        : mEnv(env)
-        , mHandler(env->NewGlobalRef(handler))
-        , mCallback(env->NewGlobalRef(callback))
-        , mBuffer(std::move(buffer)) {
-    acquireCallbackJni(env, mCallbackUtils);
-}
-
-JniBufferCallback::~JniBufferCallback() {
-    releaseCallbackJni(mEnv, mCallbackUtils, mHandler, mCallback);
-}
-
-void JniBufferCallback::invoke(void*, size_t, void* user) {
-    JniBufferCallback* data = reinterpret_cast<JniBufferCallback*>(user);
-    delete data;
-}
-
-// -----------------------------------------------------------------------------------------------
-
-JniImageCallback* JniImageCallback::make(filament::Engine* engine,
-        JNIEnv* env, jobject handler, jobject callback, long image) {
-    return new JniImageCallback(env, handler, callback, image);
-}
-
-JniImageCallback::JniImageCallback(JNIEnv* env, jobject handler, jobject callback, long image)
-        : mEnv(env)
-        , mHandler(env->NewGlobalRef(handler))
-        , mCallback(env->NewGlobalRef(callback))
-        , mImage(image) {
-    acquireCallbackJni(env, mCallbackUtils);
-}
-
-JniImageCallback::~JniImageCallback() {
-    releaseCallbackJni(mEnv, mCallbackUtils, mHandler, mCallback);
-}
-
-void JniImageCallback::invoke(void*, void* user) {
-    JniImageCallback* data = reinterpret_cast<JniImageCallback*>(user);
-    delete data;
-}
-
 // -----------------------------------------------------------------------------------------------
 
 JniCallback* JniCallback::make(JNIEnv* env, jobject handler, jobject callback) {
@@ -103,17 +58,65 @@ JniCallback* JniCallback::make(JNIEnv* env, jobject handler, jobject callback) {
 }
 
 JniCallback::JniCallback(JNIEnv* env, jobject handler, jobject callback)
-        : mEnv(env)
-        , mHandler(env->NewGlobalRef(handler))
-        , mCallback(env->NewGlobalRef(callback)) {
+        : mHandler(env->NewGlobalRef(handler)),
+          mCallback(env->NewGlobalRef(callback)) {
     acquireCallbackJni(env, mCallbackUtils);
 }
 
-JniCallback::~JniCallback() {
-    releaseCallbackJni(mEnv, mCallbackUtils, mHandler, mCallback);
+JniCallback::~JniCallback() = default;
+
+void JniCallback::post(void* user, filament::backend::CallbackHandler::Callback callback) {
+    callback(user);
 }
 
-void JniCallback::invoke(void* user) {
-    JniCallback* data = reinterpret_cast<JniCallback*>(user);
-    delete data;
+void JniCallback::postToJavaAndDestroy(JniCallback* callback) {
+    JNIEnv* env = filament::VirtualMachineEnv::get().getEnvironment();
+    releaseCallbackJni(env, callback->mCallbackUtils, callback->mHandler, callback->mCallback);
+    delete callback;
+}
+
+// -----------------------------------------------------------------------------------------------
+
+JniBufferCallback* JniBufferCallback::make(filament::Engine*,
+        JNIEnv* env, jobject handler, jobject callback, AutoBuffer&& buffer) {
+    return new JniBufferCallback(env, handler, callback, std::move(buffer));
+}
+
+JniBufferCallback::JniBufferCallback(JNIEnv* env, jobject handler, jobject callback,
+        AutoBuffer&& buffer)
+        : JniCallback(env, handler, callback),
+        mBuffer(std::move(buffer)) {
+    acquireCallbackJni(env, mCallbackUtils);
+}
+
+JniBufferCallback::~JniBufferCallback() = default;
+
+void JniBufferCallback::postToJavaAndDestroy(void*, size_t, void* user) {
+    JniBufferCallback* callback = (JniBufferCallback*)user;
+    JNIEnv* env = filament::VirtualMachineEnv::get().getEnvironment();
+    callback->mBuffer.attachToJniThread(env);
+    releaseCallbackJni(env, callback->mCallbackUtils, callback->mHandler, callback->mCallback);
+    delete callback;
+}
+
+// -----------------------------------------------------------------------------------------------
+
+JniImageCallback* JniImageCallback::make(filament::Engine*,
+        JNIEnv* env, jobject handler, jobject callback, long image) {
+    return new JniImageCallback(env, handler, callback, image);
+}
+
+JniImageCallback::JniImageCallback(JNIEnv* env, jobject handler, jobject callback, long image)
+        : JniCallback(env, handler, callback),
+        mImage(image) {
+    acquireCallbackJni(env, mCallbackUtils);
+}
+
+JniImageCallback::~JniImageCallback() = default;
+
+void JniImageCallback::postToJavaAndDestroy(void*, void* user) {
+    JniImageCallback* callback = (JniImageCallback*)user;
+    JNIEnv* env = filament::VirtualMachineEnv::get().getEnvironment();
+    releaseCallbackJni(env, callback->mCallbackUtils, callback->mHandler, callback->mCallback);
+    delete callback;
 }
diff --git a/android/common/CallbackUtils.h b/android/common/CallbackUtils.h
index 6a631efe5c..93e3c7ec0f 100644
--- a/android/common/CallbackUtils.h
+++ b/android/common/CallbackUtils.h
@@ -18,9 +18,10 @@
 
