Develop Reference

Using JsonCpp on X-Cross platform library

I'm making a library in C++ with OpenCV and JsonCpp towards building a library for Android and iOS.
On testing my library for Android, I'm making the JNI files but when I try to load the library I'm getting
java.lang.UnsatisfiedLinkError: dlopen failed: cannot locate symbol
"_ZN4Json6WriterD2Ev" referenced by "libXYZ.so"...
and that's because I think I'm not building my Json library very well.
The library that I use is this one: https://github.com/open-source-parsers/jsoncpp
My Android.mk is:
LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
OPENCV_CAMERA_MODULES:=off
OPENCV_INSTALL_MODULES:=on
include $(LOCAL_PATH)/jsoncpp/Android.mk
include /Users/localmac/Desktop/AndroidDevelopment/OpenCV-2.4.9-android-sdk/sdk/native/jni/OpenCV.mk
OPENCV_LIB_TYPE:=SHARED
LOCAL_C_INCLUDES += $(LOCAL_PATH)
LOCAL_C_INCLUDES += /Users/localmac/mylibrary/OpenCVtry/
LOCAL_C_INCLUDES += /Users/localmac/Desktop/RD/OpenCVtry/Libraries/jsoncpp-master/include
LOCAL_ALLOW_UNDEFINED_SYMBOLS := true
LOCAL_MODULE := libXYZ
LOCAL_SRC_FILES := androidClass.cpp main.cpp utils.cpp
LOCAL_LDLIBS += -llog -ldl
include $(BUILD_SHARED_LIBRARY)
I have no idea of how to do this.
Thank you in advance.
EDIT it's not the NDK Compiling's fault.
Even if I compile the JsonCpp, I get the
java.lang.UnsatisfiedLinkError: dlopen failed: cannot locate symbol "_ZN4Json6WriterD2Ev" referenced by "libXYZ.so"...
EDIT My jsoncpp/Android.mk :
LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_CPP_EXTENSION := .cpp LOCAL_MODULE := libJsoncpp
LOCAL_C_INCLUDES := $(LOCAL_PATH)/jsoncpp/include
LOCAL_SRC_FILES := src/lib_json/json_reader.cpp \
src/lib_json/json_value.cpp \
src/lib_json/json_writer.cpp
include $(BUILD_SHARED_LIBRARY)

You're not linking against Jsoncpp in your makefile. You should add the following line:
LOCAL_SHARED_LIBRARIES := libJsoncpp
before the last include $(BUILD_SHARED_LIBRARY).
You must specify module names for this variable (and its sister LOCAL_STATIC_LIBRARIES), that is, what you specified for the LOCAL_MODULE variable.
Also, that spares you from specifiying the includes in the LOCAL_C_INCLUDE variable (as the makefile will include them directly when specifying the library in the variable I mentioned at the top of my post).
EDIT: For the sake of completeness, I'll add that you can specify multiple libraries like that:
LOCAL_SHARED_LIBRARIES = libJsoncpp \
libOpenCV \
...
and the same goes for LOCAL_STATIC_LIBRARIES.

How to link .so file in android

I have two projects. The output of first one is libtest.so file. Using this shared object file in the 2nd project, i want to generate final android executable, AndroidExe.
I generated libtest.so and its Android.mk is given below
LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_CFLAGS := -g
LOCAL_ARM_MODE := arm
LOCAL_MODULE :=test
LOCAL_SRC_FILES := test.c
export LD_LIBRARY_PATH=/data/local/tmp
include $(BUILD_SHARED_LIBRARY)
Here the problem i am facing is that, i don't know how to link this .so file in my final executable project. In this final project, i am using one of the function (sum(a,b)) defined in the .so lib.While do build, showing error undefined reference to 'sum'.Its Android.mk file is given below:
LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_CFLAGS := -g
LOCAL_ARM_MODE := arm
LOCAL_MODULE :=AndroidExe
LOCAL_SHARED_LIBRARIES := libtest.so
LOCAL_SRC_FILES := AndroidExe.c
include $(BUILD_EXECUTABLE)

just check ndk documentation and try some of the samples.

Build shared library linking to other not standard shared libarary

I have some two shared libraries and header for them.
I want to build third shared library using functions from previous two libs.
Have problem with makefile i think. When i try to build receive this:
Android NDK: /cygdrive/d/.../jni/Android.mk: Cannot find module with tag 'shared1' in import path
Android NDK: Are you sure your NDK_MODULE_PATH variable is properly defined ?
Android NDK: The following directories were searched:
Android NDK:
/cygdrive/d/.../jni/Android.mk:36: *** Android NDK: Aborting. . Stop.
structure of my project:
jni/
- myfile.c
- Android.mk
jni/dec/
- lot of header files
jni/enc/
- lot of header files
libs/armeabi/
- shared1.so
- shared2.so
also Android.mk sourse:
LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_C_INCLUDES := \
$(LOCAL_PATH)/dec \
$(LOCAL_PATH)/enc
LOCAL_SHARED_LIBRARIES := shared1 shared2
LOCAL_MODULE := mylib
LOCAL_SRC_FILES := myfile.c
LOCAL_LDLIBS += -lOpenSLES
LOCAL_LDLIBS += -llog
LOCAL_LDLIBS += -landroid
include $(BUILD_SHARED_LIBRARY)
$(call import-module, shared1)
$(call import-module, shared2)

