使用 android ndk 编译 dlib 和 opencv

Question

我是一名 android 开发人员，但我是 Android NDK 的新手，请帮忙，或者告诉我您还需要什么/您将如何尝试解决此类问题。

我将this dlib 用于android 示例和官方opencv for android library，我想将两者集成到一个应用程序中。当我尝试构建项目时，出现以下错误：

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':openCVSamplefacedetection:externalNativeBuildDebug'.
> Build command failed.
  Error while executing process /home/feli/Android/Sdk/ndk-bundle/ndk-build with arguments {NDK_PROJECT_PATH=null APP_BUILD_SCRIPT=/home/feli/Development/android/test/face-detection/openCVSamplefacedetection/src/main/jni/Android.mk NDK_APPLICATION_MK=/home/feli/Development/android/test/face-detection/openCVSamplefacedetection/src/main/jni/Application.mk APP_ABI=mips64 NDK_ALL_ABIS=mips64 NDK_DEBUG=1 APP_PLATFORM=android-21 NDK_OUT=/home/feli/Development/android/test/face-detection/openCVSamplefacedetection/build/intermediates/ndkBuild/debug/obj NDK_LIBS_OUT=/home/feli/Development/android/test/face-detection/openCVSamplefacedetection/build/intermediates/ndkBuild/debug/lib /home/feli/Development/android/test/face-detection/openCVSamplefacedetection/build/intermediates/ndkBuild/debug/obj/local/mips64/libdetection_based_tracker.so}
  [mips64] Compile++      : detection_based_tracker <= DetectionBasedTracker_jni.cpp
  [mips64] Prebuilt       : libopencv_java3.so <= /home/feli/Android/openCV/OpenCV-android-sdk/sdk/native/jni/../libs/mips64/
  [mips64] SharedLibrary  : libdetection_based_tracker.so
  /home/feli/Development/android/test/face-detection/openCVSamplefacedetection/build/intermediates/ndkBuild/debug/obj/local/mips64/objs-debug/detection_based_tracker/DetectionBasedTracker_jni.o: In function `dlib_check_consistent_assert_usage':
  /home/feli/Development/android/test/face-detection/openCVSamplefacedetection/src/main/jni/dlib/dlib/threads/threads_kernel_shared.h:44: undefined reference to `USER_ERROR__missing_dlib_all_source_cpp_file__OR__inconsistent_use_of_DEBUG_or_ENABLE_ASSERTS_preprocessor_directives_'
  clang++: error: linker command failed with exit code 1 (use -v to see invocation)
  make: *** [/home/feli/Development/android/test/face-detection/openCVSamplefacedetection/build/intermediates/ndkBuild/debug/obj/local/mips64/libdetection_based_tracker.so] Error 1


* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output.

我的第一个猜测是我没有将 source.cpp 包含在我的 Android.mk 中，但是将其放置到 src 文件中并没有解决问题。 这是我的 Android.mk：

LOCAL_PATH := $(call my-dir)

## Build dlib to static library
include $(CLEAR_VARS)
LOCAL_MODULE := dlib
LOCAL_C_INCLUDES := $(LOCAL_PATH)/dlib

LOCAL_SRC_FILES += \
                $(LOCAL_PATH)/dlib/dlib/all/source.cpp \
                $(LOCAL_PATH)/dlib//dlib/threads/threads_kernel_shared.cpp \
                $(LOCAL_PATH)/dlib/dlib/entropy_decoder/entropy_decoder_kernel_2.cpp \
                $(LOCAL_PATH)/dlib/dlib/base64/base64_kernel_1.cpp \
                $(LOCAL_PATH)/dlib/dlib/threads/threads_kernel_1.cpp \
                $(LOCAL_PATH)/dlib/dlib/threads/threads_kernel_2.cpp

LOCAL_EXPORT_C_INCLUDES := $(LOCAL_C_INCLUDES)
include $(BUILD_STATIC_LIBRARY)

