Unhandled Exception: type 'Null' is not a subtype of type 'String' I get the err-CodePudding

I want to add likes to comments in the application I am writing. In my codes, when I click on the icon in Firebase, I want it to open a field called like and write uid. When I do this in my posts, I succeed, but not in the comments. My codes are as follows. What should I do.

ERROR:flutter/runtime/dart_vm_initializer.cc(41)] Unhandled Exception: type 'Null' is not a subtype of type 'String'

I get the error.

Future<void> LikeComment(String postId, String uid, List likes, String commentId) async {
    try {
      if (likes.contains(uid)) {
        await _firestore.collection('posts').doc(postId).collection('comments').doc(commentId).update({
          'likes': FieldValue.arrayRemove([uid]),
        });
      } else {
        await _firestore.collection('posts').doc(postId).collection('comments').doc(commentId).update({
          'likes': FieldValue.arrayUnion([uid]),
        });
      }
    } catch (e) {
      print(
        e.toString(),
      );
    }
  }

Row(
              children: [
                LikeAnimation(
                  isAnimating: widget.snap['likes']!=null && widget.snap['likes'].contains(myUid),
                  smallLike: true,
                  child: IconButton(
                    onPressed: () async {
                      await FirestoreMethods().LikeComment(
                        widget.snap['postId'],
                        myUid,
                        widget.snap['commentId'],
                        widget.snap['likes'],
                      );
                    },
                    icon: widget.snap['likes']!=null && widget.snap['likes'].contains(myUid)
                        ? const Icon(
                      Icons.favorite,
                      color: Colors.red,
                    )
                        : const Icon(
                      Icons.favorite_border,
                    ),
                  ),
                ),

              ]),

CodePudding user response：

With the information you have given, you need to check your parameters for null values (Debug your code).

Future<void> LikeComment(String postId, String uid, List likes, String commentId) async {
 
print(postId); print(uid); print(likes); print(commentId); // check for the one that returns null and find a way to handle it

//highlight and comment all your below code.

  }

CodePudding user response：

I am refering to make variables nullable and return/handle on null cases.

  Future<void> LikeComment(
      String? postId, String? uid, List? likes, String? commentId) async {
    if (postId == null || uid == null || likes == null || commentId == null) {
      print("postId $postId uid $uid likes $likes  commentId $commentId ");

      return;
    }