 #include <jni.h>
 
-#include "common/CallbackUtils.h"
 #include "common/NioUtils.h"
 
+#include <backend/CallbackHandler.h>
+
 #include <filament/Engine.h>
 
 struct CallbackJni {
@@ -35,60 +36,49 @@ struct CallbackJni {
 void acquireCallbackJni(JNIEnv* env, CallbackJni& callbackUtils);
 void releaseCallbackJni(JNIEnv* env, CallbackJni callbackUtils, jobject handler, jobject callback);
 
-struct JniBufferCallback {
+struct JniCallback : private filament::backend::CallbackHandler {
+    JniCallback(JniCallback const &) = delete;
+    JniCallback(JniCallback&&) = delete;
+
+    static JniCallback* make(JNIEnv* env, jobject handler, jobject runnable);
+
+    static void postToJavaAndDestroy(JniCallback* callback);
+
+    void post(void* user, Callback callback) override;
+
+    filament::backend::CallbackHandler* getHandler() noexcept { return this; }
+
+    jobject getCallbackObject() { return mCallback; }
+
+protected:
+    JniCallback(JNIEnv* env, jobject handler, jobject runnable);
+    virtual ~JniCallback();
+    jobject mHandler;
+    jobject mCallback;
+    CallbackJni mCallbackUtils;
+};
+
+
+struct JniBufferCallback : public JniCallback {
     static JniBufferCallback* make(filament::Engine* engine,
             JNIEnv* env, jobject handler, jobject callback, AutoBuffer&& buffer);
 
-    static void invoke(void* buffer, size_t n, void* user);
+    static void postToJavaAndDestroy(void*, size_t, void* user);
 
 private:
     JniBufferCallback(JNIEnv* env, jobject handler, jobject callback, AutoBuffer&& buffer);
-    JniBufferCallback(JniBufferCallback const &) = delete;
-    JniBufferCallback(JniBufferCallback&&) = delete;
-    ~JniBufferCallback();
-
-    JNIEnv* mEnv;
-    jobject mHandler;
-    jobject mCallback;
+    virtual ~JniBufferCallback();
     AutoBuffer mBuffer;
-    CallbackJni mCallbackUtils;
 };
 
-struct JniImageCallback {
+struct JniImageCallback : public JniCallback {
     static JniImageCallback* make(filament::Engine* engine, JNIEnv* env, jobject handler,
             jobject runnable, long image);
 
-    static void invoke(void* image, void* user);
+    static void postToJavaAndDestroy(void*, void* user);
 
 private:
     JniImageCallback(JNIEnv* env, jobject handler, jobject runnable, long image);
-    JniImageCallback(JniImageCallback const &) = delete;
-    JniImageCallback(JniImageCallback&&) = delete;
-    ~JniImageCallback();
-
-    JNIEnv* mEnv;
-    jobject mHandler;
-    jobject mCallback;
+    virtual ~JniImageCallback();
     long mImage;
-    CallbackJni mCallbackUtils;
-};
-
-struct JniCallback {
-    static JniCallback* make(JNIEnv* env, jobject handler, jobject runnable);
-
-    static void invoke(void* user);
-
-    jobject getCallbackObject() { return mCallback; }
-    JNIEnv* getJniEnv() { return mEnv; }
-
-private:
-    JniCallback(JNIEnv* env, jobject handler, jobject runnable);
-    JniCallback(JniCallback const &) = delete;
-    JniCallback(JniCallback&&) = delete;
-    ~JniCallback();
-
-    JNIEnv* mEnv;
-    jobject mHandler;
-    jobject mCallback;
-    CallbackJni mCallbackUtils;
 };
diff --git a/android/common/NioUtils.h b/android/common/NioUtils.h
index 94e43d92e3..72f4656ea9 100644
--- a/android/common/NioUtils.h
+++ b/android/common/NioUtils.h
@@ -38,6 +38,10 @@ public:
     AutoBuffer(AutoBuffer&& rhs) noexcept;
     ~AutoBuffer() noexcept;
 
