android - Barometric pressure - not getting values -

i've read environment sensors documentation i'm trying pressure, unsuccessfully.

this have:

public class pressure extends activity implements sensoreventlistener{  textview textview; private sensormanager sensormanager;  @override protected void oncreate(bundle savedinstancestate) {     super.oncreate(savedinstancestate);     setcontentview(r.layout.my_pressure);      textview = (textview) findviewbyid(r.id.txt_pressure);      sensormanager = (sensormanager) getsystemservice(service.sensor_service);  }  @override protected void onresume() {     super.onresume();     sensormanager.registerlistener(this,             sensormanager.getdefaultsensor(sensor.type_pressure),             sensormanager.sensor_delay_normal); }  @override public void onsensorchanged(sensorevent event) {     if (event.sensor.gettype() == sensor.type_pressure) {         float[] values = event.values;         textview.settext("" + values[0]);     }  }  @override public void onaccuracychanged(sensor sensor, int accuracy) {  }  @override protected void onpause() {     super.onpause();     sensormanager.unregisterlistener(this); }