Android onLocationChanged未触发

我正在尝试获取用户位置，但似乎没有调用LocationListener listner类的onLocationChanged

我已经在下面发布了我的代码，任何帮助都将不胜感激

locationManager = (LocationManager)getActivity().getSystemService(Context.LOCATION_SERVICE);

checkForNetwork();

setLocationProvider();

用于检查哪个位置提供程序可用的代码

private void checkForNetwork() {

    try {
        fromGPS = locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER);

    } catch (Exception e){
        Toast.makeText(getActivity(), "GPS not available, trying to get location from network", Toast.LENGTH_SHORT).show();

    }

        try {

            fromNetwork = locationManager.isProviderEnabled(LocationManager.NETWORK_PROVIDER);

        } catch (Exception e) {
            Toast.makeText(getActivity(), "Network not available", Toast.LENGTH_SHORT).show();

        }

}

请求位置更新的代码：

private void setLocationProvider() {

    if (fromGPS){
        locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER,
                0, 0, locationListener);
        net.setText("Location from GPS");

    } else if (fromNetwork){
        locationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER,
                0, 0, locationListener);
        net.setText("Location from network");

    } else {
        net.setText("No location provider is enabled");
    }
}

LocationListener类：

private class myLocationListener implements LocationListener {

    @Override
    public void onLocationChanged(Location location) {

        Toast.makeText(getActivity(), "Location changed", Toast.LENGTH_SHORT).show();

        if (location != null){


        } else {

            lat.setText("Location is null");
        }
    }

    @Override
    public void onStatusChanged(String provider, int status, Bundle extras) {

    }

    @Override
    public void onProviderEnabled(String provider) {

    }

    @Override
    public void onProviderDisabled(String provider) {

    }
}