如何在android Studio中创建一个C++类（.h和.cpp）？

Question

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出错原因：任务“：app：ExternalNativeBuildDebug”执行失败。

生成命令失败。执行带有参数的'C:\users\lucien.moor\appdata\local\android\sdk\cmake\3.6.3155560\bin\cmake.exe'时出错{--build C:\users\lucien.moor\deskt\tmp\myapplication2\app.externalnativeBuild\cmak\debug\tmp\myapplication2\externalnativeBuild\cmak\mipg\mipg\mips64-target native-lib}[1/2]构建CXX对象cmakefiles cien.moor\appdata\local\android\sdk\ndk-bundle\toolchains\llvm\prebuild\windows-x86_64\bin\clang++.exe--target=mips64el-none-linux-android--gcc-toolchain=c://users/lucien.moor/appdata/local/android/sdk/ndk-bundle/doolchains/mips64el-linux-android-4.9/prebuilt/windows-x86_64-sysroot=21/arch-mips64-fpic-g-dandroid-ffunction-sections-funwind-tables-fstack-protector-strong-no-canonical-prefixes-wa,--noexecstack-wformat-werror=format-security-g-dandroid-ffunction-sections-funwind-tables-fstack-protector-strong-no-canonical-prefixes-wa,--noexecstack-wformat-werror=format-security-o0-fno-limit-debug-info-o0-fno-limit-debug-info-o0-fno-limit-debug-info-wl,--build-id-wl,--warn-shared-textel-wl,--fatal-warning-wl,-undefined-wl,-z,noexecstack-qunused-arguments-wl,-z,relro-wl,-z,now-shared-wl,-soname,libnative-lib.so-o..............\build\meditiates\cmake\debug\obj\mips64\libnative-lib.so cmakefiles/native-lib.dir/src/main/cpp/native-lib.cpp.o-llog-lm“c：.”cmakefiles/native-lib.dir/src/main/cpp/native-lib.cpp.o:In functionjava_he_1arc_myapplication2_mainactivity_stringfromjni':c:\users\lucien.moor\desktop\tmp\myapplication2\app\src\main\cpp/native-lib.cpp:10:helloworld::helloworld()'clang++.exe:错误：链接器命令失败，退出代码为1（使用-v查看调用）忍者：构建停止：子命令失败。

try：使用--stacktrace选项运行以获取堆栈跟踪。使用--info或--debug选项运行以获得更多日志输出。

我认为在链接.h和.cpp文件时有问题。当我尝试内联实现我的构造函数时，它工作得很好。它只是找不到。cpp实现。

以下是我的JNI native-lib.cpp文件：

#include <jni.h>
#include <string>
#include "HelloWorld.h"

extern "C"
jstring
Java_he_1arc_myapplication2_MainActivity_stringFromJNI(
JNIEnv *env,
jobject /* this */) {
HelloWorld t;
std::string hello = "Hello from C++";
return env->NewStringUTF(hello.c_str());
}

#ifndef MYAPPLICATION2_HELLOWORLD_H
#define MYAPPLICATION2_HELLOWORLD_H


class HelloWorld {
public:
     HelloWorld();
};
#endif //MYAPPLICATION2_HELLOWORLD_H

#include "HelloWorld.h"
HelloWorld::HelloWorld() { }

Answer 1

我找到解决办法了！

正如消息所建议的，我必须在cmakelists.txt中添加我的文件。Headers文件不是必需的，但是必须在cmakelists.txt中添加。cpp文件

为了允许链接器查找实现文件，我必须添加

src/main/cpp/HelloWorld.cpp in my 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).
         # Associated headers in the same location as their source
         # file are automatically included.
         src/main/cpp/native-lib.cpp
         src/main/cpp/HelloWorld.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 )
target_link_libraries( # Specifies the target library.
                   native-lib
                   # Links the target library to the log library
                   # included in the NDK.
                   ${log-lib} )