Question

问题：我使用Cognex MX-1000扫描条形码。我有三个文本框，我正在尝试扫描条形码并将焦点更改为下一个文本框。但是在我扫描第三个文本框后，即使焦点位于第一个文本框，也始终在第三个文本框中输入值。

原因：我的代码无法退出最内层的Setresultcallback函数。以下是我的方法有谁知道如何退出最里面的回调函数？

 me.scanner.setResultCallback(function (result) {  //First callback
        var barcode = result.readString;
        var txt1 = barcode;
        document.getElementById("TextBox1").value = txt1;
        document.getElementById("TextBox2").focus();

        me.scanner.setResultCallback(function (result) {  //Second callback
            var barcode = result.readString;
            var txt2 = barcode;
            document.getElementById("TextBox2").value = txt2;
            document.getElementById("TextBox3").focus();

            me.scanner.setResultCallback(function (result) {   //Third Callback & stuck here!!! I want to exit this function
                var barcode = result.readString;
                var txt3 = barcode;
                document.getElementById("TextBox3").value = txt3;
                document.getElementById("TextBox1").focus();
                return;
            });
            return;
        });
        return;
    });

Answer 1

那是因为你在最后一个回调中留下第三个字段的回调。以下内容应解决问题。

me.scanner.setResultCallback(/* Change here -> */ function firstFieldCallback(result) {  //First callback
        var barcode = result.readString;
        var txt1 = barcode;
        document.getElementById("TextRec1").value = txt1;
        document.getElementById("TextRec2").focus();

        me.scanner.setResultCallback(function (result) {  //Second callback
            var barcode = result.readString;
            var txt2 = barcode;
            document.getElementById("TextRec2").value = txt2;
            document.getElementById("TextRec3").focus();

            me.scanner.setResultCallback(function (result) {   //Third Callback & stuck here!!! I want to exit this function
                var barcode = result.readString;
                var txt3 = barcode;
                document.getElementById("TextRec3").value = txt3;
                document.getElementById("TextRec1").focus();

                /* Change here -> */ me.scanner.setResultCallback(firstFieldCallback);                  

                return;
            });
            return;
        });
        return;
    });

Answer 2

问题在于您没有重新绑定到第一个回调。因为你总是在你的回调中做同样的事情：

获取值
将值写入当前输入
关注下一个输入

可以将其简化为：

var me = {
    scanner: {
      setResultCallback: function(callback) {
        setTimeout(function() {
          callback({
            readString: Math.floor(Math.random() * 100) + 1
          })
        }, 1000);
      }
    }
  },
  textboxes = ['TextRec1', 'TextRec2', 'TextRec3'],
  index = 0;

function readValue(result) {
  var barcode = result.readString;

  document.getElementById(textboxes[index++]).value = barcode;

  index = index === textboxes.length ? 0 : index;
  document.getElementById(textboxes[index]).focus();

  me.scanner.setResultCallback(readValue);
}

me.scanner.setResultCallback(readValue);

<input type="text" id="TextRec1" />
<input type="text" id="TextRec2" />
<input type="text" id="TextRec3" />

不介意var me = { ...我想要模仿你所描述的行为。

Answer 3

我已经制作了一个片段来演示如何做到这一点。每个函数都将回调设置为现有函数，而不是创建一个新函数来设置它。我让它与setInterval一起工作，这样你就可以看到更好的事情发生了什么。你可以看到每个新的扫描扫描都会覆盖下一个框，证明焦点在周围。

＆＃13;

//Code to make this work in a snippet
var me = {};
me.scanner={};
me.scanner.setResultCallback = function(newcallback){scancallback=newcallback;};

//Set the callback to the first function; each function sets it to the next
me.scanner.setResultCallback(scan1);

//Simulate scanning stuff by manually calling the callback with time intervals; just pretend each time the function is called, it's called naturally by scanning with the scanner
setInterval(function(){
  scancallback({randomField:"this is a scan result I guess",readString:Math.floor(Math.random()*10000)});
},1000);

function scan1(scanresult){
  //Don't even need the variables, if you need them somehow you can add them back
  document.getElementById("TextRec1").value = 
scanresult.readString;
  document.getElementById("TextRec2").focus();
  me.scanner.setResultCallback(scan2);
}

function scan2(scanresult){
  //Don't even need the variables, if you need them somehow you can add them back
  document.getElementById("TextRec2").value = 
scanresult.readString;
  document.getElementById("TextRec3").focus();
  me.scanner.setResultCallback(scan3);
}

function scan3(scanresult){
  //Don't even need the variables, if you need them somehow you can add them back
  document.getElementById("TextRec3").value = 
scanresult.readString;
  document.getElementById("TextRec1").focus();
  me.scanner.setResultCallback(scan1);
}

＆＃13;

<input type="text" id="TextRec1"/>
<input type="text" id="TextRec2"/>
<input type="text" id="TextRec3"/>

＆＃13;

在javascript中退出回调方法

3 个答案: