If it’s an object method, you need to pass the object to CallObjectMethod: jobject result = env->CallObjectMethod(obj, messageMe, jstr); What you were doing was the equivalent of jstr.messageMe(). Since your is a void method, you should call: env->CallVoidMethod(obj, messageMe, jstr); If you want to return a result, you need to change your JNI signature (the … Read more
In order for System.loadLibrary() to work, the library (on Windows, a DLL) must be in a directory somewhere on your PATH or on a path listed in the java.library.path system property (so you can launch Java like java -Djava.library.path=/path/to/dir). Additionally, for loadLibrary(), you specify the base name of the library, without the .dll at the … Read more
You need to add LOCAL_LDLIBS := -llog to Android.mk
From the Java language spec: It is a compile time error to import a type from the unnamed package. You’ll have to access the class via reflection or some other indirect method.
It is possible to create a single JAR file with all dependencies including the native JNI libraries for one or more platforms. The basic mechanism is to use System.load(File) to load the library instead of the typical System.loadLibrary(String) which searches the java.library.path system property. This method makes installation much simpler as the user does not … Read more
JNA does not support mapping of c++ classes, so if you’re using c++ library you will need a jni wrapper If you need a lot of memory copying. For example, you call one method which returns you a large byte buffer, you change something in it, then you need to call another method which uses … Read more
Here’s a a couple of useful link that I found when I started with JNI http://en.wikipedia.org/wiki/Java_Native_Interface http://download.oracle.com/javase/1.5.0/docs/guide/jni/spec/functions.html concerning your problem you can use this JNIEXPORT void JNICALL Java_ClassName_MethodName(JNIEnv *env, jobject obj, jstring javaString) { const char *nativeString = env->GetStringUTFChars(javaString, 0); // use your string env->ReleaseStringUTFChars(javaString, nativeString); }
First, ensure that your version of Eclipse and JDK match, either both 64-bit or both 32-bit (you can’t mix-and-match 32-bit with 64-bit). Second, the -vm argument in eclipse.ini should point to the java executable. See http://wiki.eclipse.org/Eclipse.ini for examples. If you’re unsure of what version (64-bit or 32-bit) of Eclipse you have installed, you can determine … Read more
Update. This answer is quite popular even four years after I write it, in this four years a lot of things has changed, so I decided to update my answer to fit better our current reality. The answer idea does not change; the implementation has changed a little. My English also has changed, it has … Read more
If you’ve examined the documentation and still have questions that should be part of your initial question. In this case, the JNI function in the example creates a number of arrays. The outer array is comprised of an ‘Object’ array creating with the JNI function NewObjectArray(). From the perspective of JNI, that’s all a two … Read more