+    void attachToJniThread(JNIEnv* env) noexcept {
+        mEnv = env;
+    }
+
     void* getData() const noexcept {
         return mUserData;
     }
diff --git a/android/filament-android/CMakeLists.txt b/android/filament-android/CMakeLists.txt
index cdf4c7511d..df4ea3cbdc 100644
--- a/android/filament-android/CMakeLists.txt
+++ b/android/filament-android/CMakeLists.txt
@@ -125,6 +125,7 @@ target_link_libraries(filament-jni
 target_include_directories(filament-jni PRIVATE
         ..
         ${FILAMENT_DIR}/include
+        ../../filament/backend/include
         ../../third_party/robin-map
         ../../libs/utils/include)
 
diff --git a/android/filament-android/src/main/cpp/BufferObject.cpp b/android/filament-android/src/main/cpp/BufferObject.cpp
index e86d81bd5c..cdb4c39694 100644
--- a/android/filament-android/src/main/cpp/BufferObject.cpp
+++ b/android/filament-android/src/main/cpp/BufferObject.cpp
@@ -91,7 +91,8 @@ Java_com_google_android_filament_BufferObject_nSetBuffer(JNIEnv *env, jclass typ
 
     auto* callback = JniBufferCallback::make(engine, env, handler, runnable, std::move(nioBuffer));
 
-    BufferDescriptor desc(data, sizeInBytes, &JniBufferCallback::invoke, callback);
+    BufferDescriptor desc(data, sizeInBytes,
+            callback->getHandler(), &JniBufferCallback::postToJavaAndDestroy, callback);
 
     bufferObject->setBuffer(*engine, std::move(desc), (uint32_t) destOffsetInBytes);
 
diff --git a/android/filament-android/src/main/cpp/IndexBuffer.cpp b/android/filament-android/src/main/cpp/IndexBuffer.cpp
index 86515e7485..f88f95fd6a 100644
--- a/android/filament-android/src/main/cpp/IndexBuffer.cpp
+++ b/android/filament-android/src/main/cpp/IndexBuffer.cpp
@@ -91,7 +91,8 @@ Java_com_google_android_filament_IndexBuffer_nSetBuffer(JNIEnv *env, jclass type
 
     auto* callback = JniBufferCallback::make(engine, env, handler, runnable, std::move(nioBuffer));
 
-    BufferDescriptor desc(data, sizeInBytes, &JniBufferCallback::invoke, callback);
+    BufferDescriptor desc(data, sizeInBytes,
+            callback->getHandler(), &JniBufferCallback::postToJavaAndDestroy, callback);
 
     indexBuffer->setBuffer(*engine, std::move(desc), (uint32_t) destOffsetInBytes);
 
diff --git a/android/filament-android/src/main/cpp/Renderer.cpp b/android/filament-android/src/main/cpp/Renderer.cpp
index f20b7a0bcf..fb9f5034f4 100644
--- a/android/filament-android/src/main/cpp/Renderer.cpp
+++ b/android/filament-android/src/main/cpp/Renderer.cpp
@@ -97,7 +97,8 @@ Java_com_google_android_filament_Renderer_nReadPixels(JNIEnv *env, jclass,
 
     PixelBufferDescriptor desc(buffer, sizeInBytes, (backend::PixelDataFormat) format,
             (backend::PixelDataType) type, (uint8_t) alignment, (uint32_t) left, (uint32_t) top,
-            (uint32_t) stride, &JniBufferCallback::invoke, callback);
+            (uint32_t) stride,
+            callback->getHandler(), &JniBufferCallback::postToJavaAndDestroy, callback);
 
     renderer->readPixels(uint32_t(xoffset), uint32_t(yoffset), uint32_t(width), uint32_t(height),
             std::move(desc));
@@ -132,7 +133,8 @@ Java_com_google_android_filament_Renderer_nReadPixelsEx(JNIEnv *env, jclass,
 
     PixelBufferDescriptor desc(buffer, sizeInBytes, (backend::PixelDataFormat) format,
             (backend::PixelDataType) type, (uint8_t) alignment, (uint32_t) left, (uint32_t) top,
-            (uint32_t) stride, &JniBufferCallback::invoke, callback);
+            (uint32_t) stride,
+            callback->getHandler(), &JniBufferCallback::postToJavaAndDestroy, callback);
 
     renderer->readPixels(renderTarget,
             uint32_t(xoffset), uint32_t(yoffset), uint32_t(width), uint32_t(height),
diff --git a/android/filament-android/src/main/cpp/Stream.cpp b/android/filament-android/src/main/cpp/Stream.cpp
index b7955f54d5..e84767d676 100644
--- a/android/filament-android/src/main/cpp/Stream.cpp
+++ b/android/filament-android/src/main/cpp/Stream.cpp
@@ -169,7 +169,8 @@ Java_com_google_android_filament_Stream_nReadPixels(JNIEnv *env, jclass,
 
