Java观察者问题

我在Android平台上用Java实现自己的observer时遇到了一些问题。

我创建了一个名为NetworkPathJni的类,它使用一个名为NetworkPathJniObserver的观察者接口类来通知其他对象更改。

下面是NetworkPathJni.java的代码

public class NetworkPathJni {

NetworkPathJniObserver networkPathJniObserver;

  public NetworkPathJni(NetworkPathJniObserver aObserver){

    networkPathJniObserver = aObserver;
    Log.d("Phone", "NetworkPathJni Created" );

  }

  public void NetworkPathStateChanged(int aAvailabilityState){
      Log.d("Phone", "NetworkPathStateChanged new state = " + aAvailabilityState );
      TAvailabilityState availabilityState = intToAvailability(aAvailabilityState);
      Log.d("Phone", "Is SipNetworkPath alive?" +  networkPathJniObserver.isAlive());
      networkPathJniObserver.NetworkPathStateChanged(availabilityState);
      Log.d("Phone", "NetworkPathStateChanged end" );
      Log.d("Phone", "Is SipNetworkPath alive? (2)" +  networkPathJniObserver.isAlive());

  }

这是观察者的代码

public interface NetworkPathJniObserver {

void NetworkPathStateChanged(TAvailabilityState aAvailabilityState);

boolean isAlive();
}

观察者在名为SipNetworkPath的类中实现如下

public class SipNetworkPath implements NetworkPathInterface, NetworkPathJniObserver{

NetworkPathObserverInterface observer;
NetworkPathJni networkPathJni;

public SipNetworkPath(NetworkPathObserverInterface aObserver){
    domainType = aDomainType;
    observer = aObserver;
    networkPathJni = new NetworkPathJni(this);
    Log.d("Phone", "SipNetworkPath created" );
}

//NetworkPathJniObserver

@Override
public void NetworkPathStateChanged(TAvailabilityState availabilityState) {
    Log.d("SipNetworkPath", "SipNetworkPath - Do networkpathstate changed!");
}

@Override
public boolean isAlive() {
    return true;

}

SipNetworkPath的实例如下

public class WifiNetworkPath extends SipNetworkPath{

public WifiNetworkPath(NetworkPathObserverInterface aObserver) {
    super(aObserver);
}

日志显示创建了NetworkPathJni和SipNetworkPath,并调用了NetworkPathStateChanged(int aaavailabilitystate)。

在该方法中,所有的日志记录都会返回,但是观察者不会调用该方法,并且当我在日志记录中询问“SipNetworkPath还活着吗?”时,我会得到false。

观察者类是否丢失了引用或者其他什么,或者在我这样做的方式中是否有错误?