Toast.dart
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import 'package:flutter/material.dart';
///
/// @author tsing
/// @time 2018/10/15 下午2:33
/// @email shuqing.li@merculet.io
///
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;
static void toast(
BuildContext context,
String msg,
) async {
assert(msg != null);
_msg = msg;
_startedTime = DateTime.now();
//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: MediaQuery.of(context).size.height * 2 / 3,
child: Container(
alignment: Alignment.center,
width: MediaQuery.of(context).size.width,
child: Padding(
padding: EdgeInsets.symmetric(horizontal: 80.0),
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: 2000)); //等待两秒
//2秒后 到底消失不消失
if (DateTime.now().difference(_startedTime).inMilliseconds >= 2000) {
_showing = false;
_overlayEntry.markNeedsBuild();
}
}
//toast绘制
static _buildToastWidget() {
return Center(
child: Card(
color: Colors.black26,
child: Padding(
padding: EdgeInsets.symmetric(horizontal: 10.0, vertical: 5.0),
child: Text(
_msg,
style: TextStyle(
fontSize: 14.0,
color: Colors.white,
),
),
),
),
);
}
}