首页 > 代码库 > Kivy A to Z -- 如何从python代码中直接访问Android的Service
Kivy A to Z -- 如何从python代码中直接访问Android的Service
在Kivy中，通过pyjnius扩展可以间接调用Java代码，而pyjnius利用的是Java的反射机制。但是在Python对象和Java对象中转来转去总让人感觉到十分别扭。好在android提供了binder这个进程间通信的功能，Java中的Service也是基于Binder的C++代码封装来实现进程间通信的，这也为从Python代码中绕开pyjnius直接访问Java代码提供了可能，既然Java的Service是基于C++的封装来实现的，也同样可以在Python中封装同样的C++代码，这篇文章讲解了如何通过binder在Python代码中直接访问Java的Service，如WifiService。
binder_wrap.h
#ifndef BINDER_WRAP_H
#define BINDER_WRAP_H
#ifdef __cplusplus
extern "C" {
#endif
typedef int (*vector_visitor)(const char16_t* str16,int length,void *data);
typedef int (*fnOnTransact)(uint32_t code,const void *data,void *reply,uint32_t flags,void *userData);
int server_create(const char *name,const char *descriptor,fnOnTransact onTrans,void *data);
void* binder_getbinder(const char *name);
int binder_releasebinder(void* binder);
int binder_listServices(vector_visitor visitor,void *data);
int binder_getInterfaceDescriptor(void *binder,char16_t *descriptor,size_t size);
int binder_transact(void* binder,int code,const void *data,void* reply,int flags);
void* parcel_new();
int parcel_destroy(void* parcel);
int parcel_writeInterfaceToken(void* parcel,const char *interface);
int parcel_writeInt32(void *parcel,int val);
int parcel_writeCString(void *parcel,const char* str);
int parcel_writeString16(void *parcel,const char16_t* str, size_t len);
int parcel_readInt32(void *parcel);
long parcel_readInt64(void *parcel);
int parcel_readString16(void *parcel,char16_t* str, size_t len);
int parcel_readInplace(void *parcel,void* data, int len);
int parcel_readExceptionCode(void *parcel);
int parcel_dataAvail(void *parcel);
#ifdef __cplusplus
}
#endif
#endifbinder_wrap.cpp
#include <sys/types.h>
#include <unistd.h>
#include <grp.h>
#include <binder/IPCThreadState.h>
#include <binder/ProcessState.h>
#include <binder/IServiceManager.h>
#include <utils/Log.h>
#include <binder/Parcel.h>
#include "binder_wrap.h"
using namespace android;
void* binder_getbinder(const char *name)
{
android::sp<android::IServiceManager> sm = android::defaultServiceManager();
sp<IBinder> *binder = new sp<IBinder>();
do {
*binder = sm->getService(android::String16(name));
if (binder != 0)
{
break;
}
usleep(500000); // 0.5 s
} while(true);
return reinterpret_cast<void *>(binder);
}
int binder_releasebinder(void* binder)
{
sp<IBinder> *bp = reinterpret_cast<sp<IBinder> *>(binder);
if(bp == 0)
{
return 0;
}
delete bp;
return 1;
}
//Vector<String16> listServices() = 0;
int binder_listServices(vector_visitor visitor,void *data)
{
android::sp<android::IServiceManager> sm = android::defaultServiceManager();
Vector<String16> list = sm->listServices();
for (int i=0;i<list.size();i++)
{
visitor(list[i].string(),list[i].size(),data);
}
return list.size();
}
int binder_getInterfaceDescriptor(void *binder,char16_t *descriptor,size_t size)
{
sp<IBinder> *bp = reinterpret_cast<sp<IBinder> *>(binder);
if(bp == 0)
{
return 0;
}
if (descriptor == NULL || size <= 0)
{
return 0;
