IActivityManager ActivityManagerNative ActivityManagerService之间如何进行工作

总结：IActivityManager调用函数最终会调用ActivityManagerService中的对应实现

IActivityManager 定义的接口。 app侧的proxy <—->ActivityManagerProxy
比如IActivityManager定义接口startActivityFromRecents

class ActivityManagerProxy implements IActivityManager
{
    public ActivityManagerProxy(IBinder remote)
    {
        mRemote = remote;
    }
    public IBinder asBinder()
    {
        return mRemote;
    }
mRemote.transact(START_ACTIVITY_FROM_RECENTS_TRANSACTION, data, reply, 0);

ActivityManagerNative的声明

public abstract class ActivityManagerNative extends Binder implements IActivityManager

onTransact中的处理

    case START_ACTIVITY_FROM_RECENTS_TRANSACTION:
        {
            data.enforceInterface(IActivityManager.descriptor);
            final int taskId = data.readInt();
            final Bundle options =
                    data.readInt() == 0 ? null : Bundle.CREATOR.createFromParcel(data);
            final int result = startActivityFromRecents(taskId, options);
            reply.writeNoException();
            reply.writeInt(result);
            return true;
        }

ActivityManagerService的声明

ActivityManagerService extends ActivityManagerNative 

真正的实现代码

    @Override
    public final int startActivityFromRecents(int taskId, Bundle bOptions) {
        if (checkCallingPermission(START_TASKS_FROM_RECENTS) != PackageManager.PERMISSION_GRANTED) {
            String msg = "Permission Denial: startActivityFromRecents called without " +
                    START_TASKS_FROM_RECENTS;
            Slog.w(TAG, msg);
            throw new SecurityException(msg);
        }
        final long origId = Binder.clearCallingIdentity();
        try {
            synchronized (this) {
                return mStackSupervisor.startActivityFromRecentsInner(taskId, bOptions);
            }
        } finally {
            Binder.restoreCallingIdentity(origId);
        }
    }

因此通过IActivityManager调用函数最终会调用ActivityManagerService中的对应实现