Binder使用示例

BInder方面的资料虽然感觉看的比较多，但是真正用的时候才发现有很多地方模棱两棵的，所以，打算用一个实例再来巩固一下binder的使用方法

首先看下目录结构：

 leaves@leaves-desktop:~/android/android2/android/frameworks/tv_print/services$ ls T*
 TestBinderClient:
 Android.mk  ITestBinderService.cpp

 TestBinderServer:
 Android.mk  ITestBinderService.h  main_testBinder.cpp  testBinder.cpp  TestBinderService.cpp  TestBinderService.h
 leaves@leaves-desktop:~/android/android2/android/frameworks/tv_print/services$

TestBinderClient下面是Binder的客户端，TestBinderServer是binder的服务端

我们先来看下biner服务端代码

1、ITestBinderService.h

 #ifndef ANDROID_ITESTBINDERSERVICE_H_
 #define ANDROID_ITESTBINDERSERVICE_H_

 #include <utils/RefBase.h>
 #include <binder/IInterface.h>
 #include <binder/Parcel.h>


 namespace android {

 class Parcel;

 class ITestBinderService: public IInterface {
 public:
     DECLARE_META_INTERFACE(TestBinderService);

     virtual int add(int a, int b) = 0;
 };

 class BnTestBinderService: public BnInterface<ITestBinderService> {
 public:
     virtual status_t onTransact(uint32_t code, const Parcel& data,
             Parcel* reply, uint32_t flags = 0);
 };

 }

 #endif /* ANDROID_ITESTBINDERSERVICE_H_ */

这里主要是定义了两个类ITestBinderService 和 BnTestBinderService，ITestBinderService 是TestBinderService 的基类，

这里主要是DECLARE_META_INTERFACE 这个宏，定义在frameworks\base\include\binder\IInterface.h文件中

 #define DECLARE_META_INTERFACE(INTERFACE)                               \
     static const android::String16 descriptor;                          \
     static android::sp<I##INTERFACE> asInterface(                       \
             const android::sp<android::IBinder>& obj);                  \
     virtual const android::String16& getInterfaceDescriptor() const;    \
     I##INTERFACE();                                                     \
     virtual ~I##INTERFACE();

把TestBinderService代入进去

 #define DECLARE_META_INTERFACE(TestBinderService)                               \
     static const android::String16 descriptor;                          \
     static android::sp<I##TestBinderService> asInterface(                       \
             const android::sp<android::IBinder>& obj);                  \
     virtual const android::String16& getInterfaceDescriptor() const;    \
     I##TestBinderService();                                                     \
     virtual ~I##TestBinderService();

其中封装了实现binder所需要的一些类成员变量和成员函数，通过这些成员函数可以为一个binder实现创建proxy
2、TestBinderService.h

 #ifndef ANDROID_TESTBINDERSERVICE_H_
 #define ANDROID_TESTBINDERSERVICE_H_

 #include <utils/KeyedVector.h>
 #include "ITestBinderService.h"

 namespace android {

 class TestBinderService: public BnTestBinderService {
 public:
     static void instantiate();
     int add(int a,int b);
 private:
     TestBinderService();
     virtual ~TestBinderService();
 };

 }

 #endif /* ANDROID_TESTBINDERSERVICE_H_ */

这个文件比较简单，主要就是定义了一个类TestBinderService，继承于前面 的BnTestBinderService，并定义了一个方法add函数和instantiate

3、TestBinderService.cpp

 #define LOG_TAG "TestBinderService"

 #include <utils/Log.h>
 #include <binder/IServiceManager.h>
 #include <binder/IPCThreadState.h>

 #include "TestBinderService.h"
 static int debug_flag = 1;
 namespace android {

 void TestBinderService::instantiate() {
     LOGI("Enter TestBinderService::instantiate");
     status_t st = defaultServiceManager()->addService(
             String16("my.test.binder"), new TestBinderService());
     LOGD("ServiceManager addService ret=%d", st);
     LOGD("instantiate> end");
 }

 TestBinderService::TestBinderService() {
     LOGD(" TestBinderServicet");
 }

 TestBinderService::~TestBinderService() {
     LOGD("TestBinderService destroyed,never destroy normally");
 }

 int TestBinderService::add(int a,int b) {

     LOGI("TestBinderService::add a = %d, b = %d.", a , b);
     return a+b;
 }

 }

在instantiate函数中，将TestBinderService注册到系统的binder service列表中，这样以后就可以使用这个service提供的方法

