flutter：实现扫码枪获取数据

近期使用Flutter开发了一个Windows项目，不使用TextField等控件，获取扫码枪返回的数据。

翻文档，发现官方提供了RawKeyboard 添加全局监听方法，既然找到方法了，开始愉快的编码吧。

编码完成，测试发现，在中文输入法启动的时候，RawKeyboard提供的监听不能正常回调，这是为啥呢？翻源码吧，终于，在RawKeyboard的handleRawKeyEvent方法里发现了罪魁祸首

这条路行不通了，走其他的路吧。

继续翻文档，发现Flutter提供了Focus控件，可以获取焦点，中文输入状态仍然可以正常执行回调方法。

改造一下，就可以用啦。

import 'dart:async';import 'package:flutter/material.dart';
import 'package:flutter/services.dart';import '../util/logger.dart';final _stringBuffer = StringBuffer();class ScanMonitor extends StatelessWidget {///final Widget child;///final ValueChanged<String>? onScanEnd;ScanMonitor({Key? key, required this.child, this.onScanEnd}): super(key: key);Timer? _timer;@overrideWidget build(BuildContext context) {return Focus(autofocus: true,canRequestFocus: true,child: child,onKey: (node, event) {if (event is RawKeyDownEvent) {_analysisKeyEvent(event);}return KeyEventResult.ignored;},);}///void _analysisKeyEvent(RawKeyDownEvent event) {String? str;/* 键盘第一行 */// ~ `if (PhysicalKeyboardKey.backquote == event.physicalKey) {str = event.isShiftPressed ? '~' : '`';}// 1 !if (PhysicalKeyboardKey.digit1 == event.physicalKey) {str = event.isShiftPressed ? '!' : '1';}// 2 @else if (PhysicalKeyboardKey.digit2 == event.physicalKey) {str = event.isShiftPressed ? '@' : '2';}// 3 #else if (PhysicalKeyboardKey.digit3 == event.physicalKey) {str = event.isShiftPressed ? '#' : '3';}// 4 $else if (PhysicalKeyboardKey.digit4 == event.physicalKey) {str = event.isShiftPressed ? r'$' : '4';}// 5 %else if (PhysicalKeyboardKey.digit5 == event.physicalKey) {str = event.isShiftPressed ? '%' : '5';}// 6 ^else if (PhysicalKeyboardKey.digit6 == event.physicalKey) {str = event.isShiftPressed ? '^' : '6';}// 7 &else if (PhysicalKeyboardKey.digit7 == event.physicalKey) {str = event.isShiftPressed ? '&' : '7';}// 8 *else if (PhysicalKeyboardKey.digit8 == event.physicalKey) {str = event.isShiftPressed ? '*' : '8';}// 9 (else if (PhysicalKeyboardKey.digit9 == event.physicalKey) {str = event.isShiftPressed ? '(' : '9';}// 0 )else if (PhysicalKeyboardKey.digit0 == event.physicalKey) {str = event.isShiftPressed ? ')' : '0';}// - _else if (PhysicalKeyboardKey.minus == event.physicalKey) {str = event.isShiftPressed ? '_' : '-';}// = +else if (PhysicalKeyboardKey.equal == event.physicalKey) {str = event.isShiftPressed ? '+' : '=';}/* 键盘第二行 */// Q qelse if (PhysicalKeyboardKey.keyQ == event.physicalKey) {str = event.isShiftPressed ? 'Q' : 'q';}// W welse if (PhysicalKeyboardKey.keyW == event.physicalKey) {str = event.isShiftPressed ? 'W' : 'w';}// E eelse if (PhysicalKeyboardKey.keyE == event.physicalKey) {str = event.isShiftPressed ? 'E' : 'e';}// R relse if (PhysicalKeyboardKey.keyR == event.physicalKey) {str = event.isShiftPressed ? 'R' : 'r';}// T telse if (PhysicalKeyboardKey.keyT == event.physicalKey) {str = event.isShiftPressed ? 'T' : 't';}// Y yelse if (PhysicalKeyboardKey.keyY == event.physicalKey) {str = event.isShiftPressed ? 'Y' : 'y';}// U uelse if (PhysicalKeyboardKey.keyU == event.physicalKey) {str = event.isShiftPressed ? 'U' : 'u';}// I ielse if (PhysicalKeyboardKey.keyI == event.physicalKey) {str = event.isShiftPressed ? 'I' : 'i';}// O oelse if (PhysicalKeyboardKey.keyO == event.physicalKey) {str = event.isShiftPressed ? 'O' : 'o';}// P pelse if (PhysicalKeyboardKey.keyP == event.physicalKey) {str = event.isShiftPressed ? 'P' : 'p';}// { [else if (PhysicalKeyboardKey.bracketLeft == event.physicalKey) {str = event.isShiftPressed ? '{' : '[';}// } ]else if (PhysicalKeyboardKey.bracketRight == event.physicalKey) {str = event.isShiftPressed ? '}' : ']';}// | \else if (PhysicalKeyboardKey.backslash == event.physicalKey) {str = event.isShiftPressed ? '|' : r'\';}/* 键盘第三行 */// A aelse if (PhysicalKeyboardKey.keyA == event.physicalKey) {str = event.isShiftPressed ? 'A' : 'a';}// S selse if (PhysicalKeyboardKey.keyS == event.physicalKey) {str = event.isShiftPressed ? 