flutter 中 toast 的封装

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import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';

class Toast {
  static OverlayEntry _overlayEntry; // toast靠它加到屏幕上
  static bool _showing = false; // toast是否正在showing
  static DateTime _startedTime; // 开启一个新toast的当前时间，用于对比是否已经展示了足够时间
  static String _msg; // 提示内容
  static int _showTime; // toast显示时间
  static Color _bgColor; // 背景颜色
  static Color _textColor; // 文本颜色
  static double _textSize; // 文字大小
  static String _toastPosition; // 显示位置
  static double _pdHorizontal; // 左右边距
  static double _pdVertical; // 上下边距
  static void toast(
    BuildContext context, {
    String msg,
    int showTime = 2000,
    Color bgColor = Colors.black,
    Color textColor = Colors.white,
    double textSize = 14.0,
    String position = 'center',
    double pdHorizontal = 20.0,
    double pdVertical = 10.0,
  }) async {
    assert(msg != null);
    _msg = msg;
    _startedTime = DateTime.now();
    _showTime = showTime;
    _bgColor = bgColor;
    _textColor = textColor;
    _textSize = textSize;
    _toastPosition = position;
    _pdHorizontal = pdHorizontal;
    _pdVertical = pdVertical;
    //获取OverlayState
    OverlayState overlayState = Overlay.of(context);
    _showing = true;
    if (_overlayEntry == null) {
      _overlayEntry = OverlayEntry(
          builder: (BuildContext context) => Positioned(
                //top值，可以改变这个值来改变toast在屏幕中的位置
                top: _calToastPosition(context),
                child: Container(
                    alignment: Alignment.center,
                    width: MediaQuery.of(context).size.width,
                    child: Padding(
                      padding: EdgeInsets.symmetric(horizontal: 40.0),
                      child: AnimatedOpacity(
                        opacity: _showing ? 1.0 : 0.0, //目标透明度
                        duration: _showing
                            ? Duration(milliseconds: 100)
                            : Duration(milliseconds: 400),
                        child: _buildToastWidget(),
                      ),
                    )),
              ));
      overlayState.insert(_overlayEntry);
    } else {
      //重新绘制UI，类似setState
      _overlayEntry.markNeedsBuild();
    }
    await Future.delayed(Duration(milliseconds: _showTime)); // 等待时间

    //2秒后 到底消失不消失
    if (DateTime.now().difference(_startedTime).inMilliseconds >= _showTime) {
      _showing = false;
      _overlayEntry.markNeedsBuild();
      await Future.delayed(Duration(milliseconds: 400));
      _overlayEntry.remove();
      _overlayEntry = null;
    }
  }

  //toast绘制
  static _buildToastWidget() {
    return Center(
      child: Card(
        color: _bgColor,
        child: Padding(
          padding: EdgeInsets.symmetric(
              horizontal: _pdHorizontal, vertical: _pdVertical),
          child: Text(
            _msg,
            style: TextStyle(
              fontSize: _textSize,
              color: _textColor,
            ),
          ),
        ),
      ),
    );
  }

//  设置toast位置
  static _calToastPosition(context) {
    var backResult;
    if (_toastPosition == 'top') {
      backResult = MediaQuery.of(context).size.height * 1 / 4;
    } else if (_toastPosition == 'center') {
      backResult = MediaQuery.of(context).size.height * 2 / 5;
    } else {
      backResult = MediaQuery.of(context).size.height * 3 / 4;
    }
    return backResult;
  }
}

调用：

1
Toast.toast(context, (msg: "吐司文案"));