snapshot.data[0] throwing "The Method '[ ]' cannot be unconditionally invoked because-CodePudding

Also getting

Try making the call condtional (using ?.) or adding a null check to the target

for the same line(s):

Text("${snapshot.data[index]}")

If I do that I get only the error message from the title.

I have actually copy/pasted a FutureBuilder from another project of mine where it is working perfectly fine but in this one I get this error. The only difference is that in the not working project I see this:

AsyncSnapshot<Object?>

and in the working project I see this:

AsyncSnapshot<dynamic>

If I hover over snapshot

The entire section looks like this:

FutureBuilder(
          future: http_functions.myAsyncFunction(),
          builder: (context, snapshot) {
            return snapshot.hasData
                ? Scrollbar(
                    controller: _scrollController,
                    isAlwaysShown: true,
                    thickness: 4,
                    child: ListView.builder(
                      physics: const AlwaysScrollableScrollPhysics(),
                      shrinkWrap: true,
                      controller: _scrollController,
                      itemCount: 10,
                      itemBuilder: (context, index) {
                        return Card(
                          child: ListTile(
                            title: Text("${snapshot.data[index]}"),
                          ),
                        );
                      },
                    ),
                  )
                : const CircularProgressIndicator();
          },
        )

While myAsyncFunction() returns a List<dynamic> using return json.decode(response.body);

CodePudding user response：

You need to define the type parameter of the FutureBuilder. And cast the snapshot.data to not null by using the ! operator

FutureBuilder<List<dynamic>>(
          future: http_functions.myAsyncFunction(),
          builder: (context, snapshot) {
            return snapshot.hasData
                ? Scrollbar(
                    controller: _scrollController,
                    isAlwaysShown: true,
                    thickness: 4,
                    child: ListView.builder(
                      physics: const AlwaysScrollableScrollPhysics(),
                      shrinkWrap: true,
                      controller: _scrollController,
                      itemCount: 10,
                      itemBuilder: (context, index) {
                        return Card(
                          child: ListTile(
                            title: Text("${snapshot.data![index]}"),
                          ),
                        );
                      },
                    ),
                  )
                : const CircularProgressIndicator();
          },
        )

CodePudding user response：

Use snapshot.data![index] to force that it's not null at this point.

CodePudding user response：

In AsyncSnapshot<Object?> the object is nullable which means it can have a value or can be null. Now you are accessing the object like snapshot.data[index]. Here the snapshot.data can be null and accessing index of a null array can cause error.

So in order to access your array safely replace snapshot.data[index] with snapshot.data?[index] ?? '' or you can use the null assertion operator like this if you are sure that your list can't be null snapshot.data![index].