开发中有很多时候需要自定义一个组件使用中通过传入不同的参数来改变组件样式和状态本文将以自定义一个搜索框为例子本文抱砖引玉主要提供的自定义组件的思路具体的ui实现会有详细的文章进行说明

import 'package:flutter/material.dart';

enum SearchBarType { home, normal, homeLight }

class SearchBar extends StatefulWidget {
  final bool enabled;
  final bool hideLeft;
  final SearchBarType searchBarType;
  final String hint;
  final String defaultText;
  final void Function() leftButtonClick;
  final void Function() rightButtonClick;
  final void Function() speakClick;
  final void Function() inputBoxClick;
  final ValueChanged<String> onChanged;

  const SearchBar(
      {Key key,
        this.enabled = true,
        this.hideLeft,
        this.searchBarType = SearchBarType.normal,
        this.hint,
        this.defaultText,
        this.leftButtonClick,
        this.rightButtonClick,
        this.speakClick,
        this.inputBoxClick,
        this.onChanged})
      : super(key: key);

  @override
  _SearchBarState createState() => _SearchBarState();
}

class _SearchBarState extends State<SearchBar> {
  bool showClear = false;
  final TextEditingController _controller = TextEditingController();

  @override
  void initState() {
    if (widget.defaultText != null) {
      setState(() {
        _controller.text = widget.defaultText;
      });
    }
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    return widget.searchBarType == SearchBarType.normal
        ? _genNormalSearch()
        : _genHomeSearch();
  }

  _genNormalSearch() {
    return Container(
      child: Row(children: <Widget>[
        _wrapTap(
            Container(
              padding: EdgeInsets.fromLTRB(6, 5, 10, 5),
              child: widget?.hideLeft ?? false
                  ? null
                  : Icon(
                Icons.arrow_back_ios,
                color: Colors.grey,
                size: 26,
              ),
            ),
            widget.leftButtonClick),
        Expanded(
          flex: 1,
          child: _inputBox(),
        ),
        _wrapTap(
            Container(
              padding: EdgeInsets.fromLTRB(10, 5, 10, 5),
              child: Text(
                '搜索',
                style: TextStyle(color: Colors.blue, fontSize: 17),
              ),
            ),
            widget.rightButtonClick)
      ]),
    );
  }
  _genHomeSearch() {
    return Container(
      child: Row(children: <Widget>[
        _wrapTap(
            Container(
                padding: EdgeInsets.fromLTRB(6, 5, 5, 5),
                child: Row(
                  children: <Widget>[
                    Text(
                      '上海',
                      style: TextStyle(color: _homeFontColor(), fontSize: 14),
                    ),
                    Icon(
                      Icons.expand_more,
                      color: _homeFontColor(),
                      size: 22,
                    )
                  ],
                )),
            widget.leftButtonClick),
        Expanded(
          flex: 1,
          child: _inputBox(),
        ),
        _wrapTap(
            Container(
              padding: EdgeInsets.fromLTRB(10, 5, 10, 5),
              child: Icon(
                Icons.comment,
                color: _homeFontColor(),
                size: 26,
              ),
            ),
            widget.rightButtonClick)
      ]),
    );
  }

  _inputBox() {
    Color inputBoxColor;
    if (widget.searchBarType == SearchBarType.home) {
      inputBoxColor = Colors.white;
    } else {
      inputBoxColor = Color(int.parse('0xffEDEDED'));
    }
    return Container(
      height: 30,
      padding: EdgeInsets.fromLTRB(10, 0, 10, 0),
      decoration: BoxDecoration(
          color: inputBoxColor,
          borderRadius: BorderRadius.circular(
              widget.searchBarType == SearchBarType.normal ? 5 : 15)),
      child: Row(
        children: <Widget>[
          Icon(
            Icons.search,
            size: 20,
            color: widget.searchBarType == SearchBarType.normal
                ? Color(0xffA9A9A9)
                : Colors.blue,
          ),
          Expanded(
              flex: 1,
              child: widget.searchBarType == SearchBarType.normal
                  ? TextField(
                  controller: _controller,
                  onChanged: _onChanged,
                  autofocus: true,
                  style: TextStyle(
                      fontSize: 18.0,
                      color: Colors.black,
                      fontWeight: FontWeight.w300),
                  //输入文本的样式
                  decoration: InputDecoration(
                    contentPadding: EdgeInsets.fromLTRB(5, 0, 5, 0),
                    border: InputBorder.none,
                    hintText: widget.hint ?? '',
                    hintStyle: TextStyle(fontSize: 15),
                  ))
                  : _wrapTap(
                  Container(
                    child: Text(
                      widget.defaultText,
                      style: TextStyle(fontSize: 13, color: Colors.grey),
                    ),
                  ),
                  widget.inputBoxClick)),
          !showClear
              ? _wrapTap(
              Icon(
                Icons.mic,
                size: 22,
                color: widget.searchBarType == SearchBarType.normal
                    ? Colors.blue
                    : Colors.grey,
              ),
              widget.speakClick)
              : _wrapTap(
              Icon(
                Icons.clear,
                size: 22,
                color: Colors.grey,
              ), () {
            setState(() {
              _controller.clear();
            });
            _onChanged('');
          })
        ],
      ),
    );
  }

  _wrapTap(Widget child, void Function() callback) {
    return GestureDetector(
      onTap: () {
        if (callback != null) callback();
      },
      child: child,
    );
  }

  _onChanged(String text) {
    if (text.length > 0) {
      setState(() {
        showClear = true;
      });
    } else {
      setState(() {
        showClear = false;
      });
    }
    if (widget.onChanged != null) {
      widget.onChanged(text);
    }
  }

  _homeFontColor() {
    return widget.searchBarType == SearchBarType.homeLight
        ? Colors.black54
        : Colors.white;
  }
}

自定义完成后在界面中调用

@override
  Widget build(BuildContext context) {
    print('build');
    return Container(child: Column(children: <Widget>[RaisedButton(onPressed: (){
      setState(() {
        print('!!!!!!');
      });

    },),
      //此处引用自定义的组件
      SearchBar(
      hideLeft: true,
      defaultText: '自定义',
      searchBarType: SearchBarType.normal,
    )],),);
  }