Android NDK使用.so库从JNI里面的c代码 [英] Android NDK use .so library from c code inside JNI

问题描述

我在SO上发现了类似的问题，但都没有使用相同的工作流程。

I found similar questions on SO but none of them were with the same workflow.

我在我的项目中有一个.so库（libcurl）。

I have a .so library (libcurl) in my project. The project builds but I need to get a hold of curl.h in my c code inside JNI.

这是我的Android.mk文件：

Here's my Android.mk file:

LOCAL_PATH:= $(call my-dir)

LIBS_PATH := libs/$(TARGET_ARCH_ABI)

include $(CLEAR_VARS)
LOCAL_MODULE := libcurl                     
LOCAL_SRC_FILES := $(LIBS_PATH)/libcurl.so
include $(PREBUILT_SHARED_LIBRARY)

include $(CLEAR_VARS)
LOCAL_MODULE    := testLib
LOCAL_SRC_FILES := lib.c

LOCAL_SHARED_LIBRARIES += libcurl

include $(BUILD_SHARED_LIBRARY)

这是我的c类：

#include "curl/curl.h"
#include "lib.h"

JNIEXPORT jint JNICALL Java_com_example_test_1libcurlandroidlib_Lib_getTestNumber
  (JNIEnv *env , jclass clazz)
{
    return 99;
}

问题是使用curl / curl.hinclude命令。我也尝试过，但它没有找到它：

The issue is with the "curl/curl.h" include command. I have also tried as but it does not find it either:

jni/lib.c:2:23: fatal error: curl/curl.h: No such file or directory
#include "curl/curl.h"

我有我的libcurl.so文件在JNI文件夹内的lib文件夹内，在构建时生成相同（我认为）文件到应用程序根目录下的libs文件夹：

I have my libcurl.so file inside a lib folder inside the JNI folder, which at build time generates the same (I think) file into the libs folder at the root of the app:

>

有没有人知道为什么我不能得到一个curl.h的引用，或者我必须做什么才能保持这个库？

Does anyone have any idea why I am not able to get a referece to curl.h, or what I have to do to get a hold of this library?

谢谢！

推荐答案

jni / lib.c：2：23：fatal error：curl / curl.h：没有此类文件或目录

jni/lib.c:2:23: fatal error: curl/curl.h: No such file or directory

为了使用这个库，你不仅需要编译的.so文件，还需要一组通常由头文件提供的函数原型（也许是数据类型定义）。

To make use of this library, you need not only the compiled .so file, but also a set of function prototypes (and perhaps data type definitions) customarily provided by a header file.

使用定义良好的库安装，这些将在二进制文件旁边的路径中提供 - 即，您将有一些curlibrary /lib/libcurl.so和其旁边的curlibrary / include / curl / curl.h

With a well-defined library installation, these would be provided in a path adjacent to the binary - ie, you would have some "curlibrary/lib/libcurl.so" and next to it a "curlibrary/include/curl/curl.h"

为了使这个工作，你需要添加curl的路径include目录到你的编译器命令行，可能是通过将它添加到你的Android.mk

To make that work, you would add the path of curl's include directory to your compiler command line, presumably by adding it to your Android.mk

LOCAL_C_INCLUDES := curlibrary/include

或任何保存它的地方。

使用include路径，在代码中对库的引用需要括在尖括号中，而不是双引号，即

To make use of the include path, your references to the library in code need to be enclosed in angle brackets, not double quotes, ie

#include <curl/curl.h>  //this searches the include path

而不是

#include "curl/curl.h"  //while this specifies a location relative to this source file

在一个更加飞越的上下文中，您可能没有真正定义安装，而只是一个.so文件（希望与您的Android ABI），以及您提取或甚至重新创建的头文件。在这种情况下，你可能更偶然地在项目源中的某处折腾curl.h，并通过特定的引用路径包含它，因为你在尝试做。如果路径是正确的，它会工作 - 但它打破了清洁的设计层次结构，并且如果卷曲的api在未来改变，可能导致混乱。

In a more fly-by-night context you may not really have a well-defined installation, but simply a .so file (hopefully compatible with your Android ABI) that you want to use, and a header file that you have either extracted or even re-created. In that case, you might more haphazardly toss "curl.h" somewhere in your project source, and include it via a specific quoted path as you were trying to do. Provided that path is correct, it will work - but it breaks the clean hierarchy of design, and could cause confusion if the api of curl ever changes in the future.

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