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android - 无法将标准库导入本机 android 项目中的头文件

问题描述

我正在尝试将 PC C++ 项目编译为 android。我编译了模板示例，它在我的设备上也能正常工作。

一开始，我只创建了一个简单的头文件，但是我无法导入简单的标准库，例如： #include <string>

奇怪的是，如果我将其更改为cpp文件，则所有内容都可以正常导入。

这就是我所做的：

CMakeList.txt

# For more information about using CMake with Android Studio, read the
# documentation: https://d.android.com/studio/projects/add-native-code.html

# Sets the minimum version of CMake required to build the native library.

cmake_minimum_required(VERSION 3.4.1)

set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11 -Werror")
# Creates and names a library, sets it as either STATIC
# or SHARED, and provides the relative paths to its source code.
# You can define multiple libraries, and CMake builds them for you.
# Gradle automatically packages shared libraries with your APK.

# now build app's shared lib

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).
        native-lib.cpp
        BoolPair.h
        )

# Searches for a specified prebuilt library and stores the path as a
# variable. Because CMake includes system libraries in the search path by
# default, you only need to specify the name of the public NDK library
# you want to add. CMake verifies that the library exists before
# completing its build.

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)

# 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})

应用程序构建.gradle

android {
    ...
    defaultConfig {
        ...
        externalNativeBuild {
            cmake {
                arguments "-DANDROID_STL=c++_shared"
                cppFlags += "-std=c++11"

            }
        }
    }

标签： androidc++cmakeandroid-ndk

解决方案

您尚未在 CMake 文件中指定要支持的语言。project()常见的 CMake 习惯用法是在文件顶部指定调用，可以选择指定目标语言：

cmake_minimum_required(VERSION 3.4.1)
project(MyProjectName CXX)

未指定语言时，CMake 默认启用 C 和 C++ 语言。

目前尚不清楚您如何能够仅将一个.h文件添加到您的目标native-lib。这通常会导致 CMake 错误：

CMake can not determine linker language for target

无论如何，在您的情况下，CMake 似乎选择了 C 编译器，因为没有明确指定语言。#include <string>不支持使用 C 编译器。

另一方面，通过在.cpp文件头中包含一个文件，CMake 现在根据文件扩展名确定这是 C++ 源代码。在这种情况下，使用并<string>接受了 C++ 编译器。

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