Android.mk中LOCAL_EXPORT_C_INCLUDES的作用
Android.mk中LOCAL_EXPORT_C_INCLUDES的作用
?
????? NDK中的说明是这样说明的：
?
?????
III. Exporting headers for prebuilt libraries:----------------------------------------------The example above was called 'naive' because, in practice, the code infoo-user.c is going to depend on specific declarations that are normallyfound in a header file distributed with the prebuilt library (e.g. "foo.h").In other words, foo-user.c is going to have a line like: #include <foo.h>And you need to provide the header and its include path to the compilerwhen building the foo-user module.A simple way to deal with that is to use exports in the prebuilt moduledefinition. For example, assuming that a file "foo.h" is located underthe 'include' directory relative to the prebuilt module, we can write: include $(CLEAR_VARS) LOCAL_MODULE := foo-prebuilt LOCAL_SRC_FILES := libfoo.so LOCAL_EXPORT_C_INCLUDES := $(LOCAL_PATH)/include include $(PREBUILT_SHARED_LIBRARY)The LOCAL_EXPORT_C_INCLUDES definition here ensures that any module thatdepends on the prebuilt one will have its LOCAL_C_INCLUDES automaticallyprepended with the path to the prebuilt's include directory, and will thusbe able to find headers inside that.
?
??????? 如果看不懂就看这个博客的翻译吧，非常好：
?
??????? http://www.cnblogs.com/qq78292959/archive/2011/11/02/2232962.html
?
?????? 感谢这哥们将NDK的文档都翻译了，高质量，高水平。
?
?????? 我当时情况是，如果我们自己的c或cpp中如果引用了其他库使用的头文件，那么例如：
?
????? 我的jni_main.cpp中#include "openssl/ssl.h"，那么我拷贝到jni下的应该是openssl目录，里面包含这这个
?
ssl.h头文件，那么我就不用使用这个LOCAL_EXPORT_C_INCLUDES也可以正常编译使用。很明显是正确的。
??????? 那么这个东西是干嘛用的呢？我就猜想，一般大家都把头文件放到叫include的目录中，比如Android源码里的external/openssl/下面的include中有/openssl/ssl.h，看来如果尊重这个习惯的话，那么使用这个变量不就很好了嘛，可以让ndk去include下面去找openssl啊，如果还要其他的模块，把他们的头文件也放到include中，也能集中啊，多么美好的东西啊。
?
??????? 实践一下吧：
?
??????? 1.先将external/openssl/下面的include目录整体拷贝到工程的jni目录下，然后在Android.mk中修改如下：
?
????????
dr@dr-OptiPlex-3010:~/workspace/OpensslTest/jni$ ~/android-ndk-r5b/ndk-buildCompile++ thumb : jni_openssltest <= jni_main.cpp/home/dr/workspace/OpensslTest/jni/jni_main.cpp:3:25: error: openssl/ssl.h: No such file or directory/home/dr/workspace/OpensslTest/jni/jni_main.cpp: In function 'jint Java_com_example_openssltest_JniTest_getInit(JNIEnv*, _jobject*)':/home/dr/workspace/OpensslTest/jni/jni_main.cpp:15: error: 'SSL_library_init' was not declared in this scopemake: *** [/home/dr/workspace/OpensslTest/obj/local/armeabi/objs/jni_openssltest/jni_main.o] Error 1dr@dr-OptiPlex-3010:~/workspace/OpensslTest/jni$
?
??????? 好了，验证了。再次感谢那哥们的翻译，真是太好了。
?
?
?