Android JNI_OnLoad

http://zhidao.baidu.com/link?url=VZS2_Nx-prapV2fQ_uUyqTghX4hNu-GKR8MdaKlwiGOHz3DR52EsVlDeyuIkBduu_IPD8WnGDFzf3nR2cYClsyZfUXrcgdYkoOiGKZ5dvg3
http://blog.chinaunix.net/uid-26993600-id-3303022.html http://blog.sina.com.cn/s/blog_7a2ffd5c01013vrv.html http://blog.csdn.net/imyfriend/article/details/9117917
#include <string.h>
#include <jni.h>
#include <assert.h>

char * s1 = "hello s1";

extern "C" {
jstring Java_com_example_helloworld_MainActivity_stringFromJNI( JNIEnv* env, jobject thiz )
{
return env->NewStringUTF(s1);
}
}

JNIEXPORT jstring JNICALL native_hello(JNIEnv *env, jclass clazz)
{
return env->NewStringUTF("hello world returned.");
}

#define JNIREG_CLASS "com/example/helloworld/MainActivity"

static JNINativeMethod gMethods[] = {
{ "hello", "()Ljava/lang/String;", (void*)native_hello },
};

static int registerNativeMethods(JNIEnv* env, const char* className,
JNINativeMethod* gMethods, int numMethods)
{
jclass clazz;
clazz = env->FindClass(className);
if (clazz == NULL) {
return JNI_FALSE;
}
if (env->RegisterNatives(clazz, gMethods, numMethods) < 0) {
return JNI_FALSE;
}
return JNI_TRUE;
}

static int registerNatives(JNIEnv* env)
{
if (!registerNativeMethods(env, JNIREG_CLASS, gMethods,
sizeof(gMethods) / sizeof(gMethods[0])))
return JNI_FALSE;
return JNI_TRUE;
}

JNIEXPORT jint JNICALL JNI_OnLoad(JavaVM* vm, void* reserved)
{
JNIEnv* env = NULL;
jint result = -1;
if (vm->GetEnv( (void**) &env, JNI_VERSION_1_4) != JNI_OK) {
return -1;
}
assert(env != NULL);

if (!registerNatives(env)) {
return -1;
}

result = JNI_VERSION_1_4;

s1 = "hellow s2";

//return -1;

return result;
}

package com.example.helloworld;

import android.widget.TextView;

import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;

public class MainActivity extends ActionBarActivity {

private TextView textview1;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
textview1 = (TextView)findViewById(R.id.textview1);
textview1.setText(stringFromJNI());
textview1.setText(hello());
}

public native String stringFromJNI();
public static native String hello();

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