'S' : 's';}// D delse if (PhysicalKeyboardKey.keyD == event.physicalKey) {str = event.isShiftPressed ? 'D' : 'd';}// F felse if (PhysicalKeyboardKey.keyF == event.physicalKey) {str = event.isShiftPressed ? 'F' : 'f';}// G gelse if (PhysicalKeyboardKey.keyG == event.physicalKey) {str = event.isShiftPressed ? 'G' : 'g';}// H helse if (PhysicalKeyboardKey.keyH == event.physicalKey) {str = event.isShiftPressed ? 'H' : 'h';}// J jelse if (PhysicalKeyboardKey.keyJ == event.physicalKey) {str = event.isShiftPressed ? 'J' : 'j';}// K kelse if (PhysicalKeyboardKey.keyK == event.physicalKey) {str = event.isShiftPressed ? 'K' : 'k';}// L lelse if (PhysicalKeyboardKey.keyL == event.physicalKey) {str = event.isShiftPressed ? 'L' : 'l';}// : ;else if (PhysicalKeyboardKey.semicolon == event.physicalKey) {str = event.isShiftPressed ? ':' : ';';}// " 'else if (PhysicalKeyboardKey.quote == event.physicalKey) {str = event.isShiftPressed ? '"' : '\'';}/* 键盘第四行 */// Z zelse if (PhysicalKeyboardKey.keyZ == event.physicalKey) {str = event.isShiftPressed ? 'Z' : 'z';}// X xelse if (PhysicalKeyboardKey.keyX == event.physicalKey) {str = event.isShiftPressed ? 'X' : 'x';}// C celse if (PhysicalKeyboardKey.keyC == event.physicalKey) {str = event.isShiftPressed ? 'C' : 'c';}// V velse if (PhysicalKeyboardKey.keyV == event.physicalKey) {str = event.isShiftPressed ? 'V' : 'v';}// B belse if (PhysicalKeyboardKey.keyB == event.physicalKey) {str = event.isShiftPressed ? 'B' : 'b';}// N nelse if (PhysicalKeyboardKey.keyN == event.physicalKey) {str = event.isShiftPressed ? 'N' : 'n';}// M melse if (PhysicalKeyboardKey.keyM == event.physicalKey) {str = event.isShiftPressed ? 'M' : 'm';}// < ,else if (PhysicalKeyboardKey.comma == event.physicalKey) {str = event.isShiftPressed ? '<' : ',';}// > .else if (PhysicalKeyboardKey.period == event.physicalKey) {str = event.isShiftPressed ? '>' : '.';}// ? /else if (PhysicalKeyboardKey.slash == event.physicalKey) {str = event.isShiftPressed ? '?' : '/';}/* 键盘第五行 */// 空格else if (PhysicalKeyboardKey.space == event.physicalKey) {str = ' ';}/* 小键盘 */// 0else if (PhysicalKeyboardKey.numpad0 == event.physicalKey) {str = '0';}// 1else if (PhysicalKeyboardKey.numpad1 == event.physicalKey) {str = '1';}// 2else if (PhysicalKeyboardKey.numpad2 == event.physicalKey) {str = '2';}// 3else if (PhysicalKeyboardKey.numpad3 == event.physicalKey) {str = '3';}// 4else if (PhysicalKeyboardKey.numpad4 == event.physicalKey) {str = '4';}// 5else if (PhysicalKeyboardKey.numpad5 == event.physicalKey) {str = '5';}// 6else if (PhysicalKeyboardKey.numpad6 == event.physicalKey) {str = '6';}// 7else if (PhysicalKeyboardKey.numpad7 == event.physicalKey) {str = '7';}// 8else if (PhysicalKeyboardKey.numpad8 == event.physicalKey) {str = '8';}// 9else if (PhysicalKeyboardKey.numpad9 == event.physicalKey) {str = '9';}// +else if (PhysicalKeyboardKey.numpadAdd == event.physicalKey) {str = '+';}// -else if (PhysicalKeyboardKey.numpadSubtract == event.physicalKey) {str = '-';}// *else if (PhysicalKeyboardKey.numpadMultiply == event.physicalKey) {str = '*';}// /else if (PhysicalKeyboardKey.numpadDivide == event.physicalKey) {str = '/';}// .else if (PhysicalKeyboardKey.numpadDecimal == event.physicalKey) {str = '.';}// 处理结果if (str != null && str.isNotEmpty) {_stringBuffer.write(str);}if (LogicalKeyboardKey.enter == event.logicalKey) {_timer = _buildTimber();} else {_timer = _buildTimber(milliseconds: 500);}}/// 生成计时器Timer _buildTimber({int milliseconds = 500}) {// 取消定时器_timer?.cancel();_timer = null;// 创建新的定时器对象return Timer(Duration(milliseconds: milliseconds), () {// 解析数据String result = _stringBuffer.toString();_stringBuffer.clear();if (result.isNotEmpty) {logger.d(result);onScanEnd?.call(result);}});}
}

将ScanMonitor作为父节点，嵌套自己的页面作为子类。在onScanEnd方法里处理收到的数据。

@overrideWidget build(BuildContext context) {return Scaffold(body: ScanMonitor(onScanEnd: (value) {print('扫描结果：$value');},child: Stack(children: [],),),);}

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