Question

您好我正在制作一个使用Google Chrome打开我的Android相机的程序。当用户按下后退按钮时，我需要知道如何完全关闭镀铬，否则在镀铬时禁用后退按钮。这是我的代码。我想用JavaScript做。

<body style="overflow: hidden">
<video muted autoplay id="myvideo" style="width: 100%; height: auto"></video>
<div class='select'>
    <select style="visibility: hidden" id='videoSource'>
    </select>
</div>
</body>
<script type="text/javascript">

//Camera
var videoElement = document.querySelector("video");
var videoSelect = document.querySelector("select#videoSource");
navigator.getUserMedia = navigator.getUserMedia ||
navigator.webkitGetUserMedia || navigator.mozGetUserMedia;

//Checks for the sources available of cameras
function gotSources(sourceInfos) {
    for (var i = 0; i != sourceInfos.length; ++i) {
        var sourceInfo = sourceInfos[i];
        var option = document.createElement("option");
        option.value = sourceInfo.id;
        if (sourceInfo.kind === 'video') {
            option.text = sourceInfo.label || 'camera ' + (videoSelect.length + 1);
            videoSelect.appendChild(option);
            if (i == sourceInfos.length - 1) {
                option.selected = true;
                start();

            }
        } else {
            console.log('Some other kind of source: ', sourceInfo);
        }
    }
}

if (typeof MediaStreamTrack === 'undefined') {
    alert('This browser does not support MediaStreamTrack.\n\nTry Chrome Canary.');
} else {
    MediaStreamTrack.getSources(gotSources);
}

//Checks if everything is successful
function successCallback(stream) {
    window.stream = stream; // make stream available to console
    videoElement.src = window.URL.createObjectURL(stream);
    videoElement.play();
}

//Checks if an error occurred
function errorCallback(error) {
    console.log("navigator.getUserMedia error: ", error);
}


// starts the streaming of the camera
function start() {
    if (!!window.stream) {
        videoElement.src = null;
        window.stream.stop();
    }

    var videoSource = videoSelect.value;

    var constraints = {
        video: {
            optional: [{ sourceId: videoSource}]
        }
    };
    navigator.getUserMedia(constraints, successCallback, errorCallback);
}


videoSelect.onchange = start;

禁用后退按钮或设置后退按钮以关闭Android上的应用程序

0 个答案: