码迷，mamicode.com
首页 > 移动开发 > 详细

android 进程间通信---Service Manager（2）

时间：2015-09-20 10:24:24      阅读：253      评论：0      收藏：0      [点我收藏+]

标签：

关于servicemanager的设计：

技术分享

还是这张结构图，由于ProcessState & IPCThreadState是与binder deriver交互的，

所以对于client端来说BpBinder以下的部分是透明的。

我们从Activity的getsystemservice来一步步分析整个servicemanager提供服务的过程。

在contextImple.java 中

        registerService(ALARM_SERVICE, new ServiceFetcher() {
                public Object createService(ContextImpl ctx) {
                    IBinder b = ServiceManager.getService(ALARM_SERVICE);
                    IAlarmManager service = IAlarmManager.Stub.asInterface(b);
                    return new AlarmManager(service, ctx);
                }});

注册的代码是static block的形式。

    @Override
    public Object getSystemService(String name) {
        ServiceFetcher fetcher = SYSTEM_SERVICE_MAP.get(name);
        return fetcher == null ? null : fetcher.getService(this);
    }

getservice：

public Object getService(ContextImpl ctx) {
            ArrayList<Object> cache = ctx.mServiceCache;
            Object service;
            synchronized (cache) {
                if (cache.size() == 0) {
                    // Initialize the cache vector on first access.
                    // At this point sNextPerContextServiceCacheIndex
                    // is the number of potential services that are
                    // cached per-Context.
                    for (int i = 0; i < sNextPerContextServiceCacheIndex; i++) {
                        cache.add(null);
                    }
                } else {
                    service = cache.get(mContextCacheIndex);
                    if (service != null) {
                        return service;
                    }
                }
                service = createService(ctx);
                cache.set(mContextCacheIndex, service);
                return service;
            }
        }

所以可以看到最终调用就是注册函数的内容

 IBinder b = ServiceManager.getService(ALARM_SERVICE);

ServiceManager.java:

    public static IBinder getService(String name) {
        try {
            IBinder service = sCache.get(name);
            if (service != null) {
                return service;
            } else {
                return getIServiceManager().getService(name);
            }
        } catch (RemoteException e) {
            Log.e(TAG, "error in getService", e);
        }
        return null;
    }

我们应用层看到的service对象是IBinder。

然后我们看看IServiceManager

    private static IServiceManager getIServiceManager() {
        if (sServiceManager != null) {
            return sServiceManager;
        }

        // Find the service manager
        sServiceManager = ServiceManagerNative.asInterface(BinderInternal.getContextObject());
        return sServiceManager;
    }
技术分享 
    /**
     * Return the global "context object" of the system.  This is usually
     * an implementation of IServiceManager, which you can use to find
     * other services.
     */
    public static final native IBinder getContextObject();
getContextObject

可以看到注释说明，返回的就是全局唯一的ServiceManager对象。

class ServiceManagerProxy implements IServiceManager {
    public ServiceManagerProxy(IBinder remote) {
        mRemote = remote;
    }
    
    public IBinder asBinder() {
        return mRemote;
    }
    
    public IBinder getService(String name) throws RemoteException {
        Parcel data = Parcel.obtain();
        Parcel reply = Parcel.obtain();
        data.writeInterfaceToken(IServiceManager.descriptor);
        data.writeString(name);
        mRemote.transact(GET_SERVICE_TRANSACTION, data, reply, 0);
        IBinder binder = reply.readStrongBinder();
        reply.recycle();
        data.recycle();
        return binder;
    }

 

AIDL的实现：

网上有很多关于AIDL的讨论，解释等等。

AIDL是什么？

Android Interface definition language:

所以aidl是google为了便利的实现binder机制，而创建的一种语言。

AIDL的目的是为了便于开发者可以快速书写创建进程间通信的一种语言，或者代码。

package com.htc.globalsearch.imagesearch.service.aidl;
import com.htc.globalsearch.imagesearch.service.aidl.PersonImageItem;
import com.htc.globalsearch.imagesearch.service.aidl.ICallBack;

interface IBuildService{
    int getServiceStatus();
    int findPerson(String path,int filter);
    void registerCallback(ICallBack cb);     
    void unregisterCallback(ICallBack cb);  
}

看看生成后变成什么？

 

