'A non-null String must be provided to a Text widget' (Flutter)

问题

I've tried to fix this with the following code but I'm afraid the error is still prevalent:

The following assertion was thrown building:
A non-null String must be provided to a Text widget.
'package:flutter/src/widgets/text.dart':
Failed assertion: line 360 pos 10: 'data != null'

child: Row(
            children: [
              Text(
                  (contact.data()['rating'] == null)
                      ? "n/a"
                      : contact.data()['rating'].toString(),
                  style: TextStyle(
                      fontWeight: FontWeight.bold,
                      color: Colors.tealAccent)),
              Padding(
                padding: const EdgeInsets.all(8.0),
                child: CircleAvatar(
                  radius: 25,
                  backgroundImage: AssetImage("assets/girl2.jpg"),
                ),
              ),
              Spacer(),
              Text(
                contact.data()['name'],
                style: TextStyle(
                    fontWeight: FontWeight.w400, color: Colors.tealAccent),
              ),
              Spacer(),
              Text(
                contact.data()['location'],
                style: TextStyle(
                    letterSpacing: 1,
                    fontSize: 10,
                    fontWeight: FontWeight.w300,
                    color: Colors.tealAccent),
              ),
            ],
          ),

How would one go about solving this?

回答1:

You can just add:

contact.data()['rating'] ?? "empty" 

The above will check if the expression on the left is not null, if it is then "empty" will be added to the Text widget. You have to add the condition to the other Text widgets also.

来源：https://stackoverflow.com/questions/64343386/a-non-null-string-must-be-provided-to-a-text-widget-flutter