该service提供了一个add 方法，返回两个数的和

再来看下clinet端 的代码

1、ITestBinderService.cpp

 #define LOG_TAG "ITeeveePlayerService"

 #include <utils/Log.h>

 #include "../TestBinderServer/ITestBinderService.h"

 namespace android {

 enum {
     TEST_ADD = IBinder::FIRST_CALL_TRANSACTION,
 };

 class BpTestBinderService: public BpInterface<ITestBinderService> {
 public:
     BpTestBinderService(const sp<IBinder>& impl) :
         BpInterface<ITestBinderService> (impl) {
     }

     int add(int a, int b) {

         Parcel data, reply;
         LOGI("Enter BpTestBinderService add,a = %d , b = %d", a, b);
         data.writeInterfaceToken(ITestBinderService::getInterfaceDescriptor());
         data.writeInt32(a);
         data.writeInt32(b);
         remote()->transact(TEST_ADD, data, &reply);
         int sum = reply.readInt32();
         LOGI("BpTestBinderService sum = %d", sum);
         return sum;
     }
 };

 IMPLEMENT_META_INTERFACE(TestBinderService, "android.test.ITestBinderService");

 // ----------------------------------------------------------------------

 status_t BnTestBinderService::onTransact(uint32_t code, const Parcel& data,
         Parcel* reply, uint32_t flags) {
     switch (code) {
     case TEST_ADD: {

         CHECK_INTERFACE(ITestBinderService, data, reply);
         int a = data.readInt32();
         int b = data.readInt32();
         LOGI("Enter BnTestBinderService add,a = %d , b = %d", a, b);
         int sum = 0;
         sum  = add(a, b);
         LOGI("BnTestBinderService sum = %d", sum);
          reply->writeInt32(sum);
         return sum;
     }
     default:
         return BBinder::onTransact(code, data, reply, flags);
     }
 }

 }

定义了一个类BpTestBinderService，提供add方法，该方法通过调用远端的binder service提供的服务返回两个数的和

重载了BnTestBinderService的onTransact方法，使其在TEST_ADD时调用add方法

这个文件里面也使用了一个宏IMPLEMENT_META_INTERFACE，也是定义在frameworks\base\include\binder\IInterface.h文件中

 #define IMPLEMENT_META_INTERFACE(INTERFACE, NAME)                       \
     const android::String16 I##INTERFACE::descriptor(NAME);             \
     const android::String16&                                            \
             I##INTERFACE::getInterfaceDescriptor() const {              \
         return I##INTERFACE::descriptor;                                \
     }                                                                   \
     android::sp<I##INTERFACE> I##INTERFACE::asInterface(                \
             const android::sp<android::IBinder>& obj)                   \
     {                                                                   \
         android::sp<I##INTERFACE> intr;                                 \
         if (obj != NULL) {                                              \
             intr = static_cast<I##INTERFACE*>(                          \
                 obj->queryLocalInterface(                               \
                         I##INTERFACE::descriptor).get());               \
             if (intr == NULL) {                                         \
                 intr = new Bp##INTERFACE(obj);                          \
             }                                                           \
         }                                                               \
         return intr;                                                    \
     }                                                                   \
     I##INTERFACE::I##INTERFACE() { }                                    \
     I##INTERFACE::~I##INTERFACE() { }

代入展开后：

 #define IMPLEMENT_META_INTERFACE(TestBinderService, "android.test.ITestBinderService")                       \
     const android::String16 ITestBinderService::descriptor("android.test.ITestBinderService");             \
     const android::String16&                                            \
             ITestBinderService::getInterfaceDescriptor() const {              \
         return ITestBinderService::descriptor;                                \
     }                                                                   \
     android::sp<ITestBinderService> ITestBinderService::asInterface(                \
             const android::sp<android::IBinder>& obj)                   \
     {                                                                   \
         android::sp<ITestBinderService> intr;                                 \
         if (obj != NULL) {                                              \
             intr = static_cast<ITestBinderService*>(                          \
                 obj->queryLocalInterface(                               \
                         ITestBinderService::descriptor).get());               \
             if (intr == NULL) {                                         \
                 intr = new BpTestBinderService(obj);                          \
             }                                                           \
         }                                                               \
         return intr;                                                    \
     }                                                                   \
     ITestBinderService::ITestBinderService() { }                                    \
     ITestBinderService::~ITestBinderService() { }

这里重点看 一下asInterface函数，IBinder::queryLocalInterface函数位于framework/base/libs/binder/Binder.cpp文件中

 sp<IInterface>  IBinder::queryLocalInterface(const String16& descriptor)
 {
     return NULL;
 }

