在textformField中输入地名并提交，然后将摄像机位置移动到该位置，并在设备当前位置到目的地之间绘制线，并显示它们之间的距离。但所有这些东西都是完全离线的。
void _onSubmitLocation（）async { final String enteredLocation = locationName.text;

if (enteredLocation.isNotEmpty) {
  try {
    List<geocoding.Location> locations =
        await geocoding.locationFromAddress(enteredLocation);

    if (locations.isNotEmpty) {
      // Assuming the first location returned is the most relevant one
      final geocoding.Location firstLocation = locations.first;
      final LatLng newLocation =
          LatLng(firstLocation.latitude!, firstLocation.longitude!);

      mapController?.animateCamera(CameraUpdate.newLatLngZoom(
        newLocation,
        14, // You can adjust the zoom level as needed
      ));
    } else {
      // Handle case when no locations are found for the entered address
      ScaffoldMessenger.of(context).showSnackBar(SnackBar(
        content: const Text("Location not found"),
        backgroundColor: Theme.of(context).colorScheme.error,
        duration: const Duration(seconds: 3),
      ));
    }
  } catch (e) {
    // Handle any errors that may occur during geocoding
    ScaffoldMessenger.of(context).showSnackBar(SnackBar(
      content: const Text("Error finding location"),
      backgroundColor: Theme.of(context).colorScheme.error,
      duration: const Duration(seconds: 3),
    ));
  }
}

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}
这些代码只在网上工作，但我需要离线。如何使这些代码供脱机使用。