Going Native with the NDK - Beginning Android Games - page 638

@Override
public void update( float deltaTime) {
}
@Override
public void present( float deltaTime) {
}
@Override
public void pause() {
}
@Override
public void resume() {
}
@Override
public void dispose() {
}
}
}
All the important stuff happens in the screen's constructor. We start off by creating a small
float[] array with some dummy values and a direct ByteBuffer instance that can hold 12 bytes,
or 4 floats. We also make sure that the ByteBuffer instance uses native byte order, so that we
don't run into some nasty issues when we pass it to our C/C++ code.
We then copy over three floats from the float[] array, starting at index 1, to our ByteBuffer
instance. The final few lines output the copied floats via our native logging method.
Executing this code on a device will output the following in LogCat:
08-15 17:28:31.953: V/JniUtilsTest(1901): 554.3
08-15 17:28:31.953: V/JniUtilsTest(1901): 348.6
08-15 17:28:31.953: V/JniUtilsTest(1901): 499.3
Exactly what we were expecting. Let's quickly modify the Vertices and Vertices3 classes to use
our new, faster copy() method.
Modifying the vertices classes starts with a problem: the JniUtils class is not in the
com.badlogic.androidgames.framework package; instead, it is in the
com.badlogic.androidgames.ndk package. Let's move it to the framework package so
we can reuse it.
This leads to a new problem. Our C/C++ header and source file rely on the fact that the JniUtils
class is in the ndk package. Now that we moved it to the framework package, we have to modify
the header and source file accordingly. The first thing we need to do is call javah again. This will
update the jniutils.h file. Next, we have to copy the new function names to the jniutils.cpp
file. Finally, we need to recompile the shared libraries by invoking ndk-build . Quite a bit of work
for such a small change.