中兴V880不能实现网络定位的问题

我最近在研究网络定位，遇到一些问题，能得到provider为network，但是得到的location却为0，不知道什么原因，GPS定位可以成功，但是网络定位就是不行。下面上代码，求高人指点 private void location2(){
//获取到LocationManager对象 
    locationManager = (LocationManager) getSystemService(LOCATION_SERVICE); 

if(locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER))
         {
       provider=LocationManager.GPS_PROVIDER;
 locationManager.requestLocationUpdates(provider, 10000, 0, locationListener2);
             location = locationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);
             if(location != null)
             {
                 lat = location.getLatitude();
                 lon = location.getLongitude();
                 System.out.println("------>"+"GPS定位成功");
              
             }
             else
             {
                           
                              provider=LocationManager.NETWORK_PROVIDER;
              if(provider!=null){
  locationManager.requestLocationUpdates(provider, 10000, 0, locationListener2); 
  }else{
  lat = 0;
                     lon = 0;
                     System.out.println("------>"+"请开启GPS和网络定位");
  }
            
                 location = locationManager.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
                 if(location != null)
                 {
                     lat = location.getLatitude();
                     lon = location.getLongitude();
                     System.out.println("------>"+"GPS已开启但无法定位，network定位成功");
                   //  strAddress = getAddress(latitude, longitude);
                 }
                 else
                 {
                  lat = 0;
                     lon = 0;
                     System.out.println("------>"+"GPS和network已开启但无法定位");
                 }
            }
         }else if(locationManager.isProviderEnabled(LocationManager.NETWORK_PROVIDER)){
          provider=LocationManager.NETWORK_PROVIDER;
          locationManager.requestLocationUpdates(provider, 10000, 0, locationListener2);
          System.out.println("------>是"+provider);
                 location = locationManager.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
                 if(location != null)
                 {
                     lat = location.getLatitude();
                     lon = location.getLongitude();
                     System.out.println("------>"+"GPS未开启，network定位成功");
                   //  strAddress = getAddress(latitude, longitude);
                 }
                 else
                 {
                  lat = 0;
                     lon = 0;
                     System.out.println("------>"+"GPS未开启，network已开启但无法定位");
                 }
         }else{
          lat = 0;
                     lon = 0;
          System.out.println("------>"+"GPS和network均未开启");
         }

} 



 //创建位置监听器 
private LocationListener locationListener2 = new LocationListener(){ 
//位置发生改变时调用 
@Override 
public void onLocationChanged(Location location) { 
Log.d("Location", "onLocationChanged"); 
lat=location.getLatitude(); 
lon=location.getLongitude();  
}   
//provider失效时调用 
@Override 
public void onProviderDisabled(String provider) { 
Log.d("Location", "onProviderDisabled"); 
} 
//provider启用时调用
@Override
public void onProviderEnabled(String provider) {
Log.d("Location", "onProviderEnabled");
}
//状态改变时调用
@Override
public void onStatusChanged(String provider, int status, Bundle extras) {
Log.d("Location", "onStatusChanged");
}
};