How to “set” a selected camera with combobox in Windows 10 Universal App

问题

I am developing windows application.I want to switch from Front Camera to Back Camera with a Combobox in Windows Universal App or in WPF.

I have coded something but I don't get where I made a mistake.

Here is my code:

<ComboBox  x:Name="SettingsCamera"  HorizontalAlignment="Stretch" Grid.Row="1" Grid.Column="0" Margin="0,5" SelectionChanged="SettingsCamera_SelectionChanged"/>

private async void InitializeCameraAsync()
        {DeviceInformation device = FindCameraDeviceByPanelAsync(Windows.Devices.Enumeration.Panel desiredPanel);



                var devices = await Windows.Devices.Enumeration.DeviceInformation.FindAllAsync(Windows.Devices.Enumeration.DeviceClass.VideoCapture);
                SettingsCamera.Items.Clear();
                //_deviceList = new List<Windows.Devices.Enumeration.DeviceInformation>();
                // Add the devices to deviceList
                if (devices.Count > 0)
                {
                    for (var i = 0; i < devices.Count; i++)
                    {
                       // _deviceList.Add(devices[i]);
                        SettingsCamera.Items.Add(devices[i].Name);
                    }
                }

                else
                {
                    Debug.WriteLine("No camera device is found ");
                }
        }

private async void SettingsCamera_SelectionChanged(object sender,SelectionChangedEventArgs e){
            if (SettingsCamera.SelectedIndex == 0)
            {

                try
                {
                    var allVideoDevices = await DeviceInformation.FindAllAsync(DeviceClass.VideoCapture);
                    //SettingsMicrophone.Items.Clear();
                    var frontCamera = allVideoDevices.FirstOrDefault(d => d.EnclosureLocation.Panel == Windows.Devices.Enumeration.Panel.Front);


                    if (allVideoDevices.Count == 0)
                    {
                        SettingsCamera.Items.Add(frontCamera.Name);
                    }
                }
                catch (NullReferenceException)
                {
                    //audioExist = false;
                    SettingsCamera.Items.Add("No michrophone on your system");
                }




            }
            else if (SettingsCamera.SelectedIndex == 1 && SettingsCamera.SelectedIndex == 2 && SettingsCamera.SelectedIndex == 3)
            {

                try
                {
                    var allVideoDevices = await DeviceInformation.FindAllAsync(DeviceClass.VideoCapture);
                    var backCamera = allVideoDevices.FirstOrDefault(d => d.EnclosureLocation.Panel == Windows.Devices.Enumeration.Panel.Front);
                    //SettingsMicrophone.Items.Clear();
                    if (allVideoDevices.Count >=2)
                    {
                        SettingsCamera.Items.Add(backCamera.Name);
                    }
                    SettingsCamera.Items.Add(backCamera.Name);

                    //make first cam default
                }
                catch (NullReferenceException)
                {
                    //audioExist = false;
                    SettingsCamera.Items.Add("No michrophone on your system");
                }

            }


        }

回答1:

I tested your code with MobileEmulator version 10240, the following image shows what I get:

By my side, if you select the item "SocCaptureSim RFC", the SelectedIndex is 0, and if you select the item "SocCaptureSim FFC", the SelectedIndex is 1.

But according to your code of SettingsCamera_SelectionChanged(object sender,SelectionChangedEventArgs e) method, when I select the item "SocCaptureSim FFC", nothing will happen, because your condition of the else if is SettingsCamera.SelectedIndex == 1 && SettingsCamera.SelectedIndex == 2 && SettingsCamera.SelectedIndex == 3, a ComboBox doesn't support mutil-selection.

So maybe what you want is else if (SettingsCamera.SelectedIndex == 1 || SettingsCamera.SelectedIndex == 2 || SettingsCamera.SelectedIndex == 3).

There are two other problems in your code, DeviceInformation device = FindCameraDeviceByPanelAsync(Windows.Devices.Enumeration.Panel desiredPanel); in the InitializeCameraAsync() method, although you didn't post the code of FindCameraDeviceByPanelAsync(Windows.Devices.Enumeration.Panel desiredPanel) method, according to the left code, I think you pass the wrong parameter here.

And in the InitializeCameraAsync() method, I can understand that you want to find all the camera device and add the device to the list of ComboBox, but when you select index 0,

if (allVideoDevices.Count == 0)
{
    SettingsCamera.Items.Add(frontCamera.Name);
}

This code make no sense here, if allVideoDevices.Count == 0, this var frontCamera = allVideoDevices.FirstOrDefault(d => d.EnclosureLocation.Panel == Windows.Devices.Enumeration.Panel.Front); will cause an null pointer error at first.

Since I didn't see any of your code for opening a camera to take photos or record, you can refer to the official Basic camera app sample, see how to get a camera to work.

来源：https://stackoverflow.com/questions/35526206/how-to-set-a-selected-camera-with-combobox-in-windows-10-universal-app