Question

For an Android application, I have implemented an external function in C, which I would like to use in two separate classes.

In the first class (my main Activity UI), I call the appropriate loadLibrary:

System.loadLibrary(...);

In the same class, I define the function as native:

public native int dissectPacket(byte[] header, byte[] data, int encap);

After doing this, I can call the native function with no problem in the first class. I do not get any unsatisfied link error.

Now, I want to use this function in another class. I figure I do not need to load the library again. In the second class, at the bottom, I also define:

public native int dissectPacket(byte[] header, byte[] data, int encap);

However, when I try to use the native function in the second class, I get:

07-22 23:13:13.083: ERROR/AndroidRuntime(6737): Caused by: java.lang.UnsatisfiedLinkError: dissectPacket

What is the proper way to use the function in both classes? If I do not redefine the function as native in the second class (called Packet), I get the error:

The method dissectPacket(byte[], byte[], int) is undefined for the type Packet

BTW, I do NOT want to use: class1.dissectPacket(…); I am trying to avoid passing the class.

Answer 1

You defined actually two separate functions. One for the first class and another one for the second. They will need two separate JNI stubs. You, probably, only have stub and implementation for the first one.

JNI and Java, in general, always refer to methods of the specific class.