模拟的时候摄像头可以调用，发布了以后就不行了

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各位大佬，请问一下为什么模拟的时候摄像头是可以调用的，但是发布了以后就不行了呢？

调用摄像头是用的页面加载时的JS命令

$("[fgcname=video]").empty();
$("[fgcname=video]").append("<video id='video' width='200' height='150'></video>");

$("[fgcname=canvas]").empty();
$("[fgcname=canvas]").append(" <canvas id='canvas' width='1280' height='720'></canvas>");

var video = document.getElementById('video'),
      canvas = document.getElementById('canvas'),
      img = document.getElementById('img'),
      vendorUrl = window.URL || window.webkitURL;


navigator.getMedia = navigator.getUserMedia ||
                     navagator.webkitGetUserMedia ||
                     navigator.mozGetUserMedia ||
                     navigator.msGetUserMedia;
navigator.getMedia({
      video: true,
      audio: false
}, function(strem){
      console.log(strem);
      //video.src = vendorUrl.createObjectURL(strem);
video.srcObject = strem;
      video.play();
}, function(error) {
      //error.code
      console.log(error);
});