无法使find_package( opencv )在opencv 3.3rc上用于android：

Question

我正在尝试集成新的Opencv3.3rc标记，以使用OpenCV dnn模块。https://github.com/opencv/opencv/tree/3.3.0-rc

我可以交叉编译OpenCV库，但是当我试图使FindOpencv必需时，我有以下错误：

在已经定义的导出集中，有些(但不是全部)目标。

注册的唯一目标是cpufeatures，如您所见：

  Targets Defined: cpufeatures
  Targets not yet defined:
  libtiff;libjpeg;libwebp;libjasper;libpng;IlmImf;tegra_hal;libprotobuf;opencv_core;opencv_flann;opencv_imgproc;opencv_ml;opencv_objdetect;opencv_photo;opencv_video;opencv_dnn;opencv_imgcodecs;opencv_shape;opencv_videoio;opencv_highgui;opencv_superres;opencv_features2d;opencv_calib3d;opencv_java;opencv_stitching;opencv_videostab

正如我在OpenCVconfig.cmake配置文件中所看到的，目前有两种方法可以找到OpenCV：

这是：

find_package(OpenCV REQUIRED)

或定义模块：

find_package(OpenCV REQUIRED core videoio)

但它们都不起作用。

错误来自于这个代码片段OpenCVModules.cmake。

# Commands may need to know the format version.
set(CMAKE_IMPORT_FILE_VERSION 1)

# Protect against multiple inclusion, which would fail when already imported targets are added once more.
set(_targetsDefined)
set(_targetsNotDefined)
set(_expectedTargets)
foreach(_expectedTarget cpufeatures libtiff libjpeg libwebp libjasper libpng IlmImf tegra_hal libprotobuf opencv_core opencv_flann opencv_imgproc opencv_ml opencv_objdetect opencv_photo opencv_video opencv_dnn opencv_imgcodecs opencv_shape opencv_videoio opencv_highgui opencv_superres opencv_features2d opencv_calib3d opencv_java opencv_stitching opencv_videostab)
  list(APPEND _expectedTargets ${_expectedTarget})
  if(NOT TARGET ${_expectedTarget})
    list(APPEND _targetsNotDefined ${_expectedTarget})
  endif()
  if(TARGET ${_expectedTarget})
    list(APPEND _targetsDefined ${_expectedTarget})
  endif()
endforeach()
if("${_targetsDefined}" STREQUAL "${_expectedTargets}")
  unset(_targetsDefined)
  unset(_targetsNotDefined)
  unset(_expectedTargets)
  set(CMAKE_IMPORT_FILE_VERSION)
  cmake_policy(POP)
  return()
endif()
if(NOT "${_targetsDefined}" STREQUAL "")
  message(FATAL_ERROR "Some (but not all) targets in this export set were already defined.\nTargets Defined: ${_targetsDefined}\nTargets not yet defined: ${_targetsNotDefined}\n")
endif()

有人知道怎么会发生这种事吗？

Answer 1

我找到了答案：

我之前定义了cpu特性库，所以这段代码是CMakelists.txt中冲突的部分。

add_library(cpufeatures STATIC
            ${ANDROID_NDK}/sources/android/cpufeatures/cpu-features.c)

除去这一部分，问题就解决了。