技术分享 
/*
 * This file is auto-generated.  DO NOT MODIFY.
 * Original file: D:\\AndroidDev\\github\\Example\\Examples\\ImageSearch\\src\\com\\htc\\globalsearch\\imagesearch\\service\\aidl\\IBuildService.aidl
 */
package com.htc.globalsearch.imagesearch.service.aidl;
public interface IBuildService extends android.os.IInterface
{
/** Local-side IPC implementation stub class. */
public static abstract class Stub extends android.os.Binder implements com.htc.globalsearch.imagesearch.service.aidl.IBuildService
{
private static final java.lang.String DESCRIPTOR = "com.htc.globalsearch.imagesearch.service.aidl.IBuildService";
/** Construct the stub at attach it to the interface. */
public Stub()
{
this.attachInterface(this, DESCRIPTOR);
}
/**
 * Cast an IBinder object into an com.htc.globalsearch.imagesearch.service.aidl.IBuildService interface,
 * generating a proxy if needed.
 */
public static com.htc.globalsearch.imagesearch.service.aidl.IBuildService asInterface(android.os.IBinder obj)
{
if ((obj==null)) {
return null;
}
android.os.IInterface iin = obj.queryLocalInterface(DESCRIPTOR);
if (((iin!=null)&&(iin instanceof com.htc.globalsearch.imagesearch.service.aidl.IBuildService))) {
return ((com.htc.globalsearch.imagesearch.service.aidl.IBuildService)iin);
}
return new com.htc.globalsearch.imagesearch.service.aidl.IBuildService.Stub.Proxy(obj);
}
@Override public android.os.IBinder asBinder()
{
return this;
}
@Override public boolean onTransact(int code, android.os.Parcel data, android.os.Parcel reply, int flags) throws android.os.RemoteException
{
switch (code)
{
case INTERFACE_TRANSACTION:
{
reply.writeString(DESCRIPTOR);
return true;
}
case TRANSACTION_getServiceStatus:
{
data.enforceInterface(DESCRIPTOR);
int _result = this.getServiceStatus();
reply.writeNoException();
reply.writeInt(_result);
return true;
}
case TRANSACTION_findPerson:
{
data.enforceInterface(DESCRIPTOR);
java.lang.String _arg0;
_arg0 = data.readString();
int _arg1;
_arg1 = data.readInt();
int _result = this.findPerson(_arg0, _arg1);
reply.writeNoException();
reply.writeInt(_result);
return true;
}
case TRANSACTION_registerCallback:
{
data.enforceInterface(DESCRIPTOR);
com.htc.globalsearch.imagesearch.service.aidl.ICallBack _arg0;
_arg0 = com.htc.globalsearch.imagesearch.service.aidl.ICallBack.Stub.asInterface(data.readStrongBinder());
this.registerCallback(_arg0);
reply.writeNoException();
return true;
}
case TRANSACTION_unregisterCallback:
{
data.enforceInterface(DESCRIPTOR);
com.htc.globalsearch.imagesearch.service.aidl.ICallBack _arg0;
_arg0 = com.htc.globalsearch.imagesearch.service.aidl.ICallBack.Stub.asInterface(data.readStrongBinder());
this.unregisterCallback(_arg0);
reply.writeNoException();
return true;
}
}
return super.onTransact(code, data, reply, flags);
}
private static class Proxy implements com.htc.globalsearch.imagesearch.service.aidl.IBuildService
{
private android.os.IBinder mRemote;
Proxy(android.os.IBinder remote)
{
mRemote = remote;
}
@Override public android.os.IBinder asBinder()
{
return mRemote;
}
public java.lang.String getInterfaceDescriptor()
{
return DESCRIPTOR;
}
@Override public int getServiceStatus() throws android.os.RemoteException
{
android.os.Parcel _data = android.os.Parcel.obtain();
android.os.Parcel _reply = android.os.Parcel.obtain();
int _result;
try {
_data.writeInterfaceToken(DESCRIPTOR);
mRemote.transact(Stub.TRANSACTION_getServiceStatus, _data, _reply, 0);
_reply.readException();
_result = _reply.readInt();
}
finally {
_reply.recycle();
_data.recycle();
}
return _result;
}
@Override public int findPerson(java.lang.String path, int filter) throws android.os.RemoteException
{
android.os.Parcel _data = android.os.Parcel.obtain();
android.os.Parcel _reply = android.os.Parcel.obtain();
int _result;
try {
_data.writeInterfaceToken(DESCRIPTOR);
_data.writeString(path);
_data.writeInt(filter);
mRemote.transact(Stub.TRANSACTION_findPerson, _data, _reply, 0);
_reply.readException();
_result = _reply.readInt();
}
finally {
_reply.recycle();
_data.recycle();
}
return _result;
}
@Override public void registerCallback(com.htc.globalsearch.imagesearch.service.aidl.ICallBack cb) throws android.os.RemoteException
{
android.os.Parcel _data = android.os.Parcel.obtain();
android.os.Parcel _reply = android.os.Parcel.obtain();
try {
_data.writeInterfaceToken(DESCRIPTOR);
_data.writeStrongBinder((((cb!=null))?(cb.asBinder()):(null)));
mRemote.transact(Stub.TRANSACTION_registerCallback, _data, _reply, 0);
_reply.readException();
}
finally {
_reply.recycle();
_data.recycle();
}
}
@Override public void unregisterCallback(com.htc.globalsearch.imagesearch.service.aidl.ICallBack cb) throws android.os.RemoteException
{
android.os.Parcel _data = android.os.Parcel.obtain();
android.os.Parcel _reply = android.os.Parcel.obtain();
try {
_data.writeInterfaceToken(DESCRIPTOR);
_data.writeStrongBinder((((cb!=null))?(cb.asBinder()):(null)));
mRemote.transact(Stub.TRANSACTION_unregisterCallback, _data, _reply, 0);
_reply.readException();
}
finally {
_reply.recycle();
_data.recycle();
}
}
}
static final int TRANSACTION_getServiceStatus = (android.os.IBinder.FIRST_CALL_TRANSACTION + 0);
static final int TRANSACTION_findPerson = (android.os.IBinder.FIRST_CALL_TRANSACTION + 1);
static final int TRANSACTION_registerCallback = (android.os.IBinder.FIRST_CALL_TRANSACTION + 2);
static final int TRANSACTION_unregisterCallback = (android.os.IBinder.FIRST_CALL_TRANSACTION + 3);
}
public int getServiceStatus() throws android.os.RemoteException;
public int findPerson(java.lang.String path, int filter) throws android.os.RemoteException;
public void registerCallback(com.htc.globalsearch.imagesearch.service.aidl.ICallBack cb) throws android.os.RemoteException;
public void unregisterCallback(com.htc.globalsearch.imagesearch.service.aidl.ICallBack cb) throws android.os.RemoteException;
}
IBuildService.java
public static abstract class Stub extends android.os.Binder implements com.htc.globalsearch.imagesearch.service.aidl.IBuildService

