android中native js中重写方法问题

java代码：

PhoneStateListener phoneStateListener = new PhoneStateListener() {  
        @Override  
        public void onSignalStrengthsChanged(SignalStrength signalStrength) {  
            // TODO Auto-generated method stub  
                        ......  
        }  
};  
((TelephonyManager)getSystemService(Context.TELEPHONY_SERVICE)).listen(phoneStateListener, PhoneStateListener.LISTEN_SIGNAL_STRENGTHS);

listen方法需要传入一个PhoneStateListener 的实例，需要重写onSignalStrengthsChanged方法以供回调。

native js中：

    var main = plus.android.runtimeMainActivity();  
    var telephoneManager = plus.android.invoke(main, "getSystemService", "phone");  
    plus.android.importClass(telephoneManager);  
    var PhoneStateListener = plus.android.importClass("android.telephony.PhoneStateListener");  
    var phoneStateListener = new PhoneStateListener();  
    //这里给onSignalStrengthsChanged 重新赋值，但是onSignalStrengthsChanged 的回调一直没有被调用  
    phoneStateListener.onSignalStrengthsChanged = function(signalStrength) {  
        ......  
    };  
    telephoneManager.listen(phoneStateListener, PhoneStateListener.LISTEN_SIGNAL_STRENGTHS);