public class MainActivity extends Activity {
public static native String test();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}javah -d ../jni 包名.MainActivity这时候刷新项目就会发现多了一个jni文件夹，里面有个.h的文件，打开就是一个c头文件
/* DO NOT EDIT THIS FILE - it is machine generated */
#include <jni.h>
/* Header for class com_example_exercise_MainActivity */
#ifndef _Included_com_example_exercise_MainActivity
#define _Included_com_example_exercise_MainActivity
#ifdef __cplusplus
extern "C" {
#endif
#undef com_example_exercise_MainActivity_MODE_PRIVATE
#define com_example_exercise_MainActivity_MODE_PRIVATE 0L
#undef com_example_exercise_MainActivity_MODE_WORLD_READABLE
#define com_example_exercise_MainActivity_MODE_WORLD_READABLE 1L
#undef com_example_exercise_MainActivity_MODE_WORLD_WRITEABLE
#define com_example_exercise_MainActivity_MODE_WORLD_WRITEABLE 2L
#undef com_example_exercise_MainActivity_MODE_APPEND
#define com_example_exercise_MainActivity_MODE_APPEND 32768L
#undef com_example_exercise_MainActivity_MODE_MULTI_PROCESS
#define com_example_exercise_MainActivity_MODE_MULTI_PROCESS 4L
#undef com_example_exercise_MainActivity_MODE_ENABLE_WRITE_AHEAD_LOGGING
#define com_example_exercise_MainActivity_MODE_ENABLE_WRITE_AHEAD_LOGGING 8L
#undef com_example_exercise_MainActivity_BIND_AUTO_CREATE
#define com_example_exercise_MainActivity_BIND_AUTO_CREATE 1L
#undef com_example_exercise_MainActivity_BIND_DEBUG_UNBIND
#define com_example_exercise_MainActivity_BIND_DEBUG_UNBIND 2L
#undef com_example_exercise_MainActivity_BIND_NOT_FOREGROUND
#define com_example_exercise_MainActivity_BIND_NOT_FOREGROUND 4L
#undef com_example_exercise_MainActivity_BIND_ABOVE_CLIENT
#define com_example_exercise_MainActivity_BIND_ABOVE_CLIENT 8L
#undef com_example_exercise_MainActivity_BIND_ALLOW_OOM_MANAGEMENT
#define com_example_exercise_MainActivity_BIND_ALLOW_OOM_MANAGEMENT 16L
#undef com_example_exercise_MainActivity_BIND_WAIVE_PRIORITY
#define com_example_exercise_MainActivity_BIND_WAIVE_PRIORITY 32L
#undef com_example_exercise_MainActivity_BIND_IMPORTANT
#define com_example_exercise_MainActivity_BIND_IMPORTANT 64L
#undef com_example_exercise_MainActivity_BIND_ADJUST_WITH_ACTIVITY
#define com_example_exercise_MainActivity_BIND_ADJUST_WITH_ACTIVITY 128L
#undef com_example_exercise_MainActivity_CONTEXT_INCLUDE_CODE
#define com_example_exercise_MainActivity_CONTEXT_INCLUDE_CODE 1L
#undef com_example_exercise_MainActivity_CONTEXT_IGNORE_SECURITY
#define com_example_exercise_MainActivity_CONTEXT_IGNORE_SECURITY 2L
#undef com_example_exercise_MainActivity_CONTEXT_RESTRICTED
#define com_example_exercise_MainActivity_CONTEXT_RESTRICTED 4L
#undef com_example_exercise_MainActivity_RESULT_CANCELED
#define com_example_exercise_MainActivity_RESULT_CANCELED 0L
#undef com_example_exercise_MainActivity_RESULT_OK
#define com_example_exercise_MainActivity_RESULT_OK -1L
#undef com_example_exercise_MainActivity_RESULT_FIRST_USER
#define com_example_exercise_MainActivity_RESULT_FIRST_USER 1L
#undef com_example_exercise_MainActivity_DEFAULT_KEYS_DISABLE
#define com_example_exercise_MainActivity_DEFAULT_KEYS_DISABLE 0L
#undef com_example_exercise_MainActivity_DEFAULT_KEYS_DIALER
#define com_example_exercise_MainActivity_DEFAULT_KEYS_DIALER 1L
#undef com_example_exercise_MainActivity_DEFAULT_KEYS_SHORTCUT
#define com_example_exercise_MainActivity_DEFAULT_KEYS_SHORTCUT 2L
#undef com_example_exercise_MainActivity_DEFAULT_KEYS_SEARCH_LOCAL
#define com_example_exercise_MainActivity_DEFAULT_KEYS_SEARCH_LOCAL 3L
#undef com_example_exercise_MainActivity_DEFAULT_KEYS_SEARCH_GLOBAL
#define com_example_exercise_MainActivity_DEFAULT_KEYS_SEARCH_GLOBAL 4L
/*
* Class: com_example_exercise_MainActivity
* Method: test
* Signature: ()Ljava/lang/String;
*/
JNIEXPORT jstring JNICALL Java_com_example_exercise_MainActivity_test
(JNIEnv *, jclass);
/*
* Class: com_example_exercise_MainActivity
* Method: updateFile
* Signature: (Ljava/lang/String;)V
*/
<pre name="code" class="java">JNICALL Java_com_example_exercise_MainActivity_updateFile
(JNIEnv *, jclass, jstring)#ifdef __cplusplus}#endif#endif
JNICALL Java_com_example_exercise_MainActivity_updateFile (JNIEnv *, jclass, jstring)这就是根据我们一开始在mainactivity定义的那个native方法生成的一个方法。有了头文件，我们就可以开始写.c文件了，即实现文件，新建一个文件main.c，然后输入代码如下
#include<stdio.h>
#include<stdlib.h>
JNIEXPORT jstring JNICALL Java_com_example_exercise_MainActivity_test
(JNIEnv * env, jobject obj){
return (*env)->NewStringUTF(env, "Hello world !");
}
LOCAL_PATH :=$(call my-dir) include $(CLEAR_VARS) LOCAL_MODULE := main LOCAL_SRC_FILES := main.c include $(BUILD_SHARED_LIBRARY)
public class MainActivity extends Activity {
public static native String test();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
TextView t = (TextView)findViewById(R.id.jnitextview);
t.setText(test());
}
static {
System.loadLibrary("main");
}
} static {
System.loadLibrary("main");
}main是我们在android.mk中配置的一个名字，现在万事俱备，只差编译生成so文件了，我们打开cmd并且切换到项目的目录下，执行ndk-build，中间是减号，不是下划线，刷新项目就可以看到libs中多了个文件夹和里面的一个libmain.so文件，这时候就可以运行项目了！如果没有意外就会出现helloworld在手机频幕上。LOCAL_PATH :=$(call my-dir) include $(CLEAR_VARS) LOCAL_MODULE := main LOCAL_SRC_FILES := main.c LOCAL_LDLIBS += -llog include $(BUILD_SHARED_LIBRARY)
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原文：http://blog.csdn.net/u013013970/article/details/46981125