USB条码扫描器无需服务器调用即可重复扫描

问题描述

不确定我的用语是否正确。我知道我的代码也不有效。在这一点上寻找功能而不是效率。 （只是一位试图解决后勤问题的老师）。

我有一个网络应用程序，可用于将学生签入和签出图书馆。由于使用了COVID，因此我们尝试减少触摸键盘的次数，并加快签入过程。为此，我们有一台USB扫描仪，可以扫描学生证。

我的Webapp加载模板html，然后将名称等添加到不同的select元素。当学生签到时，该名称会出现在窗口的另一半，并等待他们单击其姓名旁边的签出。我相信这是在所谓的客户端完成的。

要添加条形码扫描仪，我添加了带有文本输入的表单元素。这是让条形码扫描仪与客户端交互的唯一方法吗？

<form><input type="text" id = "barcodeInput" size="1"></form>  

然后我有一些jQuery进行测试，以检查输入是否为条形码（按下了前缀和返回键），如果是，则将条形码中的学生ID编号放入循环中，以在select中找到匹配的ID。学生姓名的选项（id存储在值中，学生姓名存储在文本中）。此处也阻止了默认操作

所有这些都有效，我可以让一名学生添加到应用程序的“签入”面板中。

我无法让扫描仪在第二个学生上工作。我认为这与以下事实有关：我正在使用表单输入元素，并且可能需要服务器调用，但我不能这样做，因为我需要有越来越多的被检入图书馆的学生名单。

我借用了它，目前正在使用

$(document).ready(function() {
    var barcode=""; //sets my variable
    $(document).keydown(function(e) //looking to intercept the barcode scanner output
    {
        var code = (e.keyCode ? e.keyCode : e.which); //don't really know what this does since I borrowed this
        if(code==13&&(barcode.substring(1,5)=="SCAN"))// Enter key hit & from scanner
        {
            e.preventDefault(); //stops the enter key from actually "running" and stops the barcode from going into the input field (I think)
            barcode = barcode.slice(5);// remove the prefix so I am left with student number aka barcode
            alert(barcode); //lets me know I'm getting the correct student number
            processBarcode(barcode);        //sends to process barcode
        }
        else if(code==9)// Tab key hit    //I may not need these next 10ish lines
        {
            e.preventDefault();
            alert(barcode);      
        }
        else
        {
            e.preventDefault();
            barcode=barcode+String.fromCharCode(code);
        }
    });
});

这将在select元素中找到该学生，然后将select元素更改为读取该名称，并将该名称张贴在“谁正在签入”表格单元格中

function processBarcode(barcode){
     var name = "";
   $("#studentNameSelect option").each(function(){ //runs through the select element that has all student names...the name is in the parameter "text" and student ID # is in the parameter val
        if($(this).val()==barcode){ //looking to see if the student ID # matches the specific option in the select element
             name = $(this).text(); //figure out the student name based on ID #
             $(this).prop('selected',true); //set the select element to show this specific option
             $("#selectedName").html(name);  //puts student name in a table cell so they know they are picking the correct name
             //$("#barcodeInput").trigger("reset"); //here I'm trying to get the form element input to reset so I can use it again...this didn't work so its commented out
             $("#teacherNameSelect").focus(); //puts the focus onto the next select item so I can do other things
             return false; //breaks the each loop once student name has been found
        }
    }); 
}

