当我尝试清理 stream 时，在 null 上调用了方法“map”

Question

I have a stream which feeds a list of items typed as 'Client'. I have too a search bar which the user writes some name and the list should filter the results as searched and when Click at other button named 'clear' it should reset the list to default. So, I have wrote these methods:

//called when tap search button (if it has a text typed)
  void setSearch(String search) {
    _search = search;
    _streamController.add(null);//the error throws here
    load(clean: true);
  }

//called when tap 'clear' button
  void clearSearch() {
    _search = '';
    _offset = 1;
    _clients.clear();
    _streamController.stream.drain();
    _streamController.add(null); //the error throws here
    load(clean: true);
  }

But when I tap search or clear it throws this error:

Receiver: null. NoSuchMethodError: The method 'map' was called on null. Tried calling: map(Closure: (Map<dynamic, dynamic>) => Client)

How can I handle this? there is another way to clean the stream? If you need more code I can update the question

UPDATE This is my build method

Scaffold(
      appBar: appBar(),
      body: Column(
        children: [
          Container(
            padding: EdgeInsets.all(5.0),
            width: MediaQuery.of(context).size.width,
            height: 60.0,
            child: Card(
              elevation: 3,
              child: Container(
                child: TextField(
                  style: TextStyle(
                    color: AppColorSecondary,
                  ),
                  cursorColor: Theme.of(context).primaryColor,
                  textInputAction: TextInputAction.search,
                  decoration: InputDecoration(
                    prefixIcon: Icon(Icons.search, color: AppColorSecondary,),
                    hintStyle: TextStyle(color: AppColorSecondary),
                    filled: true,
                    fillColor: AppColorPrimary,
                    border: OutlineInputBorder(),
                    focusedBorder: OutlineInputBorder(),
                    suffixIcon: GestureDetector(
                      onTap: (){
                        searchController.clear();
                        clientsController.loadMore();
                      },
                      child: FittedBox(
                        alignment: Alignment.center,
                        fit: BoxFit.fitHeight,
                        child: IconTheme(
                          data: IconThemeData(),
                          child: Icon(
                            Icons.clear,
                            color: Colors.black,
                          ),
                        ),
                      ),
                    ),
                  ),
                  controller: searchController,
                  onSubmitted: (value) {
                    clientsController.setSearch(searchController.text);
                  },
                ),
              ),
            ),
          ),
          Expanded(
            child: StreamBuilder(
              stream: clientsController.stream,
              builder: (ctx, snapshot) {
                if (snapshot.error != null) {
                  print(snapshot.error.toString());
                  return Center(
                    child: Text(snapshot.error.toString()),
                  );
                } else if (!snapshot.hasData) {
                  return Center(
                    child: CircularProgressIndicator(),
                  );
                } else if (snapshot.data.length == 0) {
                  return Center(
                    child: Text('0clients'),
                  );
                } else {
                  return RefreshIndicator(
                    onRefresh: clientsController.refresh,
                    child: ListView.builder(
                      controller: scrollController,
                      itemCount: snapshot.data.length + 1,
                      itemBuilder: (ctx, i) {
                        if (i < snapshot.data.length) {
                          return ClientsWidget(snapshot.data[i]);
                        } else if (clientsController.hasMore) {
                          return Padding(
                            padding: EdgeInsets.symmetric(vertical: 32.0),
                            child: Center(child: CircularProgressIndicator()),
                          );
                        } else {
                          return SizedBox(
                            height: 30,
                          );
                        }
                      },
                    ),
                  );
                }
              },
            ),
          )
        ],
      ),
    );
  }

Answer 1

Try _streamController.add([]);