     PixelBufferDescriptor desc(buffer, sizeInBytes, (backend::PixelDataFormat) format,
             (backend::PixelDataType) type, (uint8_t) alignment, (uint32_t) left, (uint32_t) top,
-            (uint32_t) stride, &JniBufferCallback::invoke, callback);
+            (uint32_t) stride,
+            callback->getHandler(), &JniBufferCallback::postToJavaAndDestroy, callback);
 
     stream->readPixels(uint32_t(xoffset), uint32_t(yoffset), uint32_t(width), uint32_t(height),
             std::move(desc));
@@ -221,5 +222,6 @@ Java_com_google_android_filament_Stream_nSetAcquiredImage(JNIEnv* env, jclass, j
 
 #endif
 
-    stream->setAcquiredImage((void*) nativeBuffer, &JniImageCallback::invoke, callback);
+    stream->setAcquiredImage((void*) nativeBuffer,
+            callback->getHandler(), &JniImageCallback::postToJavaAndDestroy, callback);
 }
diff --git a/android/filament-android/src/main/cpp/SwapChain.cpp b/android/filament-android/src/main/cpp/SwapChain.cpp
index 5528c00411..0ddc85f12f 100644
--- a/android/filament-android/src/main/cpp/SwapChain.cpp
+++ b/android/filament-android/src/main/cpp/SwapChain.cpp
@@ -27,5 +27,8 @@ Java_com_google_android_filament_SwapChain_nSetFrameCompletedCallback(JNIEnv* en
         jlong nativeSwapChain, jobject handler, jobject runnable) {
     SwapChain* swapChain = (SwapChain*) nativeSwapChain;
     auto *callback = JniCallback::make(env, handler, runnable);
-    swapChain->setFrameCompletedCallback(&JniCallback::invoke, callback);
+    swapChain->setFrameCompletedCallback([](void* user) {
+        JniCallback* callback = (JniCallback*)user;
+        JniCallback::postToJavaAndDestroy(callback);
+    }, callback);
 }
diff --git a/android/filament-android/src/main/cpp/Texture.cpp b/android/filament-android/src/main/cpp/Texture.cpp
index 5a63833da1..b4384eef56 100644
--- a/android/filament-android/src/main/cpp/Texture.cpp
+++ b/android/filament-android/src/main/cpp/Texture.cpp
@@ -210,7 +210,8 @@ Java_com_google_android_filament_Texture_nSetImage(JNIEnv* env, jclass, jlong na
 
     Texture::PixelBufferDescriptor desc(buffer, sizeInBytes, (backend::PixelDataFormat) format,
             (backend::PixelDataType) type, (uint8_t) alignment, (uint32_t) left, (uint32_t) top,
-            (uint32_t) stride, &JniBufferCallback::invoke, callback);
+            (uint32_t) stride,
+            callback->getHandler(), &JniBufferCallback::postToJavaAndDestroy, callback);
 
     texture->setImage(*engine, (size_t) level, (uint32_t) xoffset, (uint32_t) yoffset,
             (uint32_t) width, (uint32_t) height, std::move(desc));
@@ -240,7 +241,7 @@ Java_com_google_android_filament_Texture_nSetImageCompressed(JNIEnv *env, jclass
 
     Texture::PixelBufferDescriptor desc(buffer, sizeInBytes,
             (backend::CompressedPixelDataType) compressedFormat, (uint32_t) compressedSizeInBytes,
-            &JniBufferCallback::invoke, callback);
+            callback->getHandler(), &JniBufferCallback::postToJavaAndDestroy, callback);
 
     texture->setImage(*engine, (size_t) level, (uint32_t) xoffset, (uint32_t) yoffset,
             (uint32_t) width, (uint32_t) height, std::move(desc));
@@ -274,7 +275,8 @@ Java_com_google_android_filament_Texture_nSetImage3D(JNIEnv* env, jclass, jlong
 
     Texture::PixelBufferDescriptor desc(buffer, sizeInBytes, (backend::PixelDataFormat) format,
             (backend::PixelDataType) type, (uint8_t) alignment, (uint32_t) left, (uint32_t) top,
-            (uint32_t) stride, &JniBufferCallback::invoke, callback);
+            (uint32_t) stride,
+            callback->getHandler(), &JniBufferCallback::postToJavaAndDestroy, callback);
 
     texture->setImage(*engine, (size_t) level,
             (uint32_t) xoffset, (uint32_t) yoffset, (uint32_t) zoffset,
@@ -308,7 +310,7 @@ Java_com_google_android_filament_Texture_nSetImage3DCompressed(JNIEnv *env, jcla
 
     Texture::PixelBufferDescriptor desc(buffer, sizeInBytes,
             (backend::CompressedPixelDataType) compressedFormat, (uint32_t) compressedSizeInBytes,
-            &JniBufferCallback::invoke, callback);
+            callback->getHandler(), &JniBufferCallback::postToJavaAndDestroy, callback);
 
     texture->setImage(*engine, (size_t) level,
             (uint32_t) xoffset, (uint32_t) yoffset, (uint32_t) zoffset,
@@ -346,7 +348,8 @@ Java_com_google_android_filament_Texture_nSetImageCubemap(JNIEnv *env, jclass,
 
