linux android ndk

Android调用so库, so库是c语言编写, 在linux 64位系统+ndk(32位)生成 lib*.so (32位)

1. 所需软件环境：

1）so库开发环境

操作系统： Redhat Server 6.3 x86_64

编译软件：Code::Blocks

Android native开发库：android-ndk-r9c-linux-x86.tar.bz2

[xxx@www ~]$ uname -a

Linux www.teleframe.cn 2.6.32-279.el6.x86_64 #1 SMP Wed Jun 13 18:24:36 EDT 2012 x86_64 x86_64 x86_64 GNU/Linux

[xxx@www ~]$ cat /proc/version

Linux version 2.6.32-279.el6.x86_64 (mockbuild@x86-008.build.bos.redhat.com) (gcc version 4.4.6 20120305 (Red Hat 4.4.6-4) (GCC) ) #1 SMP Wed Jun 13 18:24:36 EDT 2012

[xxx@www ~]$ cat /etc/issue

Red Hat Enterprise Linux Server release 6.3 (Santiago)

Kernel \r on an \m

2） Android客户端开发

操作系统：Windows 7 x86

测试环境： Android手机（系统4.0及以上）

开发工具和SDK包： adt-bundle-windows-x86-20131030.zip(里面含有Eclipse)

本文所需软件如下：

android-ndk-r9c-linux-x86.tar.bz2 http://developer.android.com/intl/zh-cn/tools/sdk/ndk/index.html
adt-bundle-windows-x86-20131030.zip http://developer.android.com/intl/zh-cn/sdk/index.html
Code::Blocks http://www.codeblocks.org/downloads/binaries

2. 环境搭建

1）Code::Blocks环境搭建

首先安装Code::Blocks, 然后解压 android-ndk-r9c-linux-x86.tar.bz2 , 如解压到桌面 /home/UserName/Desktop/android-ndk-r9c/
然后启动Code::Blocks, 进行系统环境配置

1.1) 配置全局环境

S1: 打开 Settings-> Compiler and debugger...

S2: 选择编译器Selected complier -> GNU ARM GCC Complier，或自己新建一个

S3: 选择 Toolchain executables

S4: 设置android-ndk路径( Complier's installation directory ) ，如 /home/xxx/Desktop/android-ndk-r9c/toolchains/arm-linux-androideabi-4.6/prebuilt/linux-x86

S5: 设置Program Files各个编译程序

C complier: arm-linux-androideabi-gcc

C++ compiler: arm-linux-androideabi-g++

Linker for dynamic libs: arm-linux-androideabi-g++

Linker for static libs: arm-linux-androideabi-ar

Debugger: arm-linux-androideabi-gdb

Resource compiler:

S6: 设置Additional Paths, 增加(Add) : /home/xxx/Desktop/android-ndk-r9c/toolchains/arm-linux-androideabi-4.6/prebuilt/linux-x86/arm-linux-androideabi/bin

S7: 设置 Search directories -> Compiler, 增加(Add) : /home/xxx/Desktop/android-ndk-r9c/toolchains/arm-linux-androideabi-4.6/prebuilt/linux-x86/include

S8: 设置 Search directories -> Linker,

/home/xxx/Desktop/android-ndk-r9c/toolchains/arm-linux-androideabi-4.6/prebuilt/linux-x86/lib
/home/xxx/Desktop/android-ndk-r9c/toolchains/arm-linux-androideabi-4.6/prebuilt/linux-x86/lib/gcc/arm-linux-androideabi/4.6
/home/xxx/Desktop/android-ndk-r9c/toolchains/arm-linux-androideabi-4.6/prebuilt/linux-x86/lib/gcc/arm-linux-androideabi/4.6/armv7-a

S9: 设置完成，点击确定

1.2) 配置项目的环境

S1: 右击项目，选择Build options, Selected Complier选择刚才设置的那个 GUN ARM GCC Compiler

S2: Compler settings -> Other options , 写入 -fPIC

S3: 设置 Search directories -> Linker, Add :

/home/xxx/Desktop/android-ndk-r9c/platforms/android-14/arch-arm/usr/lib

S4: Search directories->Complier , Add

/home/xxx/Desktop/android-ndk-r9c/platforms/android-14/arch-arm/usr/include

2）Android 开发环境搭建

直接解压 adt-bundle-windows-x86-20131030.zip ，如解压到 E:\Program Files\adt\adt-bundle-windows-x86-20131030