}
String16 des = (*bp)->getInterfaceDescriptor();
if (size > des.size())
{
size = des.size();
}
memcpy(descriptor,des.string(),size*2);
return size;
}
//int binder_transact(void* binder,int code,const Parcel& data,Parcel* reply,int flags = 0)
int binder_transact(void* binder,int code,const void *data,void* reply,int flags)
{
sp<IBinder> *bp = reinterpret_cast<sp<IBinder> *>(binder);
if(bp == 0 || data =http://www.mamicode.com/= 0 || reply == 0)>
正如代码中所示，这里对C++的IBinder和Parcel两个对象进行了封装，而Java的Service的底层实现也正是对这两个类进行封装的结果，具体的可以看
frameworks\base\core\jni\android_util_Binder.cpp
的代码，
再来看下如何在Python中使用这些代码，这里用cython来封装这些C接口：
binder.pyx
cdef extern from "utils/Unicode.h":
ctypedef short char16_t
ctypedef unsigned int uint32_t
cdef extern from "Python.h":
ctypedef short Py_UNICODE
ctypedef size_t Py_ssize_t
object PyString_FromStringAndSize(const char *v, Py_ssize_t len)
int PyString_AsStringAndSize(object obj, char **buffer, Py_ssize_t *length)
object PyUnicode_FromUnicode(const Py_UNICODE *u, Py_ssize_t size)
Py_UNICODE* PyUnicode_AS_UNICODE(object)
Py_ssize_t PyUnicode_GetSize(object)
void Py_INCREF(object)
void Py_DECREF(object)
cdef extern from "binder_wrap.h":
ctypedef int (*vector_visitor)(const char16_t* str16,int length,void *data)
int binder_listServices(vector_visitor visitor,void *data)
ctypedef int (*fnOnTransact)(uint32_t code,const void *data,void *reply,uint32_t flags,void *userData)
int server_create(const char *name,const char *descriptor,fnOnTransact onTrans,void *data)
void* binder_getbinder(const char *name)
int binder_releasebinder(void* binder)
int binder_getInterfaceDescriptor(void *binder,char16_t *descriptor,int size)
int binder_transact(void* binder,int code,const void *data,void* reply,int flags)
void* parcel_new()
int parcel_destroy(void* parcel)
int parcel_writeInterfaceToken(void* parcel,const char *interface)
int parcel_writeInt32(void *parcel,int val)
int parcel_writeCString(void *parcel,const char* str)
int parcel_writeString16(void *parcel,const char16_t* str, size_t len)
int parcel_readInt32(void *parcel)
int parcel_readInt64(void *parcel)
int parcel_readString16(void *parcel,char16_t* str, size_t len)
int parcel_readExceptionCode(void *parcel)
int parcel_readInplace(void *parcel,void* data, int len)
int parcel_dataAvail(void *parcel)
cdef int visitor(const char16_t* str16,int length,void *data):
arr = <object>data
o = PyUnicode_FromUnicode(<Py_UNICODE*>str16,length)
arr.append(o)
def listServices():
arr = []
Py_INCREF(arr)
binder_listServices(visitor,<void *>arr)
Py_DECREF(arr)
return arr
cdef class Binder:
cdef void *ptr
def __cinit__(self,char *name): #, sp[IBinder] service):
self.ptr = binder_getbinder(name)
def __dealloc__(self):
binder_releasebinder(self.ptr)
def getInterfaceDescriptor(self):
cdef char16_t descriptor[256]
cdef int ret
ret = binder_getInterfaceDescriptor(self.ptr,descriptor,sizeof(descriptor))
if not ret:
return None
return PyUnicode_FromUnicode(<Py_UNICODE*>descriptor,ret)