     Texture::PixelBufferDescriptor desc(buffer, sizeInBytes, (backend::PixelDataFormat) format,
             (backend::PixelDataType) type, (uint8_t) alignment, (uint32_t) left, (uint32_t) top,
-            (uint32_t) stride, &JniBufferCallback::invoke, callback);
+            (uint32_t) stride,
+            callback->getHandler(), &JniBufferCallback::postToJavaAndDestroy, callback);
 
     texture->setImage(*engine, (size_t) level, std::move(desc), faceOffsets);
 
@@ -381,7 +384,7 @@ Java_com_google_android_filament_Texture_nSetImageCubemapCompressed(JNIEnv *env,
 
     Texture::PixelBufferDescriptor desc(buffer, sizeInBytes,
             (backend::CompressedPixelDataType) compressedFormat, (uint32_t) compressedSizeInBytes,
-            &JniBufferCallback::invoke, callback);
+            callback->getHandler(), &JniBufferCallback::postToJavaAndDestroy, callback);
 
     texture->setImage(*engine, (size_t) level, std::move(desc), faceOffsets);
 
@@ -454,7 +457,7 @@ Java_com_google_android_filament_Texture_nGeneratePrefilterMipmap(JNIEnv *env, j
     Texture::PixelBufferDescriptor desc(buffer, sizeInBytes, (backend::PixelDataFormat) format,
             (backend::PixelDataType) type, (uint8_t) alignment,
             (uint32_t) left, (uint32_t) top, (uint32_t) stride,
-            &JniBufferCallback::invoke, callback);
+            callback->getHandler(), &JniBufferCallback::postToJavaAndDestroy, callback);
 
     Texture::PrefilterOptions options;
     options.sampleCount = sampleCount;
@@ -563,7 +566,7 @@ private:
     jobject mBitmap = nullptr;
     jobject mHandler = nullptr;
     jobject mCallback = nullptr;
-    AndroidBitmapInfo mInfo;
+    AndroidBitmapInfo mInfo{};
     CallbackJni mCallbackUtils;
 };
 
diff --git a/android/filament-android/src/main/cpp/VertexBuffer.cpp b/android/filament-android/src/main/cpp/VertexBuffer.cpp
index 8bc1e99e55..d5b3fc326d 100644
--- a/android/filament-android/src/main/cpp/VertexBuffer.cpp
+++ b/android/filament-android/src/main/cpp/VertexBuffer.cpp
@@ -32,40 +32,40 @@ using namespace filament::math;
 using namespace backend;
 
 extern "C" JNIEXPORT jlong JNICALL
-Java_com_google_android_filament_VertexBuffer_nCreateBuilder(JNIEnv *env, jclass type) {
+Java_com_google_android_filament_VertexBuffer_nCreateBuilder(JNIEnv*, jclass) {
     return (jlong) new VertexBuffer::Builder();
 }
 
 extern "C" JNIEXPORT void JNICALL
-Java_com_google_android_filament_VertexBuffer_nDestroyBuilder(JNIEnv *env, jclass type,
+Java_com_google_android_filament_VertexBuffer_nDestroyBuilder(JNIEnv*, jclass,
         jlong nativeBuilder) {
     VertexBuffer::Builder* builder = (VertexBuffer::Builder *) nativeBuilder;
     delete builder;
 }
 
 extern "C" JNIEXPORT void JNICALL
-Java_com_google_android_filament_VertexBuffer_nBuilderVertexCount(JNIEnv *env, jclass type,
+Java_com_google_android_filament_VertexBuffer_nBuilderVertexCount(JNIEnv*, jclass,
         jlong nativeBuilder, jint vertexCount) {
     VertexBuffer::Builder* builder = (VertexBuffer::Builder *) nativeBuilder;
     builder->vertexCount((uint32_t) vertexCount);
 }
 
 extern "C" JNIEXPORT void JNICALL
-Java_com_google_android_filament_VertexBuffer_nBuilderEnableBufferObjects(JNIEnv *env, jclass type,
+Java_com_google_android_filament_VertexBuffer_nBuilderEnableBufferObjects(JNIEnv*, jclass,
         jlong nativeBuilder, jboolean enabled) {
     VertexBuffer::Builder* builder = (VertexBuffer::Builder *) nativeBuilder;
     builder->enableBufferObjects(enabled);
 }
 
 extern "C" JNIEXPORT void JNICALL
-Java_com_google_android_filament_VertexBuffer_nBuilderBufferCount(JNIEnv *env, jclass type,
+Java_com_google_android_filament_VertexBuffer_nBuilderBufferCount(JNIEnv*, jclass,
         jlong nativeBuilder, jint bufferCount) {
     VertexBuffer::Builder* builder = (VertexBuffer::Builder *) nativeBuilder;
     builder->bufferCount((uint8_t) bufferCount);
 }
 
