android - 在android studio项目中链接.so库

Question

如标题所示，我正在尝试将原生 .so 链接到 android studio 项目。我浏览了 android 开发者网站上的文档和更多文章，但未能将 .so 文件与项目连接起来。

每当我尝试运行代码时，我都会收到以下错误

CMake Error: The following variables are used in this project, but they are set to NOTFOUND. Please set them or make sure they are set and tested correctly in the CMake files: testlib

这是我的CMake文件

cmake_minimum_required(VERSION 3.4.1)

add_library( # Sets the name of the library.
             native-lib

             # Sets the library as a shared library.
             SHARED

             # Provides a relative path to your source file(s).
             src/main/cpp/native-lib.cpp )

find_library( # Sets the name of the path variable.
              log-lib

              # Specifies the name of the NDK library that
              # you want CMake to locate.
              log )

add_library(testlib SHARED IMPORTED)

set_property(TARGET testlib PROPERTY IMPORTED_LOCATION "E:/project/Remote_Native/remote_attempt_1/app/libs/armeabi-v7a/libremotedesktop_client.so")

#find_path(testlib E:/project/Remote_Native/remote_attempt_1/app/libs/armeabi-v7a/RemoteDesktop.h)
find_library(testlib E:/project/Remote_Native/remote_attempt_1/app/libs/armeabi-v7a/libremotedesktop_client.so)

#add_library(remote SHARED IMPORTED)

#set_target_properties(remote PROPERTIES IMPORTED_LOCATION libs/${ANDROID_ABI}/libremotedesktop_client.so )

# Specifies libraries CMake should link to your target library. You
# can link multiple libraries, such as libraries you define in this
# build script, prebuilt third-party libraries, or system libraries.

target_link_libraries( # Specifies the target library.
                       native-lib

                       # Links the target library to the log library
                       # included in the NDK.
                       ${log-lib}

                       ${testlib})

target_include_directories()

我有四个 .so 文件，每个文件用于 arm64、armeabi、armeabi-v7a、x86。我在路径中对 armeabi-v7a lib 进行了硬编码，当我这样做时，android studio 抛出了上述错误。我的实际目标是根据手机中的芯片动态加载库。我很确定我当前的代码没有实现这一目标。

这是我的问题

1. 如何解决我遇到的错误？我已尝试同时提供相对路径和绝对路径，但无济于事，我遇到了同样的错误。

2. 如何将 .so 和 .h 文件添加到原生 android studio 项目中？那有基于运行代码的芯片的变化吗？

3. 当我直接将 .h 文件添加到 native 文件夹时，我可以在我的 C 代码中引用该 header 中的类和函数，但我无法运行该代码。我在 .h 文件中有一个 getInstance() 方法。每当我调用getInstance() 函数表示 undefined reference to getInstance()。据我了解，“.h”文件已正确链接，但 .so 文件中实际存在的 .h 文件的功能定义是没有联系。我相信如果问题 1 和 2 得到回答，这个问题就会得到解决。

4. 是不是所有的原生android项目都需要一个.mk文件？我没有将它添加到我的项目中，我认为这可能是我遇到错误的原因之一。

Answer 1

在您的情况下，您不需要 find_library。对于log，库是NDK帮你解析的；对于 libremotedesktop_client.so，您知道确切的路径。

这是适合您的 CMakeLists.txt:

cmake_minimum_required(VERSION 3.4.1)

add_library( # Sets the name of the library.
             native-lib

             # Sets the library as a shared library.
             SHARED

             # Provides a relative path to your source file(s).
             src/main/cpp/native-lib.cpp )

add_library(remote SHARED IMPORTED)

set_property(TARGET remote PROPERTY IMPORTED_LOCATION "E:/project/Remote_Native/remote_attempt_1/app/libs/${ANDROID_ABI}/libremotedesktop_client.so")

# Specifies libraries CMake should link to your target library. You
# can link multiple libraries, such as libraries you define in this
# build script, prebuilt third-party libraries, or system libraries.

target_link_libraries( # Specifies the target library.
                       native-lib

                       # Links the target library to the log library
                       # included in the NDK.
                       log

                       remote)

请注意，在 CMake 脚本中使用完整路径 (E:/project...) 并不是最佳做法；您可能可以相对于 CMakeLists.txt 的路径以某种方式表达该库的路径，即 ${CMAKE_CURRENT_SOURCE_DIR}。