Adding elements to List in Flutter from For statement?

Question

I'm receiving the following error while trying to add elements from my for loop to my List...

NoSuchMethodError: The method 'addAll' was called on null.
    Receiver: null
    Tried calling: addAll("LrWr826cd3Y")

Here is my code...

Future getData() async {
    //Map videoId;

    String url = 'https://Youtube API';
    var httpClient = createHttpClient();
    var response = await httpClient.read(url);
    Map data = JSON.decode(response);
    var videos = data['items']; //returns a List of Maps

    List searchTitles;
    List searchIds;
    List searchImages;

    for (var items in videos) {
      //iterate over the list
      Map myMap = items; //store each map
      final video = (myMap['id'] as Map);
      print(video['videoId']);
      searchIds.addAll(video['videoId']);
      final details = (myMap['snippet'] as Map);
      final videoimage = (details['thumbnails'] as Map);
      final medium = (videoimage['medium'] as Map);

    }

    setState(() { });

    if (!mounted) return;
  }

print(video['videoId']); successfully lists the 3 Youtube video ids as Strings. searchIds.addAll(video['videoId']); throws the error. I've tried both searchIds.add and searchIds.addAll. Where am I going wrong?

I would like to eventually push these lists to my List class here..

class CardInfo {
  //Constructor
  List id;
  List title;
  List video;

  CardInfo.fromJson(List json) {
    this.id;
    this.title;
    this.video;
  }
}

Gowthaman M · Accepted Answer · 2019-04-25 12:34:24Z

13

You are not instantiating your searchIds object. add this

List searchIds = new ArrayList<>();

(Or)

List searchIds = new List();

edited Apr 25, 2019 at 12:34

Gowthaman M

8,3029 gold badges40 silver badges57 bronze badges

answered Sep 23, 2017 at 6:37

milad zahedi

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4 Comments

Charles Jr Over a year ago

This is how I got it to work for Flutter... List searchIds = new List();

milad zahedi Over a year ago

I see your problem is fixed. Good job.

Gowthaman M Over a year ago

List searchIds = new List(); this is worked for me.

poonam kalra Over a year ago

You can also use List searchIds = [];

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