 extern "C" JNIEXPORT void JNICALL
-Java_com_google_android_filament_VertexBuffer_nBuilderAttribute(JNIEnv *env, jclass type,
+Java_com_google_android_filament_VertexBuffer_nBuilderAttribute(JNIEnv*, jclass,
         jlong nativeBuilder, jint attribute, jint bufferIndex, jint attributeType, jint byteOffset,
         jint byteStride) {
     VertexBuffer::Builder* builder = (VertexBuffer::Builder *) nativeBuilder;
@@ -75,14 +75,14 @@ Java_com_google_android_filament_VertexBuffer_nBuilderAttribute(JNIEnv *env, jcl
 }
 
 extern "C" JNIEXPORT void JNICALL
-Java_com_google_android_filament_VertexBuffer_nBuilderNormalized(JNIEnv *env, jclass type,
+Java_com_google_android_filament_VertexBuffer_nBuilderNormalized(JNIEnv*, jclass,
         jlong nativeBuilder, jint attribute, jboolean normalized) {
     VertexBuffer::Builder* builder = (VertexBuffer::Builder *) nativeBuilder;
     builder->normalized((VertexAttribute) attribute, normalized);
 }
 
 extern "C" JNIEXPORT jlong JNICALL
-Java_com_google_android_filament_VertexBuffer_nBuilderBuild(JNIEnv *env, jclass type,
+Java_com_google_android_filament_VertexBuffer_nBuilderBuild(JNIEnv*, jclass,
         jlong nativeBuilder, jlong nativeEngine) {
     VertexBuffer::Builder* builder = (VertexBuffer::Builder *) nativeBuilder;
     Engine *engine = (Engine *) nativeEngine;
@@ -90,14 +90,14 @@ Java_com_google_android_filament_VertexBuffer_nBuilderBuild(JNIEnv *env, jclass
 }
 
 extern "C" JNIEXPORT jint JNICALL
-Java_com_google_android_filament_VertexBuffer_nGetVertexCount(JNIEnv *env, jclass type,
+Java_com_google_android_filament_VertexBuffer_nGetVertexCount(JNIEnv*, jclass,
         jlong nativeVertexBuffer) {
     VertexBuffer *vertexBuffer = (VertexBuffer *) nativeVertexBuffer;
     return (jint) vertexBuffer->getVertexCount();
 }
 
 extern "C" JNIEXPORT jint JNICALL
-Java_com_google_android_filament_VertexBuffer_nSetBufferAt(JNIEnv *env, jclass type,
+Java_com_google_android_filament_VertexBuffer_nSetBufferAt(JNIEnv *env, jclass,
         jlong nativeVertexBuffer, jlong nativeEngine, jint bufferIndex,
         jobject buffer, jint remaining,
         jint destOffsetInBytes, jint count, jobject handler, jobject runnable) {
@@ -114,7 +114,8 @@ Java_com_google_android_filament_VertexBuffer_nSetBufferAt(JNIEnv *env, jclass t
 
     auto* callback = JniBufferCallback::make(engine, env, handler, runnable, std::move(nioBuffer));
 
-    BufferDescriptor desc(data, sizeInBytes, &JniBufferCallback::invoke, callback);
+    BufferDescriptor desc(data, sizeInBytes,
+            callback->getHandler(), &JniBufferCallback::postToJavaAndDestroy, callback);
 
     vertexBuffer->setBufferAt(*engine, (uint8_t) bufferIndex, std::move(desc),
             (uint32_t) destOffsetInBytes);
@@ -123,7 +124,7 @@ Java_com_google_android_filament_VertexBuffer_nSetBufferAt(JNIEnv *env, jclass t
 }
 
 extern "C" JNIEXPORT void JNICALL
-Java_com_google_android_filament_VertexBuffer_nSetBufferObjectAt(JNIEnv *env, jclass type,
+Java_com_google_android_filament_VertexBuffer_nSetBufferObjectAt(JNIEnv*, jclass,
         jlong nativeVertexBuffer, jlong nativeEngine, jint bufferIndex, jlong nativeBufferObject) {
     VertexBuffer *vertexBuffer = (VertexBuffer *) nativeVertexBuffer;
     Engine *engine = (Engine *) nativeEngine;
diff --git a/android/filament-android/src/main/cpp/View.cpp b/android/filament-android/src/main/cpp/View.cpp
index 5361c56fe7..686867f5eb 100644
--- a/android/filament-android/src/main/cpp/View.cpp
+++ b/android/filament-android/src/main/cpp/View.cpp
@@ -22,6 +22,8 @@
 
 #include "common/CallbackUtils.h"
 
