Flutter - How to dismiss the keyboard and add the text from the textfield to the screen and update the screen. Not able to do both simultaneously

Here is my code:

bottomNavigationBar: MessageSendButton(
                        messageController: _controller,
                        onPressed: (){
                          messageList.value = []..addAll(messageList.value)..add(
                            MessageModel(
                              id: 1,
                              message: _controller.text,
                              firstName: data.firstName,
                              lastName: data.lastName,
                              createdAt: "2019-04-12 14:22:57.358854000",
                            ),
                          );
                        
                          _controller.text = '';
                          _scrollController.position.maxScrollExtent;
                          // 
                        }
                      ),

I tried using FocusScope.of(context).unfocus();, SystemChannels.textInput.invokeMethod('TextInput.hide'); and

if (!currentFocus.hasPrimaryFocus && currentFocus.focusedChild != null) {
                            FocusManager.instance.primaryFocus!.unfocus();
                          }

But its not working in the sense that it removes the keyboard but I am not able to add to my existing SliverList and rebuild the screen. If I remove the code for dismissing the keypad, I can successfully add to my existing list and rebuild the screen.

The only info I am getting is /TextInputPlugin(19317): Changing the content within the the composing region may cause the input method to behave strangely, and is therefore discouraged. See https://github.com/flutter/flutter/issues/78827 for more details I went to that link but wasn't able to infer much.

P.S. I am also not able to scroll to the bottom with my scrollController, _scrollController.position.maxScrollExtent; It just doesn't works.