Question

我创建了一个 webview 应用程序，我可以在其中扫描 QR 码。在移动和桌面浏览器上一切正常，但在应用程序中我得到 Unable to access video stream (please make sure you have a webcam enabled)。

我正在分享下面的一些代码：

这是我用来扫描二维码的 HTML :

<div id="loadingMessage">
       Unable to access video stream (please make sure you have a webcam enabled)
</div>
<canvas id="canvas" hidden></canvas>
<div id="output" style="padding-right: 35px;padding-left: 35px;width: fit-content;">
  <div><b> QR Code Data:</b> <span id="outputData"></span></div>
</div>

还有 JS :

<script>

var video = document.createElement("video");
var canvasElement = document.getElementById("canvas");
var canvas = canvasElement.getContext("2d");
var loadingMessage = document.getElementById("loadingMessage");
var outputContainer = document.getElementById("output");
var outputData = document.getElementById("outputData");

function drawLine(begin, end, color) {
    canvas.beginPath();
    canvas.moveTo(begin.x, begin.y);
    canvas.lineTo(end.x, end.y);
    canvas.lineWidth = 4;
    canvas.strokeStyle = color;
    canvas.stroke();
}

navigator.mediaDevices.getUserMedia({ video: { facingMode: "user" } }).then(function (stream) {
    video.srcObject = stream;
    video.setAttribute("playsinline", true); 
    video.play();
    requestAnimationFrame(tick);
});

function tick() {
    loadingMessage.innerText = "⌛ Loading video..."
    if (video.readyState === video.HAVE_ENOUGH_DATA) {
        loadingMessage.hidden = true;
        canvasElement.hidden = false;
        outputContainer.hidden = false;

        canvasElement.height = video.videoHeight;
        canvasElement.width = video.videoWidth;
        canvas.drawImage(video, 0, 0, canvasElement.width, canvasElement.height);
        var imageData = canvas.getImageData(0, 0, canvasElement.width, canvasElement.height);
        var code = jsQR(imageData.data, imageData.width, imageData.height, {
            inversionAttempts: "dontInvert",
        });
        if (code) {
            drawLine(code.location.topLeftCorner, code.location.topRightCorner, "#FF3B58");
            drawLine(code.location.topRightCorner, code.location.bottomRightCorner, "#FF3B58");
            drawLine(code.location.bottomRightCorner, code.location.bottomLeftCorner, "#FF3B58");
            drawLine(code.location.bottomLeftCorner, code.location.topLeftCorner, "#FF3B58");
            outputData.innerText = code.data;
        }
    }
    requestAnimationFrame(tick);
}

</script>

我还请求在 MainActivity.cs 中在运行时授予相机访问权限。

这是与 Xamarin Webview 中的权限相关的代码：

class MyWebClient : WebChromeClient
{
    Activity mContext;

    
    public MyWebClient(Activity context)
    {
        this.mContext = context;
    }
    public override void OnPermissionRequest(PermissionRequest request)
    {
        mContext.RunOnUiThread(() => {
            request.Grant(request.GetResources());
        });
    }
}

我还在 Manifest 文件中使用了以下权限：

<uses-permission android:name="android.permission.CAMERA" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

我也尝试了 here 和 here 建议的解决方案，但对我不起作用。

Answer 1

添加 MediaPlaybackRequiresUserGesture = false 对我有用（用 webrtc 测试）。试试看。我添加了我的渲染器的一部分。 LMK，如果你需要它。

 protected override void OnElementChanged(ElementChangedEventArgs<Xamarin.Forms.WebView> e)
    {
        base.OnElementChanged(e);
        Control.Settings.JavaScriptEnabled = true;
        Control.Settings.MediaPlaybackRequiresUserGesture = false;
        Control.ClearCache(true);
        Control.SetWebChromeClient(new MyWebClient(mContext));
    }

授予 Xamarin Android Webview 相机权限但无访问权限

1 个答案: