Develop Reference

Undefined reference to 'jniRegisterNativeMethods' Android NDK

I'm trying to build the .so file from available NDK project. But I encounter the
undefined reference to 'jniRegisterNativeMethods' error when I try to compile the code using cmd with ndk-build
Here I'm posting the block of that execution
Android NDK: WARNING:jni/Android.mk:gba: non-system libraries in linker flags: -lnativehelper
Android NDK: This is likely to result in incorrect builds. Try using LOCAL_STATIC_LIBRARIES
Android NDK: or LOCAL_SHARED_LIBRARIES instead to list the library dependencies of the
Android NDK: current module
[armeabi] Compile++ arm : gba <= emulator.cpp
[armeabi] SharedLibrary : libgba.so
C:/sdk/android-ndk-r10e-windows-x86_64/android-ndk-r10e/toolchains/arm-linux-androideabi-4.8/prebuilt/windows-x86_64/bin/../lib/gcc/arm-linux-androideabi/4.8/../../../../arm-linux-androideabi/bin/ld.exe: error: cannot find -lnativehelper
jni/gbalib/nativehelper/JNIHelp.h:108: error: undefined reference to 'jniRegisterNativeMethods'
collect2.exe: error: ld returned 1 exit status
make.exe: *** [obj/local/armeabi/libgba.so] Error 1
E:\Android-Projects-Archieve\Library-Archives\gameboid>
I expect it to build an .so file called libgba.so Let me know in the comments if you need more info to look into this issue. Thanks in advance.

Compiling stressapptest on NDK for Android

I am currently working on trying to compile the stressapptest (link: https://github.com/stressapptest/stressapptest) using the NDK environment, and for some reason, I'm having a hard time. These are the steps that I have taken:
Clone the repository onto my computer
Added a jni folder and moved all the files into it
Created an Application.mk file
Opened PowerShell from the location of my jni folder and execute ndk-build. This is the error I'm getting:
PS C:\Users\...\Desktop\stressapptest-master\stressapptest-master> ndk-build
Android NDK: APP_PLATFORM not set. Defaulting to minimum supported version android-16.
[arm64-v8a] Compile++ : stressapptest <= main.cc
In file included from jni/src/main.cc:17:
jni/src/sattypes.h:25:10: fatal error: 'algorithm' file not found
#include <algorithm>
^~~~~~~~~~~
1 error generated.
make: *** [obj/local/arm64-v8a/objs/stressapptest/src/main.o] Error 1
Is there anything else that I need in order to compile this to run on an Android system?

Set APP_STL to c++_shared in your Application.mk. ndk-build does not use any STL by default.

android ndk project having error when loading the library

i am very new to the android ndk and opencv
but i have already run some samples/tutorials of opencv projects in Eclipse
therefore the opencv library should not be a problem
Here i want to run this camera project from github, i think it should work
After I downloaded it and import it into the Eclipse,
I encountered a problem :
When I run it it stops and finishes because the library cannot be loaded in the CameraActivity.
-> System.loadLibrary("PanoHDR");
I have tried to search the web for solutions but they either didn't work or I didn't understand them.
Do I need to do something like "ndk-build" at somewhere to make it work?
Could someone please help me? I cannot find any solution.
here is the default android.mk
LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
# Tegra optimized OpenCV.mk
include /Users/milmil/Documents/NVPACK/OpenCV-2.4.5-Tegra-sdk-r2/sdk/native/jni/OpenCV-tegra3.mk
# Linker
LOCAL_LDLIBS += -llog
# Our module sources
LOCAL_MODULE := PanoHDR
LOCAL_SRC_FILES := PanoHDR.cpp Panorama.cpp HDR.cpp NativeLogging.cpp
include $(BUILD_SHARED_LIBRARY)
when i try to use ndk-build in cmd in the main dir of the project
it fails
jni/Android.mk:6: /sdk/native/jni/OpenCV.mk: No such file or directory
make: *** No rule to make target `/sdk/native/jni/OpenCV-tegra3'. Stop.
and it should be caused by this line in the Andriod.mk
include /Users/milmil/Documents/NVPACK/OpenCV-2.4.5-Tegra-sdk-r2/sdk/native/jni/OpenCV-tegra3.mk
I try to use the path of my opencv sdk
include /Android/OpenCV-3.1.0-android-sdk/OpenCV-android-sdk/sdk/native/jni/OpenCV.mk
and it returns this in the cmd
Android NDK: WARNING:jni/Android.mk:PanoHDR: non-system libraries in linker flag
s: -lopencv_java3
Android NDK: This is likely to result in incorrect builds. Try using LOCAL_S
TATIC_LIBRARIES
Android NDK: or LOCAL_SHARED_LIBRARIES instead to list the library dependenc
ies of the
Android NDK: current module
[armeabi-v7a] "Compile++ thumb": "PanoHDR <= PanoHDR.cpp"
The system cannot find the path specified.
make: *** [obj/local/armeabi-v7a/objs/PanoHDR/PanoHDR.o] Error 1
Thank you
=========================================================================
WARNING:jni/Android.mk:PanoHDR: non-system libraries in linker flag
s: -lopencv_java3
the above problem is solved by adding "OPENCV_LIB_TYPE=STATIC" in the android.mk, but still has this error "
[armeabi-v7a] "Compile++ thumb": "PanoHDR <= PanoHDR.cpp"
The system cannot find the path specified.
make: *** [obj/local/armeabi-v7a/objs/PanoHDR/PanoHDR.o] Error 1"