def transact(self,int code,data,reply,int flags):
cdef int dataPtr = data.getNativePtr()
cdef int replyPtr = reply.getNativePtr()
binder_transact(self.ptr,code,<void *>dataPtr,<void*>replyPtr,flags)
return reply
cdef class Parcel:
cdef void *ptr
cdef int nativePtr
def __cinit__(self,unsigned int nativePtr=0): #, sp[IBinder] service):
self.nativePtr = nativePtr
if not nativePtr:
self.ptr = parcel_new()
else:
self.ptr = <void *>nativePtr
def __dealloc__(self):
if not self.nativePtr:
parcel_destroy(self.ptr)
def getNativePtr(self):
return <int>self.ptr
def writeInterfaceToken(self,const char *interface):
return parcel_writeInterfaceToken(<void *>self.ptr,interface)
def writeInt(self,int val):
self.writeInt32(val)
def writeInt32(self,int val):
return parcel_writeInt32(<void *>self.ptr,val)
def writeCString(self,const char* cstr):
return parcel_writeCString(<void *>self.ptr,cstr)
def writeString16(self,ustr):
cdef char16_t *un
cdef int size
if isinstance(ustr,unicode):
un = <char16_t*>PyUnicode_AS_UNICODE(ustr)
size = PyUnicode_GetSize(ustr)
return parcel_writeString16(<void *>self.ptr,un,size)
def readInt32(self):
return parcel_readInt32(self.ptr)
def readInt(self):
return self.readInt32()
def readInt64(self):
return parcel_readInt64(self.ptr)
def readExceptionCode(self):
return parcel_readExceptionCode(self.ptr)
def readString16(self):
cdef char16_t str16[256]
cdef int ret
ret = parcel_readString16(self.ptr,str16,sizeof(str16))
if not ret:
return None
return PyUnicode_FromUnicode(<Py_UNICODE*>str16,ret)
def readByteArray(self):
return self.createByteArray()
def createByteArray(self):
length = self.readInt()
print 'createByteArray:',length
return self.readInplace(length)
# int parcel_readInplace(void *parcel,void* data, size_t len)
def readInplace(self,length):
cdef char arr[512]
ret = parcel_readInplace(self.ptr,arr,length)
if ret == length:
return PyString_FromStringAndSize(arr,length)
else:
return None
# int parcel_dataAvail(void *parcel)
def dataAvail(self):
return parcel_dataAvail(self.ptr)
def createTypedArrayList(self,creator):
N = self.readInt()
if N <= 0:
return None
arr = []
for i in range(N):
if self.readInt() == 0:
continue
else:
result = creator.createFromParcel(self)
arr.append(result)
return arr
@classmethod
def obtain(cls):
return Parcel()
@classmethod
def recycle(cls):
pass
好，再来看看如何来实现访问WifiService的功能：WifiService.py
from binder import Binder,Parcel
WIFI_SERVICE = "wifi";
DESCRIPTOR = "android.net.wifi.IWifiManager";
FIRST_CALL_TRANSACTION = 1
TRANSACTION_getConfiguredNetworks = (FIRST_CALL_TRANSACTION + 0);
TRANSACTION_addOrUpdateNetwork = (FIRST_CALL_TRANSACTION + 1);
TRANSACTION_removeNetwork = (FIRST_CALL_TRANSACTION + 2);
TRANSACTION_enableNetwork = (FIRST_CALL_TRANSACTION + 3);
TRANSACTION_disableNetwork = (FIRST_CALL_TRANSACTION + 4);
TRANSACTION_pingSupplicant = (FIRST_CALL_TRANSACTION + 5);
TRANSACTION_startScan = (FIRST_CALL_TRANSACTION + 6);
TRANSACTION_getScanResults = (FIRST_CALL_TRANSACTION + 7);