+#include "private/backend/VirtualMachineEnv.h"
+
 using namespace filament;
 
 extern "C" JNIEXPORT void JNICALL
@@ -387,7 +389,7 @@ Java_com_google_android_filament_View_nIsScreenSpaceRefractionEnabled(JNIEnv *,
 
 extern "C"
 JNIEXPORT void JNICALL
-Java_com_google_android_filament_View_nPick(JNIEnv* env, jclass clazz,
+Java_com_google_android_filament_View_nPick(JNIEnv* env, jclass,
         jlong nativeView,
         jint x, jint y, jobject handler, jobject internalCallback) {
 
@@ -412,13 +414,14 @@ Java_com_google_android_filament_View_nPick(JNIEnv* env, jclass clazz,
     View* view = (View*) nativeView;
     JniCallback *callback = JniCallback::make(env, handler, internalCallback);
     view->pick(x, y, [callback](View::PickingQueryResult const& result) {
+        // this is executed on the backend/service thread
         jobject obj = callback->getCallbackObject();
-        JNIEnv* const env = callback->getJniEnv();
+        JNIEnv* env = filament::VirtualMachineEnv::get().getEnvironment();
         env->SetIntField(obj, jniState.renderableFieldId, (jint)result.renderable.getId());
         env->SetFloatField(obj, jniState.depthFieldId, result.depth);
         env->SetFloatField(obj, jniState.fragCoordXFieldId, result.fragCoords.x);
         env->SetFloatField(obj, jniState.fragCoordYFieldId, result.fragCoords.y);
         env->SetFloatField(obj, jniState.fragCoordZFieldId, result.fragCoords.z);
-        JniCallback::invoke(callback);  // this destroys JniCallback
-    });
+        JniCallback::postToJavaAndDestroy(callback);
+    }, callback->getHandler());
 }
diff --git a/android/filament-utils-android/CMakeLists.txt b/android/filament-utils-android/CMakeLists.txt
index 267e1aa29c..c5c214e216 100644
--- a/android/filament-utils-android/CMakeLists.txt
+++ b/android/filament-utils-android/CMakeLists.txt
@@ -50,6 +50,7 @@ target_compile_definitions(filament-utils-jni PUBLIC IMAGEIO_LITE=1)
 target_include_directories(filament-utils-jni PRIVATE
         ${FILAMENT_DIR}/include
         ..
+        ../../filament/backend/include
         ${IMAGEIO_DIR}/include
         ../../libs/utils/include)
 
diff --git a/android/gltfio-android/CMakeLists.txt b/android/gltfio-android/CMakeLists.txt
index d52989cac3..916ff0226a 100644
--- a/android/gltfio-android/CMakeLists.txt
+++ b/android/gltfio-android/CMakeLists.txt
@@ -76,6 +76,7 @@ set(GLTFIO_INCLUDE_DIRS
         ..
         ${FILAMENT_DIR}/include
         ${FILAMENT_DIR}/include/gltfio/resources
+        ../../filament/backend/include
         ../../libs/gltfio/include
         ../../third_party/cgltf
         ../../third_party/robin-map
diff --git a/filament/backend/CMakeLists.txt b/filament/backend/CMakeLists.txt
index a8defa495d..ba9070805c 100644
--- a/filament/backend/CMakeLists.txt
+++ b/filament/backend/CMakeLists.txt
@@ -81,10 +81,14 @@ if (FILAMENT_SUPPORTS_OPENGL AND NOT FILAMENT_USE_EXTERNAL_GLES3 AND NOT FILAMEN
     if (EGL)
         list(APPEND SRCS src/opengl/PlatformEGL.cpp)
     endif()
+    if (ANDROID)
+        # FIXME: this should be included when we build for JAVA (which is implied by ANDROID)
+        #        but is not specific to ANDROID
+        list(APPEND SRCS src/VirtualMachineEnv.cpp)
+    endif ()
     if (ANDROID)
         list(APPEND SRCS src/android/ExternalStreamManagerAndroid.cpp)
         list(APPEND SRCS src/android/ExternalTextureManagerAndroid.cpp)
-        list(APPEND SRCS src/android/VirtualMachineEnv.cpp)
         list(APPEND SRCS src/opengl/PlatformEGLAndroid.cpp)
     elseif (IOS)
         list(APPEND SRCS src/opengl/PlatformCocoaTouchGL.mm)
diff --git a/filament/backend/include/backend/CallbackHandler.h b/filament/backend/include/backend/CallbackHandler.h
index e2ce6a6ea1..dee3aaa251 100644
--- a/filament/backend/include/backend/CallbackHandler.h
+++ b/filament/backend/include/backend/CallbackHandler.h
@@ -36,6 +36,22 @@ namespace filament::backend {
  *
  * CallbackHandler* can always be nullptr in which case the default handler is used. The
  * default handler always dispatches callbacks on filament's main thread opportunistically.
+ *
+ * Life time:
+ * ---------
+ *
+ * Filament make no attempts to manage the life time of the CallbackHandler* and never takes
+ * ownership.
+ * In particular, this means that the CallbackHandler instance must stay valid until all
+ * pending callbacks are been dispatched.
+ *
+ * Similarly, when shutting down filament, care must be taken to ensure that all pending callbacks
+ * that might access filament's state have been dispatched. Filament can no longer ensure this
+ * because callback execution is the responsibility of the CallbackHandler, which is external to
+ * filament.
+ * Typically, the concrete CallbackHandler would have a mechanism to drain and/or wait for all
+ * callbacks to be processed.
+ *
  */
 class CallbackHandler {
 public:
@@ -44,6 +60,8 @@ public:
     /**
      * Schedules the callback to be called onto the appropriate thread.
      * Typically this will be the application's main thead.
+     *
+     * Must be thread-safe.
      */
     virtual void post(void* user, Callback callback) = 0;
 
diff --git a/filament/backend/src/android/VirtualMachineEnv.h b/filament/backend/include/private/backend/VirtualMachineEnv.h
similarity index 100%
rename from filament/backend/src/android/VirtualMachineEnv.h
rename to filament/backend/include/private/backend/VirtualMachineEnv.h
diff --git a/filament/backend/src/android/VirtualMachineEnv.cpp b/filament/backend/src/VirtualMachineEnv.cpp
similarity index 97%
rename from filament/backend/src/android/VirtualMachineEnv.cpp
rename to filament/backend/src/VirtualMachineEnv.cpp
index 1122e69d61..9ea660dea7 100644
--- a/filament/backend/src/android/VirtualMachineEnv.cpp
+++ b/filament/backend/src/VirtualMachineEnv.cpp
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-#include "VirtualMachineEnv.h"
+#include "private/backend/VirtualMachineEnv.h"
 
 #include <utils/debug.h>
 
diff --git a/filament/backend/src/android/ExternalStreamManagerAndroid.h b/filament/backend/src/android/ExternalStreamManagerAndroid.h
index 323fc8f9be..addf4b7a0f 100644
--- a/filament/backend/src/android/ExternalStreamManagerAndroid.h
+++ b/filament/backend/src/android/ExternalStreamManagerAndroid.h
@@ -17,7 +17,7 @@
 #ifndef TNT_FILAMENT_DRIVER_ANDROID_EXTERNAL_STREAM_MANAGER_ANDROID_H
 #define TNT_FILAMENT_DRIVER_ANDROID_EXTERNAL_STREAM_MANAGER_ANDROID_H
 
-#include "android/VirtualMachineEnv.h"
+#include "private/backend/VirtualMachineEnv.h"
 
 #include <backend/Platform.h>
 
diff --git a/filament/backend/src/android/ExternalTextureManagerAndroid.h b/filament/backend/src/android/ExternalTextureManagerAndroid.h
index 9b7efc4dbb..faa04b9efb 100644
--- a/filament/backend/src/android/ExternalTextureManagerAndroid.h
+++ b/filament/backend/src/android/ExternalTextureManagerAndroid.h
@@ -17,7 +17,7 @@
 #ifndef TNT_FILAMENT_DRIVER_ANDROID_EXTERNAL_TEXTURE_MANAGER_ANDROID_H
 #define TNT_FILAMENT_DRIVER_ANDROID_EXTERNAL_TEXTURE_MANAGER_ANDROID_H
 
-#include "android/VirtualMachineEnv.h"
+#include "private/backend/VirtualMachineEnv.h"
 
 #include <backend/DriverEnums.h>
 #include <backend/Platform.h>
diff --git a/filament/backend/src/opengl/PlatformEGLAndroid.cpp b/filament/backend/src/opengl/PlatformEGLAndroid.cpp
index 2d0a5ca80b..28ba47a477 100644
--- a/filament/backend/src/opengl/PlatformEGLAndroid.cpp
+++ b/filament/backend/src/opengl/PlatformEGLAndroid.cpp
@@ -21,7 +21,7 @@
 
 #include "android/ExternalTextureManagerAndroid.h"
 #include "android/ExternalStreamManagerAndroid.h"
-#include "android/VirtualMachineEnv.h"
+#include "private/backend/VirtualMachineEnv.h"
 
 #include <android/api-level.h>
 
@@ -236,7 +236,7 @@ AcquiredImage PlatformEGLAndroid::transformAcquiredImage(AcquiredImage source) n
     return { eglImage, patchedCallback, closure, source.handler };
 }
 
-// This must called when the library is loaded. We need this to get a reference to the global VM
+// This must be called when the library is loaded. We need this to get a reference to the global VM
 void JNI_OnLoad(JavaVM* vm, void* reserved) {
     ::filament::VirtualMachineEnv::JNI_OnLoad(vm);
 }