就可以看到里面以及放好了eclipse, 此处的eclipse默认已经配置好了 adt, 启动 eclipse.exe 配置android虚拟机

菜单 Window -> Android Virtual Device Manager 管理虚拟机， Android SDK Manager 可以更新 SDK，由于此adt所带android系统是4.4, 建议再更新 4.0.3 (

手动更新详见：手动下载Android开发SDK
sdk:platform -> https://dl-ssl.google.com/android/repository/android-14_r03.zip
sdk:system-image -> https://dl-ssl.google.com/android/repository/sysimg_armv7a-14_r02.zip
)

如下图所示

新建一个虚拟机

3. SO库编写

3.1）生成头文件

打开adt-bundle-windows里面的Eclipse

新建Android项目JniTestAndroid ，建立包 com.lpr，建类 JniTestAndroid

JniTestAndroid.java

package com.lpr;
class JniTestAndroid {
public native byte[] recognition(byte arr[]);
static {
System.loadLibrary("AndroidCallsoDemo");//Load AndroidCallsoDemo.so produce by code::blocks
// System.out.println(System.getProperty("java.library.path"));
// System.setProperty("java.library.path", ".");
}
}

用 Javac 编译成 class文件

>cd E:\JniTestAndroid

>javac com/lpr/JniTestAndroid.java

>javah com.lpr.JniTestAndroid

现在生成了 com_lpr_JniTestAndroid.h

/* DO NOT EDIT THIS FILE - it is machine generated */
#include <jni.h>
/* Header for class com_lpr_JniTestAndroid */
#ifndef _Included_com_lpr_JniTestAndroid
#define _Included_com_lpr_JniTestAndroid
#ifdef __cplusplus
extern "C" {
#endif
/*
* Class: com_lpr_JniTestAndroid
* Method: recognition
* Signature: ([S)[B
*/
JNIEXPORT jbyteArray JNICALL Java_com_lpr_JniTestAndroid_recognition
(JNIEnv *, jobject, jbyteArray);
#ifdef __cplusplus
}
#endif
#endif

现在将com_lpr_JniTestAndroid.h拷贝到 Redhat 下面

并将 $java_home/include/jni.h 和 ./linux/jni_md.h 拷贝到 redhat 下面

在此特给出 jni_md.h 源码

#ifndef _JAVASOFT_JNI_MD_H_
#define _JAVASOFT_JNI_MD_H_
#define JNIEXPORT
#define JNIIMPORT
#define JNICALL
typedef long jint;
typedef __int64 jlong;
typedef signed char jbyte;
#endif /* !_JAVASOFT_JNI_MD_H_ */

3.2）编写SO库

打开Code::Block新建(动态库)项目 AndroidCallsoDemo，设置项目属性参考上面的【 1.2 配置项目的环境】

添加 com_lpr_JniTestAndroid.h, jni.h, jni_md.h 到项目（不添加也可以，只要放到项目的更目录即可）

main.cpp

#include "stdio.h"
#include "com_lpr_JniTestAndroid.h"
JNIEXPORT jbyteArray JNICALL Java_com_lpr_JniTestAndroid_recognition
(JNIEnv *jnienv, jobject jobj, jbyteArray byteArray)
{
/* short* iArray ; //=new short[maxSize];
jboolean jbool = true;
//转换数组
iArray = jnienv->GetShortArrayElements(shortArray, &jbool);
//...
//
jnienv->ReleaseShortArrayElements(shortArray,iArray,0);
// do something with iArray ...
// carnumber;
*/
char carnumber[64]= {"你输入的是:"};
jbyteArray returnLPRArray = jnienv->NewByteArray( 64 );
jbyte *retbytes = jnienv->GetByteArrayElements( returnLPRArray, 0);
jbyte *bytes2 = jnienv->GetByteArrayElements(byteArray, 0);
sprintf(carnumber, "%s %s",carnumber, bytes2);
int nLPRLen = strlen(carnumber);
//返回值最好是 byte,以免utf8造成汉字的影响
for ( int i = 0; i < nLPRLen; i++ )
{
retbytes[ i ] = carnumber[ i ];
}
jnienv->SetByteArrayRegion(returnLPRArray, 0, nLPRLen, retbytes );
return returnLPRArray ;
}

