doc: 更新文档

Author: ArgoZhang

src/BootstrapBlazor.Server/Components/Samples/VideoDevices.razor

@@ -14,7 +14,7 @@ private IBluetooth? BluetoothService { get; set; }</Pre>
     <div class="row form-inline g-3">
         <div class="col-12">
             <Button Text="@Localizer["VideoDeviceRequestText"]" Icon="fa-solid fa-photo-film" OnClick="OnRequestDevice"></Button>
-            <Button Text="@Localizer["VideoDeviceOpenText"]" Icon="fa-solid fa-play" OnClick="OnOpenVideo" IsDisabled="_isOpen" class="ms-2"></Button>
+            <Button Text="@Localizer["VideoDeviceOpenText"]" Icon="fa-solid fa-play" OnClick="OnOpenVideo" IsDisabled="_isOpen || string.IsNullOrEmpty(_deviceId)" class="ms-2"></Button>
             <Button Text="@Localizer["VideoDeviceCloseText"]" Icon="fa-solid fa-stop" OnClick="OnCloseVideo" IsDisabled="!_isOpen" class="ms-2"></Button>
             <Button Text="@Localizer["VideoDeviceCaptureText"]" Icon="fa-solid fa-camera" OnClick="OnCapture" IsDisabled="!_isOpen" class="ms-2"></Button>
         </div>

src/BootstrapBlazor.Server/Components/Samples/VideoDevices.razor.cs

@@ -43,12 +43,13 @@ private async Task OnOpenVideo()
                 DeviceId = _deviceId,
                 VideoSelector = ".bb-video"
             };
-            _isOpen =  await VideoDeviceService.Open(constraints);
+            _isOpen = await VideoDeviceService.Open(constraints);
         }
     }
 
     private async Task OnCloseVideo()
     {
+        _isOpen = false;
         _previewUrl = "";
         await VideoDeviceService.Close(".bb-video");
     }