Resolve native libraries from AAR file (Maven)

README.md

@@ -19,7 +19,6 @@ Copyright of the logo: The Coca-Cola Company
 ### How do I get set up?
 * IDE: Android Studio (tested with 2023.3.1)
 * Android SDK & NDK
-* Dependencies: OpenCV 4 library (included) [License](/opencv/LICENSE) [Copyright](/opencv/COPYRIGHT)
 * Template image location: res/drawable Changeable in CameraPreviewView
 
 ### Default template image

app/CMakeLists.txt

@@ -1,57 +1,27 @@
-
-#
-# Copyright (C) The Android Open Source Project
-#
-# Licensed under the Apache License, Version 2.0 (the "License");
-# you may not use this file except in compliance with the License.
-# You may obtain a copy of the License at
-#
-#      http://www.apache.org/licenses/LICENSE-2.0
-#
-# Unless required by applicable law or agreed to in writing, software
-# distributed under the License is distributed on an "AS IS" BASIS,
-# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-# See the License for the specific language governing permissions and
-# limitations under the License.
-#
-
 cmake_minimum_required(VERSION 3.4.1)
 
-project(FeatureMatchingNative)
+# register the project for the C++ language
+project(app CXX)
 
-# create a variable for accessing the opencv library dir
-set(
-        lib_src_dir
-        ${CMAKE_SOURCE_DIR}/../opencv/native
-)
+# find the opencv native sdk inside the AAR file / maven dependency (prerequisite: prefab = true)
+find_package(OpenCV REQUIRED CONFIG)
 
-# register the opencv header files...
-include_directories(${lib_src_dir}/jni/include)
-
-# register a new library to import...
+# register the custom c++ code of the app
 add_library(
-        lib_opencv
+        app
         SHARED
-        IMPORTED
+        src/main/cpp/native_opencv.cpp
 )
-# ...and assign the corresponding location of the precompiled opencv library
+# compile with c++20
 set_target_properties(
-        lib_opencv
-        PROPERTIES IMPORTED_LOCATION
-        ${lib_src_dir}/libs/${ANDROID_ABI}/libopencv_java4.so
-)
-
-# register the custom c++ code of the app as library
-add_library(
-        native_opencv
-        SHARED
-        src/main/cpp/native_opencv.cpp
+        app
+        PROPERTIES
+        CXX_STANDARD 20
 )
 
 # link the required libs together
 target_link_libraries(
-        native_opencv # includes the custom c++ code of the app
-        lib_opencv # includes the precompiled opencv lib
-        android # include android sdk
+        app # includes the custom c++ code of the app
+        OpenCV::opencv_java4 # includes the opencv lib from the maven dependency
         log # include android logging sdk
 )

app/build.gradle

@@ -22,9 +22,10 @@ android {
         }
         externalNativeBuild {
             cmake {
-                cppFlags += "-std=c++20"
+                arguments "-DANDROID_STL=c++_shared"
             }
         }
+
     }
     buildTypes {
         release {
@@ -38,6 +39,9 @@ android {
             path 'CMakeLists.txt'
         }
     }
+    buildFeatures {
+        prefab true // allows to access native libraries from OpenCV AAR in C++
+    }
 }
 
 kotlin.jvmToolchain(java_version)

app/src/main/java/com/michaeltroger/featureMatchingNative/views/CameraPreviewView.kt

@@ -255,7 +255,7 @@ class CameraPreviewView(
 
         // loading C++ libraries
         init {
-            System.loadLibrary("native_opencv")
+            System.loadLibrary("app")
         }
     }