android ndk 入门实践

android简单实现调用c语言代码

ndk等环境配置略过

Activity实现如下

package com.xl.qiu;

import android.app.Activity;

import android.os.Bundle;

import android.view.View;

import android.view.View.OnClickListener;

import android.widget.Button;

import android.widget.TextView;

public class MyTwoLibsActivity extends Activity implements OnClickListener{

/** Called when the activity is first created. */

Button add;

Button minus;

Button ppi;

Button mmi;

TextView text;

@Override

public void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.main);

add = (Button)findViewById(R.id.addition);

minus = (Button)findViewById(R.id.subtraction);

ppi = (Button)findViewById(R.id.ppi);

mmi = (Button)findViewById(R.id.mmi);

text = (TextView)findViewById(R.id.text);

text.setText("0");

add.setOnClickListener(this);

minus.setOnClickListener(this);

ppi.setOnClickListener(this);

mmi.setOnClickListener(this);

}

public void onClick(View v) {

// TODO Auto-generated method stub

switch(v.getId())

{

case R.id.addition:

text.setText(""+add(23, 11));

break;

case R.id.subtraction:

text.setText(""+minus(23, 11));

break;

case R.id.ppi:

text.setText(""+ppi(Integer.parseInt(text.getText().toString())));

break;

case R.id.mmi:

text.setText(""+mm_i(Integer.parseInt(text.getText().toString())));

break;

}

}

public native int add(int x, int y);

public native int minus(int x, int y);

public native int ppi(int x);

public native int mm_i(int x);

static {

System.loadLibrary("mytwolibsecond");

}

}

4个native函数add`minus`ppi`mm_i分别实现整数相加｀相减｀自加++i｀自减--i;

项目build过后，可以见到成功生成了com.xl.qiu.MyTwoLibsActivity.class

Next：项目目录下建立jni文件夹...此时目录形如 src/ gen/ jni/ res/ ......

shell执行 javah -classpath bin -d jni com.xl.qiu.MyTwoLibsActivity

成功执行后在jni目录下生成了com_xl_qiu_MyTwoLibsActivity.h

内容如下：

/* DO NOT EDIT THIS FILE - it is machine generated */

#include <jni.h>

/* Header for class com_xl_qiu_MyTwoLibsActivity */

#ifndef _Included_com_xl_qiu_MyTwoLibsActivity

#define _Included_com_xl_qiu_MyTwoLibsActivity

#ifdef __cplusplus

extern "C" {

#endif

/*

* Class: com_xl_qiu_MyTwoLibsActivity

* Method: add

* Signature: (II)I

*/

JNIEXPORT jint JNICALL Java_com_xl_qiu_MyTwoLibsActivity_add

(JNIEnv *, jobject, jint, jint);

/*

* Class: com_xl_qiu_MyTwoLibsActivity

* Method: minus

* Signature: (II)I

*/

JNIEXPORT jint JNICALL Java_com_xl_qiu_MyTwoLibsActivity_minus

(JNIEnv *, jobject, jint, jint);

/*

* Class: com_xl_qiu_MyTwoLibsActivity

* Method: ppi

* Signature: (I)I

*/

JNIEXPORT jint JNICALL Java_com_xl_qiu_MyTwoLibsActivity_ppi

(JNIEnv *, jobject, jint);

/*

* Class: com_xl_qiu_MyTwoLibsActivity

* Method: mm_i

* Signature: (I)I

*/

JNIEXPORT jint JNICALL Java_com_xl_qiu_MyTwoLibsActivity_mm_1i

(JNIEnv *, jobject, jint);

#ifdef __cplusplus

}

#endif

#endif

把已存在的c代码及其头文件代码也放入jni目录中

purec.h代码如下：

#ifndef PUREC_H

#define PRUEC_H

extern int add(int x, int y);

extern int minus(int x, int y);

extern int ppi(int x);

extern int mmi(int x);

#endif

purec.c代码如下：

#include "purec.h"

int add(int x, int y)

{

return x + y;

}

int minus(int x, int y)

{

return x - y;

}

int ppi(int x)

{

return ++x;

}

int mmi(int x)

{

return --x;

}

编写com_xl_qiu_MyTwoLibsActivity.c代码如下：

#include <jni.h>

#include "com_xl_qiu_MyTwoLibsActivity.h"

#include "purec.h"

jint Java_com_xl_qiu_MyTwoLibsActivity_add(

JNIEnv *env,

jobject this,

jint x,

jint y

)

{

return add(x, y);

}

jint Java_com_xl_qiu_MyTwoLibsActivity_minus(

JNIEnv *env,

jobject this,

jint x,

jint y

)

{

return minus(x, y);

}

jint Java_com_xl_qiu_MyTwoLibsActivity_ppi(

JNIEnv *env,

jobject this,

jint x

)

{

return ppi(x);

}

jint Java_com_xl_qiu_MyTwoLibsActivity_mm_1i(

JNIEnv *env,

jobject this,

jint x

)

{

return mmi(x);

}

jni源文件完毕...下面编写Android.mk同样放在jni目录下

LOCAL_PATH:=$(call my-dir)

include $(CLEAR_VARS)

LOCAL_MODULE := libmytwolibfirst

LOCAL_SRC_FILES := purec.c

include $(BUILD_STATIC_LIBRARY)

include $(CLEAR_VARS)

LOCAL_MODULE := libmytwolibsecond

LOCAL_SRC_FILES := com_xl_qiu_MyTwoLibsActivity.c

LOCAL_STATIC_LIBRARIES :=libmytwolibfirst

include $(BUILD_SHARED_LIBRARY)

mk文件写完毕...

执行$NDK/ndk-build（$NDK已经设置的情况下）

可以看到.so类库已经生成，可以Run Android Application了

注意：本地方法自加（ppi）自减(mm_i)命名不一样（mm_i多了一个_）

在生成.h文件的时候请注意区别