Unable to execute inner statements of a for loop in Dart

I am trying to display an image in my weather app based on the current weather condition.

I have a jsonConditionsDay variable which stores JSON data fetched from https://www.weatherapi.com/docs/conditions.json.

I have a List<String> conditionsDayImgUrls = []; //network image urls contained in this which stores image urls.

Current weather data is fetched using dio from https://www.weatherapi.com/api-explorer.aspx#forecast and stored in a variable jsonData.

Now when I'm calling the following function String getCurrentConditionsBgImgForDay(String str) I am not getting the desired image from the conditionsDayImgUrls list, instead I'm only getting the first image of the list.

Code for getCurrentConditionsBgImgForDay in global_variables.dart:

String getCurrentConditionsBgImgForDay(String str) {
  int i;
  for (i = 0; i < jsonConditions.length; i++) {
    if (str == jsonConditions[i]["day"]) {
      return conditionsDayImgUrls[i];
    }
  }
  //print(i);
  return conditionsDayImgUrls[0];
}

The following code in current_weather_screen.dart tries to display the desired weather image based on current weather condition:

Container(
                                        width: screenWidth,
                                        height: screenHeight,
                                        decoration: BoxDecoration(
                                          image: DecorationImage(
                                            image: NetworkImage(
                                                getCurrentConditionsBgImgForDay(
                                                    jsonData["current"]
                                                        ["condition"]["text"])),
                                            fit: BoxFit.fill,
                                          ),
                                        ),
                                      ),

What is wrong in my code that is preventing it from displaying the correct weather image and how to solve it?