由此可见，最终会调用下面语句：
 intr = new BpTestBinderService(obj)

这样，server和client端的binder代码主写好了，接着就需要把binder service加入到binder中

这里有两种方法：

1、在system_init.cpp中添加

TestBinderService::instantiate();

如果是在这里加的话可以去掉TestBinderService中实现的instantiate方法，同时将TestBinderService继承自BinderService，因为在BinderService实现了这一方法，同时将其添加到binder service

2、以单独的程序启动

main_testBinder.cpp

 #include <binder/IPCThreadState.h>
 #include <binder/ProcessState.h>
 #include <binder/IServiceManager.h>
 #include <utils/Log.h>


 #include "TestBinderService.h"

 using namespace android;

 int main(int argc, char** argv)
  {

     sp<ProcessState> proc(ProcessState::self());
     sp<IServiceManager> sm = defaultServiceManager();
     LOGI("TestBinderService before");
     TestBinderService::instantiate();
     LOGI("TestBinderService End");
     ProcessState::self()->startThreadPool();
     IPCThreadState::self()->joinThreadPool();
     return 0;

 }

这里调用的是TestBinderService自己的instantiate来添加的

再来看下测试case,testBinder.cpp

 #define LOG_TAG "TestBinserService"

 #include <utils/Log.h>
 #include <nativehelper/jni.h>
 #include <nativehelper/JNIHelp.h>
 #include <android_runtime/AndroidRuntime.h>
 #include <binder/IServiceManager.h>
 #include "../TestBinderServer/ITestBinderService.h"


 #include "TestBinderService.h"

 using namespace android;

 int main(int argc, char** argv)
  {
     int sum = 0;
     sp<ITestBinderService> mTestBinserService;
     if (mTestBinserService.get() == 0) {
         sp<IServiceManager> sm = defaultServiceManager();
         sp<IBinder> binder;
         do {
             binder = sm->getService(String16("my.test.binder"));
             if (binder != 0)
                 break;
                 LOGI("getService fail");
             usleep(500000); // 0.5 s
         } while (true);
         mTestBinserService = interface_cast<ITestBinderService> (binder);
         LOGE_IF(mTestBinserService == 0, "no ITestBinserService!?");
     }
     sum = mTestBinserService->add(3, 4);
     LOGI("sum = %d", sum);
     return 0;

 }

这里先根据名字获取Service，再使用其提供的相应 服务

看下串口打印，

启动service:

 C:\adb>adb shell
 # cd /system/bin
 cd /system/bin
 # chmod 777 main_*
 chmod 777 main_*
 # ./main_testBinder
 ./main_testBinder

client:

 I/ServiceManager( 1369): Waiting for service my.test.binder...
 I/ServiceManager( 1369): Waiting for service my.test.binder...
 I/ServiceManager( 1369): Waiting for service my.test.binder...
 I/ServiceManager( 1369): Waiting for service my.test.binder...
 I/ServiceManager( 1369): Waiting for service my.test.binder...
 I/PlayServiceManager-JNI( 1369): getService fail
 I/ServiceManager( 1369): Waiting for service my.test.binder...
 I/ServiceManager( 1369): Waiting for service my.test.binder...
 I/ServiceManager( 1369): Waiting for service my.test.binder...
 I/ServiceManager( 1369): Waiting for service my.test.binder...
 I/        ( 1373): TestBinderService before
 I/TestBinderService( 1373): Enter TestBinderService::instantiate
 D/TestBinderService( 1373):  TestBinderServicet
 D/TestBinderService( 1373): ServiceManager addService ret=0
 D/TestBinderService( 1373): instantiate> end
 I/        ( 1373): TestBinderService End
 I/ITeeveePlayerService( 1369): Enter BpTestBinderService add,a = 3 , b = 4
 I/ITeeveePlayerService( 1373): Enter BnTestBinderService add,a = 3 , b = 4
 I/TestBinderService( 1373): TestBinderService::add a = 3, b = 4.
 I/ITeeveePlayerService( 1373): BnTestBinderService sum = 7
 I/ITeeveePlayerService( 1369): BpTestBinderService sum = 7
 I/PlayServiceManager-JNI( 1369): sum = 7

前面 的Waiting for service my.test.binder...是在还没有启动service的时候打印出来的

这样，需要使用TestBinserService 提供的服务时，只需要先获取其service,再使用其提供的方法

相关代码：

http://download.csdn.net/detail/new_abc/4673623