几点注意：

1. 如果传入参数或传出参数有汉字或比较复杂的结构，建议都化为 jbyteArray, 特别是有关的汉字问题

4. Android编写

建立android项目 JniTestAndroid

activity_karl.xml //

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#F5F6F2"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context=".KarlActivity" >
<TextView
android:id="@+id/textView"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="center_horizontal"
android:text="result"
android:textSize="20sp" />
<Button
android:id="@+id/button1"
android:layout_width="match_parent"
android:layout_height="40dp"
android:layout_below="@+id/textView"
android:gravity="center_horizontal"
android:text="Button" />
</RelativeLayout>

拷贝 com.lpr.JniTestAndroid 到项目 src 下面

karlActivity.java

package com.karl.jnitestandroid;
import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;
import com.lpr.JniTestAndroid;
public class KarlActivity extends Activity {
private JniTestAndroid jni = new JniTestAndroid();
private Button bt;
private TextView textView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_karl);
textView = (TextView)findViewById(R.id.textView);
bt = (Button) findViewById(R.id.button1);
bt.setOnClickListener(new OnClickListener(){
@Override
public void onClick(View arg0) {
String str="中国北京123ABC";
byte data[] = jni.recognition(str.getBytes());
String text = new String(data); //new String(data, "GB2312");
textView.setText(text);
}
});
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.karl, menu);
return true;
}
}

运行结果

5. 常见错误

5.1) ld: error: cannot open crtbegin_so.o: No such file or directory

arm-linux-androideabi-g++ -Wall -fexceptions -O2 -fPIC -I../android-ndk-r9c/platforms/android-14/arch-arm/usr/include -c main.cpp -o obj/Release/main.o
/home/haifeng/android/android-ndk-r9c/toolchains/arm-linux-androideabi-4.6/prebuilt/linux-x86/bin/../lib/gcc/arm-linux-androideabi/4.6/../../../../arm-linux-androideabi/bin/as: /lib/libz.so.1: no version information available (required by /home/haifeng/android/android-ndk-r9c/toolchains/arm-linux-androideabi-4.6/prebuilt/linux-x86/bin/../lib/gcc/arm-linux-androideabi/4.6/../../../../arm-linux-androideabi/bin/as)
arm-linux-androideabi-g++ -shared -L../android-ndk-r9c/platforms/android-14/arch-arm/usr/lib -L/home/haifeng/android/android-ndk-r9c/platforms/android-14/arch-arm/usr/lib obj/Release/main.o -o bin/Release/libAndroidCallsoDemo.so -s
/home/haifeng/android/android-ndk-r9c/toolchains/arm-linux-androideabi-4.6/prebuilt/linux-x86/bin/../lib/gcc/arm-linux-androideabi/4.6/../../../../arm-linux-androideabi/bin/ld: error: cannot open crtbegin_so.o: No such file or directory
/home/haifeng/android/android-ndk-r9c/toolchains/arm-linux-androideabi-4.6/prebuilt/linux-x86/bin/../lib/gcc/arm-linux-androideabi/4.6/../../../../arm-linux-androideabi/bin/ld: error: cannot open crtend_so.o: No such file or directory
collect2: ld returned 1 exit status

原因是ld找不到 crtbegin_so.o 和 crteng_so.o, 解决方法是，在项目源码下面建立软连接

cd /home/xxx/android/AndroidCallsoDemo/

ln -s /home/xxx/android/android-ndk-r9c/platforms/android-14/arch-arm/usr/lib/crtend_so.o ./

ln -s /home/xxx/android/android-ndk-r9c/platforms/android-14/arch-arm/usr/lib/crtbegin_so.o ./

5.2) 查看SO库的依赖库

查看PC linux 平台是用 ldd, 查看嵌入式的用 arm-linx-*-readelf

/home/xxx/Desktop/android-ndk-r9c/toolchains/arm-linux-androideabi-4.6/prebuilt/linux-x86/bin/arm-linux-androideabi-readelf -a AndroidCallsoDemo.so

或者

/home/xxx/Desktop/android-ndk-r9c/toolchains/arm-linux-androideabi-4.6/prebuilt/linux-x86/bin/arm-linux-androideabi-readelf -a AndroidCallsoDemo.so | grep "Shared"

5.3) 使用STL
直接使用STL或用Opencv间接调用STL, 提示找不到 #include <algorithm> 等, 在工程的 Build Options -> Search directories -> Complier添加如下包含目录即可

/home/xxx/Desktop/android-ndk-r9c/sources/cxx-stl/gnu-libstdc++/4.6/include

/home/xxx/Desktop/android-ndk-r9c/sources/cxx-stl/gnu-libstdc++/4.6/libs/armeabi-v7a/include