native.js不能获取传感器信息

document.addEventListener('plusready', function() {  
                //console.log("所有plus api都应该在此事件发生后调用，否则会出现plus is undefined。"  
                var activity = plus.android.runtimeMainActivity();  
                var Sensor = plus.android.importClass("android.hardware.Sensor");  
                var SensorManager = plus.android.importClass("android.hardware.SensorManager");  
                var Context = plus.android.importClass("android.content.Context");  

                var mSensorManager = activity.getSystemService(Context.SENSOR_SERVICE);  

                var mStepCount = mSensorManager.getDefaultSensor(Sensor.TYPE_STEP_COUNTER);  
                // var mStepDetector = mSensorManager.getDefaultSensor(Sensor.TYPE_STEP_DETECTOR);  

                var listener = plus.android.implements("android.hardware.SensorEventListener", {  
                    onAccuracyChanged: function(sensor, accuracy){  

                    },  
                    onSensorChanged: function(event) {  
                        console.log("传感器类型："+event.plusGetAttribute("sensor").getType());  
                        console.log("当前步数总计："+event.plusGetAttribute("values"));  
                    }  
                });  
                mSensorManager.unregisterListener(listener);  

                // mSensorManager.registerListener(listener, mStepDetector, SensorManager.SENSOR_DELAY_FASTEST);  
                mSensorManager.registerListener(listener, mStepCount, SensorManager.SENSOR_DELAY_FASTEST);  
            });