Android之JNI实例一--简单的Java调用Native方法

1.MainActivity.java

package com.yutao.jni;

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

public class MainActivity extends Activity {

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

System.out.println(stringFromJNI());
}

public native String stringFromJNI();

static {
System.loadLibrary("TestJNI01");
}

}

2.通过javah命令自动生成头文件
进入到目录/workspace/TestJNI01/bin/classes

在终端中输入：javah -jni com.yutao.jni.MainActivity，就会生成com_yutao_jni_MainActivity.h文件

3.TestJNI01.c

#include <jni.h>

jstring Java_com_yutao_jni_MainActivity_stringFromJNI(JNIEnv *env, jobject object)
{
return (*env)->NewStringUTF(env, "Hello from JNI !");
}
4.Android.mk
LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)

LOCAL_MODULE := TestJNI01
LOCAL_SRC_FILES := TestJNI01.c

include $(BUILD_SHARED_LIBRARY)

5.生成共享库文件
新建jni文件夹，把TestJNI01.c和Android.mk放到这个目录下，执行ndk-build命令，就会在libs/armeabi/libTestJNI01.so

现在可以运行app程序，并能够看到log的输出。结束