Take a look to this question: Android JNI APK Packing
You need to give another name for libs/armeabi/ folder to avoid conflicts with NDK build and add the following code before the include $(CLEAR_VARS) statement:
include $(CLEAR_VARS)
LOCAL_MODULE:=shared1
LOCAL_SRC_FILES:=3rdparty_libs/shared1.so
include $(PREBUILT_SHARED_LIBRARY)
include $(CLEAR_VARS)
LOCAL_MODULE:=shared2
LOCAL_SRC_FILES:=3rdparty_libs/shared2.so
include $(PREBUILT_SHARED_LIBRARY)

As I understand it, the correct method is to use ndk-build and not invoking the compiler directly.
In Android.mk you need to specify a module for each static library you want to compile, and then specify that your shared library should use it.
Example of a modified Android.mk file of the hello-jni sample project:
LOCAL_PATH := $(call my-dir)
# Define vars for library that will be build statically.
include $(CLEAR_VARS)
LOCAL_MODULE := <module_name>
LOCAL_C_INCLUDES := <header_files_path>
LOCAL_SRC_FILES := <list_of_src_files>
# Optional compiler flags.
LOCAL_LDLIBS = -lz -lm
LOCAL_CFLAGS = -Wall -pedantic -std=c99 -g
include $(BUILD_STATIC_LIBRARY)
# First lib, which will be built statically.
include $(CLEAR_VARS)
LOCAL_MODULE := hello-jni
LOCAL_STATIC_LIBRARIES := <module_name>
LOCAL_C_INCLUDES := <header_files_path>
LOCAL_SRC_FILES := hello-jni.c
include $(BUILD_SHARED_LIBRARY)
If you want control over which modules to compile when you run ndk-build you can create create a Application.mk file (in the same directory as Android.mk) and list all the modules as in the following example:
APP_MODULES := <module_name_1> <module_name_2> ... <module_name_n>
I think it Helps you

ndk-build failed: No rule to make target pjsua_wrap.cpp needed by pjsua_wrap.o

I have been trying to build the CSipSimple in my Win7 (X64) machine for couple of days.
I am using cygwin for building the code. But currently it is displaying me the below image.
Please give me some suggestions.

It would be useful if you showed us your "android.mk" file. Here is an example of an android.mk file which builds a library called "mylib" from 2 cpp files:
LOCAL_PATH := $(call my-dir)
LOCAL_ARM_MODE :=arm
include $(CLEAR_VARS)
LOCAL_MODULE := mylib
LOCAL_SRC_FILES := \
mysource1.cpp \
mysource2.cpp \
LOCAL_LDLIBS := -L$(SYSROOT)/usr/lib -lz -lm -llog
include $(BUILD_SHARED_LIBRARY)

Error in linking C++ static library with android ndk(Error: file format not recognized)

I am trying to include static cpp library in android. This library is already compiled(on mac os) and i have its include files.
Here is my Android.mk file
LOCAL_PATH := $(call my-dir)
include $(call all-subdir-makefiles)
include $(CLEAR_VARS)
LOCAL_MODULE:= utils
LOCAL_SRC_FILES:= libUtils.a
LOCAL_EXPORT_C_INCLUDES := $(LOCAL_PATH)/utils
include $(PREBUILT_STATIC_LIBRARY)
include $(CLEAR_VARS)
LOCAL_MODULE := sample
LOCAL_SRC_FILES := sample_cpp.cpp
LOCAL_EXPORT_C_INCLUDES := $(LOCAL_PATH)
LOCAL_STATIC_LIBRARIES := utils
LOCAL_LDLIBS := -llog
include $(BUILD_SHARED_LIBRARY)
and here is Application.mk file
APP_STL := stlport_static
APP_CPPFLAGS = -fexceptions
but whenever it try to compile it using NDK i get the error
(Path of file)/libUtils.a: file not recognized: File format not recognized
collect2: ld returned 1 exit status

From the comments and so on it sounds like you trying to use a non arm version of the library. You should build the library with the ndk. The documentation has even documentation on how to do that.
For example building sigc++ could be like (from a project of mine, where sigc++ resides in the sigc++ subdirectory)
# SIGC++ Library built as static library
LOCAL_MODULE := sigc
LOCAL_PATH = $(CURRENT_DIR)
LOCAL_CPP_EXTENSION := .cc
LOCAL_SRC_FILES := sigc++/signal.cc sigc++/signal_base.cc sigc++/trackable.cc
LOCAL_SRC_FILES += sigc++/functors/slot_base.cc sigc++/adaptors/lambda/lambda.cc
LOCAL_SRC_FILES += sigc++/connection.cc sigc++/functors/slot.cc
LOCAL_C_INCLUDES := sigc++
include $(BUILD_STATIC_LIBRARY)
But you should really read how the compiling linking works. I am afraid building for android with ndk is more low level than using Xcode or Msvc.