自定义TextField，加减数量输入框，可以根据自己的需求任意改动 先看效果

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实现方式 为一行 ，左边一个按钮右边一个按钮 中间一个 TextField 很简单

import 'package:flutter/material.dart';
//faith 2020年04月20日11:05:57
class NumberControllerWidget extends StatefulWidget {
  //高度
 final double height;
 //输入框的宽度 总体宽度为自适应
 final double width;
 //按钮的宽度
 final double iconWidth;
 //默认输入框显示的数量
 final String numText;
 //点击加号回调 数量
 final ValueChanged addValueChanged;
 //点击减号回调 数量
 final ValueChanged removeValueChanged;
 //点击减号任意一个回调 数量
 final ValueChanged updateValueChanged;

 NumberControllerWidget({
   this.height = 30,
   this.width = 40,
   this.iconWidth = 40,
   this.numText = '0',
   this.addValueChanged,
   this.removeValueChanged,
   this.updateValueChanged,
 });
  @override
  _NumberControllerWidgetState createState() => _NumberControllerWidgetState();
}

class _NumberControllerWidgetState extends State<NumberControllerWidget> {
  var textController= new TextEditingController();

  @override
  void initState() {
    // TODO: implement initState
    super.initState();
    this.textController.text = widget.numText;
  }

  @override
  Widget build(BuildContext context) {
    return Row(
      children: <Widget>[
        Container(
          height: widget.height,
          decoration: BoxDecoration(
              borderRadius: BorderRadius.circular(4),
              border: Border.all(width: 1,color: Colors.black12)
          ),
          child: Row(
            mainAxisSize: MainAxisSize.min,
            children: <Widget>[
              //减号
              CoustomIconButton(icon: Icons.remove,isAdd: false),
              //输入框
              Container(
                width: widget.width,
                decoration: BoxDecoration(
                    border: Border(
                      left: BorderSide(width: 1,color: Colors.black12),
                        right: BorderSide(width: 1,color: Colors.black12)
                    )
                ),
                child: TextField(
                  controller: textController,
                  keyboardType: TextInputType.number,
                  textAlign: TextAlign.center,
                  style: TextStyle(
                    fontSize: 12
                  ),
                  enableInteractiveSelection: false,
                  decoration: InputDecoration(
                    contentPadding: EdgeInsets.only(left: 0,top: 2,bottom: 2,right: 0),
                    border: const OutlineInputBorder(
                      gapPadding: 0,
                      borderSide: BorderSide(
                        width: 0,
                        style: BorderStyle.none,
                      ),
                    ),
                  ),
                ),
              ),
              //加号
              CoustomIconButton(icon: Icons.add,isAdd: true),
            ],
          ),
        )
      ],
    );
  }

 Widget CoustomIconButton({IconData icon,bool isAdd}){
    return Container(
      width: widget.iconWidth,
      child:IconButton(
        padding: EdgeInsets.all(0),
        icon: Icon(icon),
        onPressed: (){
          var num = int.parse(textController.text);
          if(!isAdd&&num ==0)return;
          if(isAdd){
            num ++;
            if(widget.addValueChanged !=null)widget.addValueChanged(num);
          }
          else{
            num --;
            if(widget.removeValueChanged !=null)widget.removeValueChanged(num);
          }
          textController.text = '$num';
          if(widget.updateValueChanged !=null)widget.updateValueChanged(num);
        },
      ),
    );
  }
}

使用

 NumberControllerWidget(
              numText: '0',
              addValueChanged: (num){
                print(num);
              },
              removeValueChanged: (num){
                print(num);

              },
              updateValueChanged: (num){

              },
            )

键盘结束响应 可以在最外面包一层GestureDetector

   onTap: (){
            FocusScope.of(context).requestFocus(FocusNode());
          },