在 nativescript-vue 应用程序中存储一个值

Question

我正在使用 nativescript-vue 制作一个简单的应用程序，在主页上我有一个启动扫描仪的按钮，因此我可以扫描产品。这是我的主页：

<template>
  <Page class="page">

   <StackLayout class="hello-world">
     <Button @tap="scan" text="Scan a product"/>
   </StackLayout>

  </Page>
</template>

<script>
const BarcodeScanner = require("nativescript- 
barcodescanner").BarcodeScanner;
import Display from "./Display";
export default {
data() {
  return {
    text: ""
  };
},
methods: {
scan: function() {
  var barcodescanner = new BarcodeScanner();
  barcodescanner
    .scan({
      // formats: "QR_CODE,PDF_417", // Pass in of you want to restrict scanning to certain types
      cancelLabel: "EXIT. Also, try the volume buttons!", // iOS only, default 'Close'
      cancelLabelBackgroundColor: "#333333", // iOS only, default '#000000' (black)
      message: "Use the volume buttons for extra light", // Android only, default is 'Place a barcode inside the viewfinder rectangle to scan it.'
      showFlipCameraButton: true, // default false
      preferFrontCamera: false, // default false
      showTorchButton: true, // default false
      beepOnScan: true, // Play or Suppress beep on scan (default true)
      torchOn: false, // launch with the flashlight on (default false)
      closeCallback: function() {
        console.log("Scanner closed");
      }, // invoked when the scanner was closed (success or abort)
      resultDisplayDuration: 500, // Android only, default 1500 (ms), set to 0 to disable echoing the scanned text
      // orientation: "landscape", // Android only, optionally lock the orientation to either "portrait" or "landscape"
      openSettingsIfPermissionWasPreviouslyDenied: true // On iOS you can send the user to the settings app if access was previously denied
    })
    .then(
      function(result) {
        console.log("Scan format : " + result.format);
        console.log("Scan text :   " + result.text);
        this.text = result.text;

      },
      function(error) {
        console.log("No scan: " + error);
      }
    );
  }
}
};
</script>

这里我遇到了一个问题，因为行 "this.text = result.text;" 不起作用，所以我不知道如何存储 result.text 值。

Answer 1

请在回调中使用箭头函数而不是普通函数。这是因为箭头函数没有将它自己的上下文绑定到 this。相反，箭头函数在词法上绑定它们的上下文，因此 this 实际上指的是原始上下文。

解决方案：

barcodescanner
    .scan({
        ...
        })
    .then(
      (result) => {
        console.log("Scan format : " + result.format);
        console.log("Scan text :   " + result.text);
        this.text = result.text;
      },
      (error) => {
        console.log("No scan: " + error);
      }
    );
  }

在 nativescript-vue 应用程序中存储一个值

store a value in nativescript-vue app

vuejs2

nativescript-vue