I have function implemented in C++ with several parameters and outputs. I want to use this function in my Android Studio Java code as a black box to pass necessary arguments and get results. The problem is that C++ function uses several libraries such as OpenCV together with other C++ implemented functions. I read about NDK and JNI and tried to do simple "Hello from C++" function call and it works. However, I do not understand how to install all libraries to C++ and how to put all necessary C++ codes.
You can find nice tutorial about JNI here.
Related
I have used a native C++ DLL in Xamarin.Android using [DLLImport] but I am getting exception System.DllNotFoundException. I have used same way as I do in C#. Plz provide me some simple code which explains all steps so that I can know if something extra has to be done for Xamarin.Android.
If you importe your library and you linked it in your project
you should use.
[DllImport ("__Internal")]
Instead of using a name of your library.
[DllImport ("LibraryName")]
We have developed an iPad application where the core logic is written in CPP code, so that we can use the same code files/libraries to other platforms.
Now I want to use those files and develop similar Android application, but unable to create .so files and integrate paths in Android.mk files and all. I am basically an iOS developer, this is first time I am looking into Android NDK.
Can anyone help and guide if there is any straight forward steps to it.
I have already gone through android developers site and few other tutorial sites. But none of those worked for me.
Require easy-clear steps to call cpp method in java, if I do have few cpp files and .a libraries with me already.
You aren't very specific at the step you are stuck at.
Here's a very quick explanation on how to call native code from java (android) :
first create a method to be exported by the native and called by java (this uses JNI, so google JNI , JNIEXPORT)
once you have this method defined in your native code, it's time to create a shared library (.so) file , using the compiler that comes in the NDK (because you are compiling for android ). You will need to compile for the correct architecture of the device (armeabiv7s is the most common now days).
you need to add the library file in your app.apk inside the armeabi folder (more details in NDK tutorials).
inside your java code you will need to load the shared library via the System.loadLibrary(LIBRARY_NAME);
inside your java code you will need to have defined static native methods that are in pair with the methods you exported from your CPP code
Quick tips :
use C functions,not CPP , since CPP will be mangled in the resulting shared library. In other words, you will need to create a C wrapper that will call your cpp code.
look over a hello world tutorial for NDK , and work yourself from there . Here's a link to such tutorial http://trivedihardik.wordpress.com/2011/06/16/hello-world-example-using-ndk-in-android/
You will bump later on into compilation issues with the makefiles, but by then you will probably be able to be more specific with your question.
Easiest way is to use the hello-jni Android studio sample project.
There are a lot of settings and configurations, you get them from the sample that is a working unit, always easiest when starting from something working.
First run (and modify) the hello-jni and learn how the interactivity between the Java and C parts works. About everything works except environmental ANSI C/C++ stuff. You have to get things like language, country etc from Java and transfer it to the C-code. You are in US in English with "inches and gallons" in JNI.
Then to an own project you create with android studio, copy and modify from it bit by bit from hello-jni. When you have our own branded hello-JNI you can add bit by bit your own code. Often using C-dummies for testing the interactivity with the Java part is easier, then change it to the real C/C++ code of yours.
Read the Android/Android studio documentation and learn and understand. Use the Android emulators, much easier and they are good.
The project configuration stuff is by far the hardest to handle at the start. If I would make a new project today, I would start from the Hello-JNI once again.
I have a huge C++ library for image processing. I would like to use this DLL library in an Android project. How can I call methods in the C++ DLL library in Android?
Maybe you can try JavaCPP. JavaCPP will help you auto generate appropriate code for JNI, and passes it to the C++ compiler to build a native library.
For more details and examples, please seeļ¼ https://code.google.com/p/javacpp/
via JNI Java Native Interface.
using this keyword will let you find a tutorial:
http://developer.android.com/training/articles/perf-jni.html
You need the Java Native Interface (JNI)
Oracle has a great set of tutorials on it (google for them).
Also, since you tagged your question Android, I'm presuming that's the platform you need JNI on.
You'll have to look into the Native Development Kit, more info on that here: http://developer.android.com/tools/sdk/ndk/index.html
I am working on android project.I have created a native edittext.I want use native jni function
in other android c++ project for display the edittext in c++.whenever i add the headerfile of
jni and edittext,then compiler does not find.
Can you suggest me.how to add native edittext project with my own project and how to use jni function with c++.
Your suggestion will helpful.
Take your code you want to share and place it into it's own compiled library. Then you can reference it in both the android project and the c++ project and use the code in both.
How to create and use static librarys in c++
How to add libraries in C++?
Id like to use mupdf as a pdf viewer inside my own android app.
Ive been able to compile it (not easy) from instructions here , the last steps were :
ndk-build
ant debug
Now, how to call mupdf from my android project in eclipse ?
I just want to open a window with a specified PDF and a custom toolbar.
The mupdf.c is a wrapper of the native code, and the function that can be called by java code must have prefix such as com_artifex_mupdf_MuPDFCore.
In its function name Java_com_artifex_mupdf_MuPDFCore_openFile, com_artifex_mupdf_MuPDFCore is exactly the package name of the java code which declared the native functions, check out MuPDFCore.java, each native function are declared by using native keyword. Then you can use these functions like normal java methods.
BTW, mupdf is NOT thread safe, your JNI java code should be careful to use synchronized. The open source project VuDroid is also a good example to learn how to interact with mupdf via JNI.