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关联类
ServiceManager.java
framework 核心类，保存所有service的 binder引用，提供service添加和查询接口。
是android中binder服务的管家，一般binder服务会先注册到servicemanager中，
然后其他客户端会通过servicemanager来获取目标binder的proxy binder，
这时候就可以通过获取的proxy binder进行ipc调用。
IServiceManager.java
提供ServiceManagerNative中的内部类ServiceManagerProxy跨进程调用的接口
ServiceManagerNative.java
是个Binder类，需要了解AIDL的组成结构
IInterface.java
提供基础AIDL功能
与SystemServiceManager的区别
SystemServer中启动的各种服务，在ServiceManager中注册的是用于进程间通信的，LocalServces中注册的用于system_server进程内部通信的。
LocalServices中都是静态方法，由SystemServiceManager启动并管理的服务都是是继承了SystemService的。SystemService中很多方法都是通过操作LocalServices，ActivityManagerService也会有相关内部类的实例注册到LocalServices，这个实例是提供system server进程内部的其他服务操作AMS的接口。把该服务在system server内部使用到的接口封装到一个独立的类中，把这个类的实例注册到LocalServices。
给其他进程调用的接口封装到一个Binder类中，然后注册到ServiceManager中。
使用
可参考SystemServer中的调用
代码路径
frameworks/base/core/java/android/os/ServiceManager.java
frameworks/base/core/java/android/os/IServiceManager.java
frameworks/base/core/java/android/os/ServiceManagerNative.java
frameworks/base/core/java/android/os/IInterface.java
源码
IServiceManager, ServiceManagerNative, ServiceManagerProxy要理解AIDL
frameworks/base/core/java/android/os/ServiceManager.java
package android.os;
import android.annotation.UnsupportedAppUsage;
import android.util.ArrayMap;
import android.util.Log;
import com.android.internal.annotations.GuardedBy;
import com.android.internal.os.BinderInternal;
import com.android.internal.util.StatLogger;
import java.util.Map;
/** @hide */
public final class ServiceManager {
private static final String TAG = "ServiceManager";
private static final Object sLock = new Object();
// IserviceManager对象，用于IPC访问，继承自IInterface
@UnsupportedAppUsage
private static IServiceManager sServiceManager;
/**
* Cache for the "well known" services, such as WM and AM.
*/
// 一些关键的服务信息存储在这里
// 由ActivityManagerService通过ActivityThread调用ServiceManager.initServiceCache
// 传进来的。实际上ActivityManagerService中在添加的时候，调用的事Service的getService方法。
@UnsupportedAppUsage
private static Map sCache = new ArrayMap();
/**
* ...
* 应该不是太重要的略过
*/
// 获取IServiceManager对象，用于IPC调用
@UnsupportedAppUsage
private static IServiceManager getIServiceManager() {
if (sServiceManager != null) {
return sServiceManager;
}
// Find the service manager
// ServiceManagerNative是binder，实现了IServiceManager
sServiceManager = ServiceManagerNative
.asInterface(Binder.allowBlocking(BinderInternal.getContextObject()));
return sServiceManager;
}
/**
* Returns a reference to a service with the given name.
*
* @param name the name of the service to get
* @return a reference to the service, or null if the service doesn't exist
*/
// 根据传进来的服务名称，获取对应服务。
@UnsupportedAppUsage
public static IBinder getService(String name) {
try {
// cache中有就直接返回（ActivityManagerService中追加的）。
// 剩下的需要IPC去调用获取
IBinder service = sCache.get(name);
if (service != null) {
return service;
} else {
return Binder.allowBlocking(rawGetService(name));
}
} catch (RemoteException e) {
Log.e(TAG, "error in getService", e);
}
return null;
}
/**
* Returns a reference to a service with the given name, or throws
* {@link NullPointerException} if none is found.
*
* @hide
*/
// 同样是根据名称获取服务，内部就是getService
public static IBinder getServiceOrThrow(String name) throws ServiceNotFoundException {
final IBinder binder = getService(name);
if (binder != null) {
return binder;
} else {
throw new ServiceNotFoundException(name);
}
}
/**
* Place a new @a service called @a name into the service
* manager.
*
* @param name the name of the new service
* @param service the service object
*/
@UnsupportedAppUsage
public static void addService(String name, IBinder service) {
addService(name, service, false, IServiceManager.DUMP_FLAG_PRIORITY_DEFAULT);
}
/**
* Place a new @a service called @a name into the service
* manager.
