Android JNI で C/C++ のポインタを Java に渡す。（Java 側のソース）

com.example.ndkpointer.MainActivity.java

package com.example.ndkpointer;

import android.app.Activity;
import android.os.Bundle;

public class MainActivity extends Activity {

	static {
		System.loadLibrary("NdkPointer");
	}

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		nativeMethod();
	}

	public static native void nativeMethod();
	public static native void callback(long cppPointer);

	public static void asyncProc(final long cppPointer) {

		Thread t = new Thread(new Runnable() {

			@Override
			public void run() {
				// 時間のかかる処理
				try {
					Thread.sleep(3000);
				} catch (InterruptedException e) {
					e.printStackTrace();
				}
				callback(cppPointer);
			}
		});

		t.start();
	}

}