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


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