*
* @param name the name of the new service
* @param service the service object
* @param allowIsolated set to true to allow isolated sandboxed processes
* to access this service
*/
@UnsupportedAppUsage
public static void addService(String name, IBinder service, boolean allowIsolated) {
addService(name, service, allowIsolated, IServiceManager.DUMP_FLAG_PRIORITY_DEFAULT);
}
/**
* Place a new @a service called @a name into the service
* manager.
*
* @param name the name of the new service
* @param service the service object
* @param allowIsolated set to true to allow isolated sandboxed processes
* @param dumpPriority supported dump priority levels as a bitmask
* to access this service
*/
// IPC调用，添加服务
@UnsupportedAppUsage
public static void addService(String name, IBinder service, boolean allowIsolated,
int dumpPriority) {
try {
getIServiceManager().addService(name, service, allowIsolated, dumpPriority);
} catch (RemoteException e) {
Log.e(TAG, "error in addService", e);
}
}
/**
* Retrieve an existing service called @a name from the
* service manager. Non-blocking.
*/
// 检查服务是否存在
@UnsupportedAppUsage
public static IBinder checkService(String name) {
try {
IBinder service = sCache.get(name);
if (service != null) {
return service;
} else {
return Binder.allowBlocking(getIServiceManager().checkService(name));
}
} catch (RemoteException e) {
Log.e(TAG, "error in checkService", e);
return null;
}
}
/**
* Return a list of all currently running services.
* @return an array of all currently running services, or null in
* case of an exception
*/
// 查看所有添加的服务
@UnsupportedAppUsage
public static String[] listServices() {
try {
return getIServiceManager().listServices(IServiceManager.DUMP_FLAG_PRIORITY_ALL);
} catch (RemoteException e) {
Log.e(TAG, "error in listServices", e);
return null;
}
}
/**
* This is only intended to be called when the process is first being brought
* up and bound by the activity manager. There is only one thread in the process
* at that time, so no locking is done.
*
* @param cache the cache of service references
* @hide
*/
// 在ActivityThread中由ActivityManagerService中添加一些关键服务
public static void initServiceCache(Map cache) {
if (sCache.size() != 0) {
throw new IllegalStateException("setServiceCache may only be called once");
}
sCache.putAll(cache);
}
private static IBinder rawGetService(String name) throws RemoteException {
// 通过IServiceManager获取服务IBinder对象
final IBinder binder = getIServiceManager().getService(name);
return binder;
}
}
frameworks/base/core/java/android/os/IServiceManager.java
package android.os;
import android.annotation.UnsupportedAppUsage;
/**
* Basic interface for finding and publishing system services.
*
* An implementation of this interface is usually published as the
* global context object, which can be retrieved via
* BinderNative.getContextObject(). An easy way to retrieve this
* is with the static method BnServiceManager.getDefault().
*
* @hide
*/
public interface IServiceManager extends IInterface
{
/**
* Retrieve an existing service called @a name from the
* service manager. Blocks for a few seconds waiting for it to be
* published if it does not already exist.
*/
@UnsupportedAppUsage
IBinder getService(String name) throws RemoteException;
/**
* Retrieve an existing service called @a name from the
* service manager. Non-blocking.
*/
@UnsupportedAppUsage
IBinder checkService(String name) throws RemoteException;
/**
* Place a new @a service called @a name into the service
* manager.
*/
void addService(String name, IBinder service, boolean allowIsolated, int dumpFlags)
throws RemoteException;
/**
* Return a list of all currently running services.
*/
String[] listServices(int dumpFlags) throws RemoteException;
/**
* Assign a permission controller to the service manager. After set, this
* interface is checked before any services are added.
*/
void setPermissionController(IPermissionController controller)
throws RemoteException;
static final String descriptor = "android.os.IServiceManager";
int GET_SERVICE_TRANSACTION = IBinder.FIRST_CALL_TRANSACTION;
int CHECK_SERVICE_TRANSACTION = IBinder.FIRST_CALL_TRANSACTION+1;
int ADD_SERVICE_TRANSACTION = IBinder.FIRST_CALL_TRANSACTION+2;
int LIST_SERVICES_TRANSACTION = IBinder.FIRST_CALL_TRANSACTION+3;
int CHECK_SERVICES_TRANSACTION = IBinder.FIRST_CALL_TRANSACTION+4;
int SET_PERMISSION_CONTROLLER_TRANSACTION = IBinder.FIRST_CALL_TRANSACTION+5;
/*
* Must update values in IServiceManager.h
*/
/* Allows services to dump sections according to priorities. */
int DUMP_FLAG_PRIORITY_CRITICAL = 1 << 0;
int DUMP_FLAG_PRIORITY_HIGH = 1 << 1;
int DUMP_FLAG_PRIORITY_NORMAL = 1 << 2;
/**
* Services are by default registered with a DEFAULT dump priority. DEFAULT priority has the
* same priority as NORMAL priority but the services are not called with dump priority
* arguments.