然后这是将姓名移到“已签到”面板上的代码，以便下一位学生可以签入

function buildAttendanceRow(stringPackage){ //this function takes info from the selection panel and builds a table row in the "I'm at the library" panel. Students click check out when they leave the library
console.log(stringPackage);
    var package = JSON.parse(stringPackage); //receives a package of info from the selects,I do send this to a server function to email teachers that student arrived to the library...
console.log(package);
    var html = "";
    var hiddenId = new Date().getTime().toString(); //this cell is used to keep track of a specific instance of a student checked into the library so I can remove later and then mark in a backend spreadsheet database
    var nameCell = '<td class="package" id="'+hiddenId+'">'+package.student+'</td>';
    var checkOutButton = '<input type="button" value="Check Out" id="COButton">';
    var checkoutButtonCell = '<td class="center">'+checkOutButton+'</td>';
    html+="<tr>"+nameCell+checkoutButtonCell+"</tr>";
    $("#checkedInTable").append(html);   //puts the new table row into the checked in table
    $('#'+hiddenId).data("package",package); //stores info so I can remove table row and update database
    
    
    var lastTableRow = $('#checkedInTable tr:last');
    var button = lastTableRow.find('#COButton');
        //add the click function for removing row and sending checked out info to server for email and for database purposes
        button.click(function(e){
            var x = e.pageX;
            var y = e.pageY;
            var o = {
                left: x,top: y
            };
           $("#progressMonitor").show().offset(o);
            $(this).prop("disabled",true);
            var row = $(this).closest('tr');
            var carrierCell =$('#'+hiddenId); 
            var d = new Date();
            var payload = new Object(); //this object gets transferred to the server function,the user interface doesn't refresh here,it just has a dynamic html table built and shrunk as kids check in or check out
                payload.checkInTime = carrierCell.data("package").checkInTime;
                payload.timeIn = carrierCell.data("package").timeIn;
                payload.student = carrierCell.data("package").student;
                payload.teacherEmail = carrierCell.data("package").teacherEmail;
                payload.teacherName = carrierCell.data("package").teacherName;
                payload.reason = carrierCell.data("package").reason;
                payload.checkOutTime = d;
                payload.timeOut = d.getTime();
           var stringPayload = JSON.stringify(payload);
           row.hide();
           alternateRowColors($("#checkedInTable"));
           google.script.run.withSuccessHandler(emailAndRecordsSuccess).withFailureHandler(emailAndRecordsFailure).emailAndRecords(stringPayload);//calling the server function
        });
    
    var numRows =  $("#checkedInTable tr" ).length;
    if(numRows>2){
        alphaSortTable(); //puts the student names in alpha order so it is easier for them to checkout of the library
    }
    alternateRowColors($("#checkedInTable")); 
    $("#progressMonitor").hide();
    $("#barcodeInput").focus(); //here is me trying to get the scanner back into the input field so there is somewhere for the scanner data to go; I expected this to be all I needed to do,but at this point,even though the input is focused,the the scanner won't fire onto the document or into the field or anything like that
     alert($("#barcodeInput").val()); //this is telling me that there is no value in the input field at this point,I thought there might be info stored here screwing up the scanner

}

解决方法

解决方案是在完成客户端工作后将功能重新绑定到文档。 将其更改为命名函数：

$(document).ready(function() {
    var barcode=""; 
    $(document).keydown(function(e) 
    {
        var code = (e.keyCode ? e.keyCode : e.which); 
        if(code==13&&(barcode.substring(1,5)=="SCAN"))
        {
            e.preventDefault(); 
            barcode = barcode.slice(5);
            processBarcode(barcode); 
        }else if(code==9)// Tab key hit  
             {e.preventDefault();     
        }else{
            e.preventDefault();
            barcode=barcode+String.fromCharCode(code);
        }
    });
});

现在我有：

function getBarcode(){
var barcode=""; 
    $(document).keydown(function(e) 
    {
        var code = (e.keyCode ? e.keyCode : e.which); 
        if(code==13&&(barcode.substring(1,5)=="SCAN"))
        {
            e.preventDefault(); 
            barcode = barcode.slice(5);
            processBarcode(barcode); 
        }else if(code==9)// Tab key hit  
             {e.preventDefault();     
        }else{
            e.preventDefault();
            barcode=barcode+String.fromCharCode(code);
        }
    });

和

$(document).ready(function() {
     getBarcode();
}

我可以打电话

getBarcode();

在任何地方重新连接文档以查找条形码扫描仪。