这个方法我发现不止我一个人调用没生效- -

这里提供个暂时方案

因为注销不掉nfc监听事件，只好确保整个生命周期内仅有一个nfc监听事件，所以全局定义：

1.一个变量nfcState（用于判断监听事件是否开启

2.一个方法（通过route事件去调用页面的scanNfc()，具体逻辑写在scanNfc内

nfcInit() {
			
			if (!this.state.nfc) {
				this.state.nfc = wx.getNFCAdapter();
			}
  
  			let ab2str = (buffer) => {//转码
  				let dataView = new DataView(buffer);
  				let str = '';
  				for (let i = 0; i < dataView.byteLength; i++) {
					let num16 = dataView.getUint8(i);
					if (num16 / 16 >= 10) {
						str += String.fromCharCode(65 + parseInt(num16 / 16) - 10);
					} else {
						str += String.fromCharCode(48 + parseInt(num16 / 16));
					}
					if (num16 % 16 >= 10) {
						str += String.fromCharCode(65 + parseInt(num16 % 16) - 10);
					} else {
						str += String.fromCharCode(48 + parseInt(num16 % 16));
					}
				}
				return str;
			};
			let errCode = {
				13000: '本设备不支持NFC',
				13001: '系统NFC开关未打开',
				13010: '未知错误',
				13019: '用户未授权',
				13021: '已经开始NFC扫描',
				13018: '尝试在未开始NFC扫描时停止NFC扫描',
				13022: '标签已经连接',
				13023: '尝试在未连接标签时断开连接',
				13013: '未扫描到NFC标签',
				13014: '无效的标签技术',
				13015: '从标签上获取对应技术失败',
				13024: '当前标签技术不支持该功能',
				13017: '相关读写操作失败',
				13016: '连接失败',
			}
			if (!this.state.nfcState) {
				this.state.nfc.startDiscovery({
					success: res => {
						this.state.nfcState = true;
						this.state.nfc.onDiscovered(res => {
							console.log('nfc回调', res);
							let code = ab2str(res.id);
							// this.$msg('扫描成功！');
							let routes = getCurrentPages();
							// console.log(routes[routes.length-1].$vm.testNfc)
							if (routes[routes.length - 1].$vm.scanNfc) {
								routes[routes.length - 1].$vm.scanNfc(code)
							}
						});
					},
					fail: err => {
						console.log('failed to discover:', err);
						let content = errCode[err.errCode];
						wx.showModal({
							title: '错误',
							showCancel: false,
							content,
							success: function(res) {
								if (res.confirm) {
									console.log('用户点击确定');
									let routes = getCurrentPages();
									// console.log(routes[routes.length-1].$vm.testNfc)
									if (routes[routes.length - 1].$vm.openNfcFail) {
										routes[routes.length - 1].$vm.openNfcFail()
									}
								}
							}
						});
					}
				});
			}

		}