*/
int DUMP_FLAG_PRIORITY_DEFAULT = 1 << 3;
int DUMP_FLAG_PRIORITY_ALL = DUMP_FLAG_PRIORITY_CRITICAL | DUMP_FLAG_PRIORITY_HIGH
| DUMP_FLAG_PRIORITY_NORMAL | DUMP_FLAG_PRIORITY_DEFAULT;
/* Allows services to dump sections in protobuf format. */
int DUMP_FLAG_PROTO = 1 << 4;
}
frameworks/base/core/java/android/os/ServiceManagerNative.java
package android.os;
import android.annotation.UnsupportedAppUsage;
import java.util.ArrayList;
/**
* Native implementation of the service manager. Most clients will only
* care about getDefault() and possibly asInterface().
* @hide
*/
public abstract class ServiceManagerNative extends Binder implements IServiceManager
{
/**
* Cast a Binder object into a service manager interface, generating
* a proxy if needed.
*/
@UnsupportedAppUsage
static public IServiceManager asInterface(IBinder obj)
{
if (obj == null) {
return null;
}
IServiceManager in =
(IServiceManager)obj.queryLocalInterface(descriptor);
if (in != null) {
return in;
}
return new ServiceManagerProxy(obj);
}
public ServiceManagerNative()
{
attachInterface(this, descriptor);
}
}
class ServiceManagerProxy implements IServiceManager {
public ServiceManagerProxy(IBinder remote) {
mRemote = remote;
}
public IBinder asBinder() {
return mRemote;
}
@UnsupportedAppUsage
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;
}
public IBinder checkService(String name) throws RemoteException {
Parcel data = Parcel.obtain();
Parcel reply = Parcel.obtain();
data.writeInterfaceToken(IServiceManager.descriptor);
data.writeString(name);
mRemote.transact(CHECK_SERVICE_TRANSACTION, data, reply, 0);
IBinder binder = reply.readStrongBinder();
reply.recycle();
data.recycle();
return binder;
}
public void addService(String name, IBinder service, boolean allowIsolated, int dumpPriority)
throws RemoteException {
Parcel data = Parcel.obtain();
Parcel reply = Parcel.obtain();
data.writeInterfaceToken(IServiceManager.descriptor);
data.writeString(name);
data.writeStrongBinder(service);
data.writeInt(allowIsolated ? 1 : 0);
data.writeInt(dumpPriority);
mRemote.transact(ADD_SERVICE_TRANSACTION, data, reply, 0);
reply.recycle();
data.recycle();
}
public String[] listServices(int dumpPriority) throws RemoteException {
ArrayList services = new ArrayList();
int n = 0;
while (true) {
Parcel data = Parcel.obtain();
Parcel reply = Parcel.obtain();
data.writeInterfaceToken(IServiceManager.descriptor);
data.writeInt(n);
data.writeInt(dumpPriority);
n++;
try {
boolean res = mRemote.transact(LIST_SERVICES_TRANSACTION, data, reply, 0);
if (!res) {
break;
}
} catch (RuntimeException e) {
// The result code that is returned by the C++ code can
// cause the call to throw an exception back instead of
// returning a nice result... so eat it here and go on.
break;
}
services.add(reply.readString());
reply.recycle();
data.recycle();
}
String[] array = new String[services.size()];
services.toArray(array);
return array;
}
public void setPermissionController(IPermissionController controller)
throws RemoteException {
Parcel data = Parcel.obtain();
Parcel reply = Parcel.obtain();
data.writeInterfaceToken(IServiceManager.descriptor);
data.writeStrongBinder(controller.asBinder());
mRemote.transact(SET_PERMISSION_CONTROLLER_TRANSACTION, data, reply, 0);
reply.recycle();
data.recycle();
}
@UnsupportedAppUsage
private IBinder mRemote;
}