关键是这个class，stub继承自binder，而且实现了IbuildService的接口。

在看service

private class ImageSearchBuildServiceImpl extends IBuildService.Stub{

所以，service是实现了Stub的内容，进而可以实现这个方法。

而service的onbind就是返回这个stub

    @Override
    public IBinder onBind(Intent intent) {
        mCurrentCookie = intent.getLongExtra("cookie",-1);
        Log.i(TAG, "[onBind] mCurrentCookie:"+mCurrentCookie);
        iServiceImpl = new ImageSearchBuildServiceImpl(mImageSearchOperator);
        return iServiceImpl;
    }

通过bindservice，会把这个Ibinder对象返回给client端。

  

android 进程间通信---Service Manager（2）

标签：

原文地址：http://www.cnblogs.com/deman/p/4792400.html
踩
(0)
赞
(0)
   
举报
评论 一句话评论（0）
登录后才能评论！
分享档案
更多>
2021年07月29日 (22)
2021年07月28日 (40)
2021年07月27日 (32)
2021年07月26日 (79)
2021年07月23日 (29)
2021年07月22日 (30)
2021年07月21日 (42)
2021年07月20日 (16)
2021年07月19日 (90)
2021年07月16日 (35)
周排行
mamicode.com排行更多图片
更多
友情链接
兰亭集智   国之画   百度统计   站长统计   阿里云   chrome插件   新版天听网
关于我们 - 联系我们 - 留言反馈
© 2014 mamicode.com 版权所有  联系我们:gaon5@hotmail.com
迷上了代码！