onProviderEnabled not working?

问题

For switching between GPS & Network location provider I just tried in a way like this, to identify when a provider is disabled switch to another, but my onProviderEnabled() is not getting invoked

public void onProviderDisabled(String provider) {
  Toast.makeText(TrackerService.this, "Disabled : " + provider, Toast.LENGTH_LONG).show();
}
public void onProviderEnabled(String provider) {
  Toast.makeText(TrackerService.this, "Enabled : " + provider, Toast.LENGTH_LONG).show()

回答1:

Define a location listener like the following:

LocationListener locationListener = new LocationListener() {
            public void onLocationChanged(Location location) {

            }
            public void onProviderDisabled(String provider) {}
            public void onProviderEnabled(String provider) {}
            public void onStatusChanged(String provider, int status, Bundle extras) {}
        };

Then :

LocationManager lm = (LocationManager) getSystemService(Context.LOCATION_SERVICE); 
  lm.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, locationListener);
  lm.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 0, 0, locationListener);

来源：https://stackoverflow.com/questions/8699262/onproviderenabled-not-working