Java and OpenJDK are trademarks or registered trademarks of Oracle and/or its affiliates. Return (*env)->NewStringUTF(env, "Hello from JNI !Ĭontent and code samples on this page are subject to the licenses described in the Content License. That is, the string that the function on the Java side had requested. The following line calls the VM API (*env), and passes it a return value: Jobject is a pointer to the implicit this object passed from Hellojni/src/com/example/hellojni/HelloJni.java. This name refers to a Javaįunction called stringFromJNI(), which resides in Java_com_example_hellojni_HelloJni_stringFromJNI. After the last underscore, append the function name.įollowing these rules, this example uses the function name.Use underscores in place of forward slashes.Describe the filepath relative to the top-level source directory.Java function name and the path to the file containing it. It is not actually a string, but aĪfter jstring comes the function name, which is based on the The return type, jstring, is a data type defined This declaration corresponds to the native function declared in the Java_com_example_hellojni_HelloJni_stringFromJNI( JNIEnv* env, Returns a string that the Java side requested). The hello-jni.c file is located in hello-jni/jni/. They are presented here in the order in which they are used, rather than by The source code contains three lines of particular interest to the NDK user. It callsĪ function to retrieve a string from the native side, then displays it on the screen. The helloJNI.java file is located in hellojni/src/com/example/hellojni/. In thisĮxample, the build system builds for all supported architectures.įor more information about the Application.mk file, and how to use it, see This line tells the build system the CPU and architecture against which to build. Library is libhello-jni.so, once the build system adds theįor more information about what the Android.mk file does, and how to use it, see With the name of the shared library to build. The following two lines provide the name of the native source file, along Of ndk-samples repo, inside android-mk branch. In particular, it showcases the ndkhelper helper class, a collection of native helper. And it uses handmade style bat file to build, install and run application, no IDE required.This sample guides you through hello-jni, a minimalĬ/C++ application built with the NDK. This sample uses the OpenGL library to render the iconic Utah teapot. I've put super simple OpenGL ES 2 example on my github: It has only C code and uses NativeActivity so I don't need to use any Java code. But you don't need to change your native code a lot, you can still use it, but simply extend NativeActivity class.ītw, if you are on Windows, you can use Microsoft Visual Studio 2015 to build and debug Android NDK applications: When NativeActivity won't be enough and you'll want to access more Android API's then that must be done in Java (it's possible to do it native code with JNI, but it is huge pain, simple one line of Java code can be tens or hundreds lines of code in C). Take a look also at other examples in android-ndk repo: Here is its reference documentation: įor basic example take a look at native-activity sample:īut I suggest to start with even simpler example "hello-jni" to understand how everything works together: h file, source comes with NDK) called native_app_glue that wraps NativeActivity API's with a bit nicer interface. NDK also comes with tiny library (just one. Here is documentation about NativeActivity: On Command Line: set up ANDROIDHOME and ANDROIDNDKHOME to your SDK and NDK path, cd to individual sample dir, and do 'gradlew assembleDebug'. In this case you will be writing native code in shared library which will be called by NativeActivity for various events - like applications started, input events, application closed, low memory, etc. With Android Studio: 'Open An Existing Android Studio Project' or 'File' > 'Open', then navigate to & select project's adle file. Web implementation sample code is located in packages > wallet-card > sample directory. It consists of Javascript API source code and web implementation sample code. The first thing we can do is to check if it even compiles with the default before we start thinking too far ahead on those complicated projects. This sample code shows how to implement Samsung Wallet Card Service in Web. Now, we have all the basic NDK tools ready for native code development in Android. But there is built in class called NativeActivity that sets everything up in Java, so you can use only native code. Web Integration Sample Code (ZIP) v1.0.0. It will be still there, because all applications on Android starts up as Java. For basic functionality like getting window up, getting input events, doing some OpenGL rendering and outputting sound you can do without Java.
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