# Build opencv
include $(CLEAR_VARS)
OPENCVROOT := ~/Android/openCV/OpenCV-android-sdk
OPENCV_CAMERA_MODULES:=on
OPENCV_INSTALL_MODULES:=on
OPENCV_LIB_TYPE := SHARED
include ${OPENCVROOT}/sdk/native/jni/OpenCV.mk

LOCAL_MODULE     := detection_based_tracker
LOCAL_C_INCLUDES += $(LOCAL_PATH)
LOCAL_SRC_FILES  := DetectionBasedTracker_jni.cpp

LOCAL_LDLIBS     += -lm -llog -ldl -lz -ljnigraphics
LOCAL_CPPFLAGS += -fexceptions -frtti -std=c++11

# LOCAL_STATIC_LIBRARIES += dlib

include $(BUILD_SHARED_LIBRARY)

也许NDK_PROJECT_PATH=null 是问题所在？比为什么这两个图书馆分开建设？或者还有什么问题？我尝试了很多修改 Android.mk，但它的工作对我来说是个谜。 任何帮助或意见都会很有用。

编辑：

当我注释掉LOCAL_STATIC_LIBRARIES += dlib 行时，出现以下异常：

Build command failed.
  Error while executing process /home/feli/Android/Sdk/ndk-bundle/ndk-build with arguments {NDK_PROJECT_PATH=null APP_BUILD_SCRIPT=/home/feli/Development/android/test/face-detection/openCVSamplefacedetection/src/main/jni/Android.mk NDK_APPLICATION_MK=/home/feli/Development/android/test/face-detection/openCVSamplefacedetection/src/main/jni/Application.mk APP_ABI=mips64 NDK_ALL_ABIS=mips64 NDK_DEBUG=1 APP_PLATFORM=android-21 NDK_OUT=/home/feli/Development/android/test/face-detection/openCVSamplefacedetection/build/intermediates/ndkBuild/debug/obj NDK_LIBS_OUT=/home/feli/Development/android/test/face-detection/openCVSamplefacedetection/build/intermediates/ndkBuild/debug/lib /home/feli/Development/android/test/face-detection/openCVSamplefacedetection/build/intermediates/ndkBuild/debug/obj/local/mips64/libdetection_based_tracker.so}
  [mips64] Compile++      : detection_based_tracker <= DetectionBasedTracker_jni.cpp
  [mips64] Compile++      : dlib <= source.cpp
  In file included from /home/feli/Development/android/test/face-detection/openCVSamplefacedetection/src/main/jni/dlib/dlib/all/source.cpp:76:
  In file included from /home/feli/Development/android/test/face-detection/openCVSamplefacedetection/src/main/jni/dlib/dlib/all/../gui_widgets/fonts.cpp:14:
  /home/feli/Development/android/test/face-detection/openCVSamplefacedetection/src/main/jni/dlib/dlib/all/../gui_widgets/nativefont.h:27:10: fatal error: 'X11/Xlib.h' file not found
  #include <X11/Xlib.h>
           ^~~~~~~~~~~~
  1 error generated.
  make: *** [/home/feli/Development/android/test/face-detection/openCVSamplefacedetection/build/intermediates/ndkBuild/debug/obj/local/mips64/objs-debug/dlib//home/feli/Development/android/test/face-detection/openCVSamplefacedetection/src/main/jni/dlib/dlib/all/source.o] Error 1

Answer 1

dlib 使用 cmake，这不是一个简单的设置。经验丰富的专业人员可能需要很长时间才能为此库准备 ndk-build 脚本。

我建议您使用 cmake 构建您的原生库，而不是 ndk-build。您可以找到使用 OpenCv on GitHub 的本机库示例。

另外，我建议您从将 abiFilters 设置为仅一个最相关的 ABI 开始，并且只有当您看到一切都适合您时，您才能为其他 ABI 构建您的项目。请记住，对于某些库来说，移植到所有 ABI 可能会很棘手。而且，如果您没有一个平台来至少对某些 ABI 执行简短的健全性检查，那么构建它是没有意义的。