android 实现framework和底层C/C++通讯
最近接到一个需求，要在framework中添加一些上层接口给客户调用，然后在framework中调用C中的代码实现和硬件一些数据交互。framework和C交互肯定想到的使用jni，但是和硬件交互的时候需要执行一些shell命令，必须要root权限才能执行成功，如果在framework中使用jni，显然无法达到我们想要的效果，后来就换了种方式实现，使用localscoket来实现，在系统添加一个服务，然后在init.rc中配置root权限，最终在这个服务中实现C代码。代码如下：
framework为服务端：
private class ServerSocket implements Runnable {
private boolean keepRunning = true;
private LocalServerSocket serverSocket;
private String socketName;
InputStream inputStream = null;
public ServerSocket(String socketName) {
this.socketName = socketName;//这个名字必须和底层socket的名字一样
Log.e("HarryCan", "socketName : " + socketName );
}
public void stopScoket() {
keepRunning = false;
if (serverSocket != null) {
try {
serverSocket.close();
serverSocket = null;
} catch (IOException e) {
e.printStackTrace();
}
}
}
@Override
public void run() {
try {
serverSocket = new LocalServerSocket(socketName);
} catch (IOException e) {
e.printStackTrace();
keepRunning = false;
}
Log.e(TAG, socketName + " wait for new client coming !");
try {
LocalSocket interactClientSocket = serverSocket.accept();
if (keepRunning) {
Log.e(TAG, socketName + " new client coming !");
try {
inputStream = interactClientSocket.getInputStream();
byte[] buf = new byte[1024];
int readBytes = -1;
while ((readBytes = inputStream.read(buf)) != -1 && keepRunning) {
// buff is the result
}
} catch (IOException e) {
e.printStackTrace();
} finally {
if (inputStream != null) {
try {
inputStream.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
} catch (IOException e) {
e.printStackTrace();
keepRunning = false;
}
if (inputStream != null) {
try {
inputStream.close();
} catch (IOException e) {
e.printStackTrace();
}
}
Log.e(TAG, socketName + " finish running !");
}
}开启线程既可以开启服务端。
系统服务客户端代码：
导入头文件:#include
#include
//socketName必须和服务端相同，获取到socket句柄fd
int fd = socket_local_client(socketName, ANDROID_SOCKET_NAMESPACE_ABSTRACT, SOCK_STREAM);因为要不断的把从硬件采集到的数据返回的上层api，所以这里开了一个线程来把数据写入到socket，然后在framework中接收：
Param *param = new Param();//结构体传参
param->s = s;
param->frame = frame;
pthread_t thread_id;
pthread_create( &thread_id, NULL, &threadFunc, param);
void *threadFunc(void *data) {
ALOGE(" threadFunc enter in");
int nbytes;
Param *param = (Param *)data;
int s = param->s;
struct can_frame frame = param->frame;
char dest[20];
while(openCanFlag) {
nbytes = read(s, &frame, sizeof(frame));//循环获取数据，这里通过一个socekt从硬件获取，不关注
//对数据做转化
if (nbytes > 0) {
char a,b,c,d;
a=(char)(frame.can_id&0xff);
b=(char)((frame.can_id&0xff00)>>8);
c=(char)((frame.can_id&0xff0000)>>16);
d=(char)((frame.can_id&0xff000000)>>24);
frame.can_id=(a<<24)|(b<<16)|(c<<8)|d;
memcpy(&dest[0], (char*)&frame.can_id, sizeof(__u32));
for(int i = 0; i < frame.can_dlc; i++){
dest[i+4] = frame.data[i];
}
//将转化后的数据写入到socekt，并在framework接收
write(fd, dest, sizeof(dest));
}
}
ALOGE("threadFunc startCanSocket loop end");
close(s);
pthread_exit(0);
return NULL;
}
然后还有一种，framework做客户端，C代码做服务端也一并实现：
framework做客户端：
private OutputStream mOutputStream;
private LocalSocket socket;
private void listenToSocket(String socketName) throws IOException {
try {
socket = new LocalSocket();
socket.connect(new LocalSocketAddress(socketName));
mOutputStream = socket1.getOutputStream();
Log.e(TAG, socketName + " connect to server ");
} catch (IOException ex) {
Log.e(TAG, socketName + " listenToSocket error : " + ex.toString());
}
}
private void closeSocket() throws IOException {
if (mOutputStream1!= null) {
try {
mOutputStream.close();
} catch (IOException e) {
Log.e(TAG, " Failed closing output stream write_uart1_rt_socket");
}
mOutputStream = null;
}
try {
if (socket != null) {
socket.close();
}
} catch (IOException ex) {
Log.e(TAG, " Failed closing socket : write_uart1_rt_socket");
}
}
private void initSocketClient(final String socketName) {
new Thread(new Runnable() {
@Override
public void run() {
// TODO Auto-generated method stub
try {
listenToSocket(socketName);
} catch (Exception e) {
Log.e(TAG, socketName + " Error listenToSocket : " + e.toString());
}
}
}).start ();
}//发送数据到服务端
public void writeGPSUart1Data(byte[] data) throws Exception {
mOutputStream.write(data);
mOutputStream.flush();
Log.e(TAG, "write flush data end ");
}
系统服务中C代码实现服务端：
//获取socket句柄，socketName必须和客户端保持一致
int uart2_fd = socket_local_server(socketName, ANDROID_SOCKET_NAMESPACE_ABSTRACT, SOCK_STREAM);
pthread_t thread_id_2;
pthread_create( &thread_id_2, NULL, &threadUart2Func, NULL);//开启线程接受数据
void *thread2Func(void *data) {
ALOGE("threadUart2Func enter in");
char buf2[512] = {0};
int socketID = accept(uart2_fd,NULL,NULL);//等待客户端连接
int ret;
while((ret = read(socketID,buf2,sizeof(buf2))) >=0){//循环读取数据
int result = uart2_write(buf2,ret);
if(isInitGPSModule == 0){
ALOGE("thread2Func exit thread\n");
close(uart2_fd);
pthread_exit(0);
}
}
ALOGE("thread2Func loop end\n");
close(uart2_fd);
pthread_exit(0);
return ((void *)data);
}
服务端必须在客户端连接之前先初始化，否则客户端无法连接。
在工作中遇到的问题做下简单记录，如果有错误，欢迎大家指正，谢谢！