TRANSACTION_disconnect = (FIRST_CALL_TRANSACTION + 8);
TRANSACTION_reconnect = (FIRST_CALL_TRANSACTION + 9);
TRANSACTION_reassociate = (FIRST_CALL_TRANSACTION + 10);
TRANSACTION_getConnectionInfo = (FIRST_CALL_TRANSACTION + 11);
TRANSACTION_setWifiEnabled = (FIRST_CALL_TRANSACTION + 12);
TRANSACTION_getWifiEnabledState = (FIRST_CALL_TRANSACTION + 13);
TRANSACTION_setCountryCode = (FIRST_CALL_TRANSACTION + 14);
TRANSACTION_setFrequencyBand = (FIRST_CALL_TRANSACTION + 15);
TRANSACTION_getFrequencyBand = (FIRST_CALL_TRANSACTION + 16);
TRANSACTION_isDualBandSupported = (FIRST_CALL_TRANSACTION + 17);
TRANSACTION_saveConfiguration = (FIRST_CALL_TRANSACTION + 18);
TRANSACTION_getDhcpInfo = (FIRST_CALL_TRANSACTION + 19);
TRANSACTION_acquireWifiLock = (FIRST_CALL_TRANSACTION + 20);
TRANSACTION_updateWifiLockWorkSource = (FIRST_CALL_TRANSACTION + 21);
TRANSACTION_releaseWifiLock = (FIRST_CALL_TRANSACTION + 22);
TRANSACTION_initializeMulticastFiltering = (FIRST_CALL_TRANSACTION + 23);
TRANSACTION_isMulticastEnabled = (FIRST_CALL_TRANSACTION + 24);
TRANSACTION_acquireMulticastLock = (FIRST_CALL_TRANSACTION + 25);
TRANSACTION_releaseMulticastLock = (FIRST_CALL_TRANSACTION + 26);
TRANSACTION_setWifiApEnabled = (FIRST_CALL_TRANSACTION + 27);
TRANSACTION_getWifiApEnabledState = (FIRST_CALL_TRANSACTION + 28);
TRANSACTION_getWifiApConfiguration = (FIRST_CALL_TRANSACTION + 29);
TRANSACTION_setWifiApConfiguration = (FIRST_CALL_TRANSACTION + 30);
TRANSACTION_startWifi = (FIRST_CALL_TRANSACTION + 31);
TRANSACTION_stopWifi = (FIRST_CALL_TRANSACTION + 32);
TRANSACTION_addToBlacklist = (FIRST_CALL_TRANSACTION + 33);
TRANSACTION_clearBlacklist = (FIRST_CALL_TRANSACTION + 34);
TRANSACTION_getWifiServiceMessenger = (FIRST_CALL_TRANSACTION + 35);
TRANSACTION_getWifiStateMachineMessenger = (FIRST_CALL_TRANSACTION + 36);
TRANSACTION_getConfigFile = (FIRST_CALL_TRANSACTION + 37);
TRANSACTION_captivePortalCheckComplete = (FIRST_CALL_TRANSACTION + 38);
mRemote = Binder(WIFI_SERVICE)
def transact(TRANSACTION):
_data = http://www.mamicode.com/Parcel()>
目前并没有实现所有的WifiService的功能，但是像startScan，getScanResults,setWifiEnabled,getWifiEnabledState,getDhcpInfo,setWifiApEnabled这些主要的接口已经实现了，其它接口没有实现并非是因为不能实现，而是比较繁琐，暂时未实现而己，后面会不断的完善。
再来看下测试代码：
test.py
import WifiService
WifiService.setWifiEnabled(True)
WifiService.startScan(True)
print WifiService.pingSupplicant()
print WifiService.getConfigFile()
for i in range(10):
time.sleep(1.0)
result = WifiService.getScanResults()
if result:
print result
break
执行后将会打印出搜索到的Wifi信息。
另外就是代码的编译问题了。代码必须在android的源代码下进行编译。我试过在ndk上进行编译，经过一番努力，通过链接事先编译好的C++ binder库，也成功编译通过，但是程序不能正常运行，这应该是预先编译出来的库和ndk的库存在兼容性问题造成的，或许通过在ndk上编译binder库可以避免这个问题，但是目前还没有作过尝试。 但是编译出来的代码应该可以运行在各个不同的版本，我在4.0和4.2版本的设备上作了简单的测试，事实证明在4.2上编译的代码可以在4.0上运行，但是考虑到android的诸多版本，各个版本多多少少有些兼容性问题，更详细的还必须比较各个版本的binder代码，并通过测试才能得到结果。
我已经在github上创建了一个叫pydroid的项目，该项目的目的是希望在android平台上充分发挥python的开发优势，结合android上的python图形库kivy，希望能让在android平台上开发应用程序变得更加简单，更加有趣。当然，这个项目能走多远还不得而知，
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