Problem in compiling android-ndk code

I am facing an issue and would like开发者_运维问答 to know why this is happening.

I have a project which consists of a Java file and some JNI & C++ code files. I am building JNI and C++ code through cygwin which is part of android ndk-tools. Below is my Android.mk file

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)
LOCAL_MODULE := cube
LOCAL_CFLAGS := -DANDROID_NDK
LOCAL_SRC_FILES := Testing.cpp
LOCAL_LDLIBS := -lGLESv1_CM
include $(BUILD_SHARED_LIBRARY)


include $(CLEAR_VARS)
LOCAL_MODULE := jni_opengl
LOCAL_SRC_FILES := jni_openglcube.cpp
LOCAL_SHARED_LIBRARIES := cube
include $(BUILD_SHARED_LIBRARY)

In script above cube module is written in standard C++ which do some opengl stuff and jni_opengl is written in JNI. Above script compiles fine but when I change line 8 include $(BUILD_SHARED_LIBRARY) to include $(BUILD_STATIC_LIBRARY) I start getting error regarding opengl methods not found in Testing.cpp.

My question is why in case of shared library, android is able to find the references of opengl related method and why not when I change it to static library?

Symbols needed in shared libraries are sometimes looked up at runtime. So, I think you run into the same problem, but now at runtime not link time. See if the code with the shared library runs.

I don't think you need to have:

LOCAL_LDLIBS := -lGLESv1_CM

for your static library.

You will need to move it to your shared library section. The static section will be fine without it.

Don't forget to change:

LOCAL_SHARED_LIBRARIES := cube

to

LOCAL_STATIC_LIBRARIES := cube

A static library is just a bunch of .o files appended together, so it doesn't get 'linked' in the same way a shared library does.

Your final Android.mk should look something like this:

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)
LOCAL_MODULE := libcube
LOCAL_CFLAGS := -DANDROID_NDK
LOCAL_SRC_FILES := Testing.cpp
include $(BUILD_STATIC_LIBRARY)


include $(CLEAR_VARS)
LOCAL_MODULE := jni_opengl
LOCAL_SRC_FILES := jni_openglcube.cpp
LOCAL_STATIC_LIBRARIES := libcube
LOCAL_LDLIBS := -lGLESv1_CM -ldl -llog
include $(BUILD_SHARED_LIBRARY)