Question

尝试将Instascan QR码扫描仪连接到AR.js。一切正常，但手机上的前置摄像头已打开，将其切换回后置摄像头无效。库分别与后置摄像头配合使用，并允许您进行切换，并且只有第一个打开。 Chrome浏览器不允许您在打开页面时选择相机，因此问题主要与他有关。

代码示例： Codepen，MediaTrackSettings

<html>
  <head>
    <script src="https://rawgit.com/schmich/instascan-builds/master/instascan.min.js"></script>
    <script src="https://aframe.io/releases/1.0.3/aframe.min.js"></script>
    <script src="https://raw.githack.com/jeromeetienne/AR.js/2.2.2/aframe/build/aframe-ar.js"></script> 
  </head>
  <body>
    <a-scene>
        <a-entity camera></a-entity>
    </a-scene>
 </body>
</html>

// Instascan QR scanner
let scanner = new Instascan.Scanner(
  {
    video: document.getElementById('arjs-video')
  }
);
scanner.addListener('scan', function(content) {
  alert('Content: ' + content);
  window.open(content, "_blank");
});

// Instascan camera switch
Instascan.Camera.getCameras().then(function (cameras) {
  if (cameras.length > 1) {
    scanner.start(cameras[cameras.length - 1]);
  } else {
    scanner.start(cameras[0]);
  }
}).catch(function (e) {
  console.error(e);
});

// MediaTrackSettings
let supports = navigator.mediaDevices.getSupportedConstraints();
if (supports["facingMode"]) {
    alert('Not Support!');
} else {
  let constraints = {
    facingMode: { exact: "environment" }
};
myTrack.applyConstraints(constraints);

Answer 1

这对我有用。我在 Microsoft Surface 和 Android 手机上对此进行了测试。

        //Detect user's cameras
        Instascan.Camera.getCameras().then(function (cameras) {
            //If a camera is detected
            if (cameras.length > 0) {
                //If the user has a rear/back camera
                if (cameras[1]) {
                    //use that by default
                    scanner.start(cameras[1]);
                } else {
                    //else use front camera
                    scanner.start(cameras[0]);
                }
            } else {
                //if no cameras are detected give error
                console.error('No cameras found.');
            }
        }).catch(function (e) {
            console.error(e);
        });

我没有包含 MediaTrackSettings，也没有任何问题。

强制在移动设备上使用后置摄像头？

1 个答案: