It should be a simple thing, but I've been in this for days!

///StreamBuilder
StreamBuilder(
        stream: farmacos.orderBy("nome", descending: false).snapshots(),
        builder: (context, AsyncSnapshot<QuerySnapshot> streamSnapshot) {
          if (!streamSnapshot.hasData) {
            return const Text("No data...");
          }
          return ListView.builder(
              itemCount: streamSnapshot.data!.docs.length,
              itemBuilder: (context, index) => GestureDetector(
                onTap: () {},
                child: Card(
                  color: Colors.amberAccent[100],
                  child: Padding(
                    padding: EdgeInsets.fromLTRB(_margem * .1,
                        _margem * .1, _margem * .1, _margem * .1),
                    child: Row(
                      crossAxisAlignment: CrossAxisAlignment.center,
                      mainAxisAlignment: MainAxisAlignment.spaceBetween,
                      children: [

                        ///Get data from the stream
    
                        Text(streamSnapshot.data!.docs[index]["nome"].toString()),        //Ex: Paracetamol
                        Text(streamSnapshot.data!.docs[index]["dose_ml_Kg"].toString(),), //Ex: 40
                        Text(streamSnapshot.data!.docs[index]["dose_max"].toString(),),   //Ex: 1000

                      ],
                    ),
                  ),
                ),
              )
          );
        },
      ),

Here the result

Now, I want to do a operation with the data, like this:

    Text(streamSnapshot.data!.docs[index]["nome"].toString()),

       Text(streamSnapshot.data!.docs[index]["dose_ml_Kg"].toString(),),

  Text(streamSnapshot.data!.docs[index]["dose_max"].toString(),),
    
    _dose = streamSnapshot.data!.docs[index]["dose_ml_Kg"]*20, 

Text("$_dose"),

And the error is:

type 'int' is not a subtype of type 'Widget'

What's wrong where?

CodePudding user response：

You cant declare var inside children list what you have to do is

    StreamBuilder(
        stream: farmacos.orderBy("nome", descending: false).snapshots(),
        builder: (context, AsyncSnapshot<QuerySnapshot> streamSnapshot) {
          if (!streamSnapshot.hasData) {
            return const Text("No data...");
          }
_dose = streamSnapshot.data!.docs[index]["dose_ml_Kg"]*20,// //thats what you have to do
          return ListView.builder(
              itemCount: streamSnapshot.data!.docs.length,
              itemBuilder: (context, index) => GestureDetector(
                onTap: () {},
                child: Card(
                  color: Colors.amberAccent[100],
                  child: Padding(
                    padding: EdgeInsets.fromLTRB(_margem * .1,
                        _margem * .1, _margem * .1, _margem * .1),
                    child: Row(
                      crossAxisAlignment: CrossAxisAlignment.center,
                      mainAxisAlignment: MainAxisAlignment.spaceBetween,
                      children: [
    Text(streamSnapshot.data!.docs[index]["nome"].toString()),

       Text(streamSnapshot.data!.docs[index]["dose_ml_Kg"].toString(),),

  Text(streamSnapshot.data!.docs[index]["dose_max"].toString(),),
    
     

Text("$_dose"),

                      ],
                    ),
                  ),
                ),
              )
          );
        },
      ),