How to fork a Framework Library

After downloading the Android Source Code using the repo command as suggested on the page:
repo init -u https://android.googlesource.com/platform/manifest
I was able to compile the whole project without issue using make.
What I would like to do is compile my own fork of android.media.MediaPlayer, but I am lost as to how to set up the build.
I tried using ndk-build in /frameworks/base/media/libmedia, and got the following output:
Android NDK: WARNING:/home/user/android/WORKING_DIRECTORY/frameworks/base/media/jni/Android.mk:media_jni: non-system libraries in linker flags: -lpthread
Android NDK: This is likely to result in incorrect builds. Try using LOCAL_STATIC_LIBRARIES
Android NDK: or LOCAL_SHARED_LIBRARIES instead to list the library dependencies of the
Android NDK: current module
[armeabi] Compile++ thumb: audioeffect_jni <= android_media_AudioEffect.cpp
/home/user/android/WORKING_DIRECTORY/frameworks/base/media/jni/audioeffect/android_media_AudioEffect.cpp:22:23: fatal error: utils/Log.h: No such file or directory
compilation terminated.
make: *** [/home/user/android/WORKING_DIRECTORY/frameworks/base/media/obj/local/armeabi/objs/audioeffect_jni/android_media_AudioEffect.o] Error 1
How could I compile a .jar that contained libmedia and android.media.MediaPlayer so that I could simply drop it into a project and use that instead of the default android.media.MediaPlayer?

opencv.hpp not found in NDK build on Windows

I am getting some issues here while I am trying to compile my code with Cgywin.
$ /cygdrive/c/native_work/android-ndk-r8b/ndk-build
Android NDK: WARNING: Unsupported source file extensions in jni/Android.mk for module main
Android NDK: NotePaperDetector.hpp
Install : libmain.so => libs/armeabi-v7a/libmain.so
so how I can compile the .hpp file ?
Now as #mah you said I have removed it from my Android.mk but now its showing some different error -
$ /cygdrive/c/native_work/android-ndk-r8b/ndk-build
Compile++ thumb : main <= NotePaperDetector.cpp
In file included from jni/NotePaperDetector.hpp:4:0,
from jni/NotePaperDetector.cpp:1:
jni/NoteLocation.hpp:4:30: fatal error: opencv2/opencv.hpp: No such file or directory
compilation terminated.
/cygdrive/c/native_work/android-ndk-r8b/build/core/build-binary.mk:255: recipe for target `obj/local/armeabi-v7a/objs/main/NotePaperDetector.o' failed
make: *** [obj/local/armeabi-v7a/objs/main/NotePaperDetector.o] Error 1

With the latest NDK releases you don't need Cygwin at all.
By the way a GNU/Linux platform is always the best for Android developers.