Reflection failure when attempting to access Micro

问题:

I am developing one Flash Light application in Silverlight for windows phone 8. Currently I am deeply stuck in one issue for the use of "Microsoft.Phone.Media.Extended" assembly. Flash Light Application for Windows phone 7 is already live in Windows Phone Marketplace and it is working very fine for Windows Phone 7 but it is not working for Windows Phone 8 because of "Microsoft.Phone.Media.Extended" dll.

After converting WP7 app into wp8 and run then I got this type of error message:

Could not load file or assembly 'Microsoft.Phone.Media.Extended,Version=7.0.0.0, Culture=neutral, PublicKeyToken=24eec0d8c86cda1e' or one of its dependencies. The system can not find file specific."

According to following link for Windows Phone-specific features: http://msdn.microsoft.com/en-us/library/windowsphone/develop/jj206947(v=vs.105).aspx

If you were using reflection to access the API in this assembly, because they were not publicly exposed, your app may fail on a Windows Phone 8 device. Remove the calls to this assembly and use the publicly exposed media API.

I an not understanding how to use publicly exposed media API. I used Microsoft.Phone.Media.Extended using reflaction in Windows Phone 7. Is there any direct method for accessing Microsoft.Phone.Media.Extended in Windows Phone 8 or other way to solve this?

Thanks.

========================================================================== Edited Question:

Hi,

As per the thread, we used "VideoTorchMode" enumeration to make flashlight ON. As per that, I used AudioVideoCaptureDevice class using Windows.Phone.Media.Capture namespace with following code:

    var objDevice = await AudioVideoCaptureDevice.OpenAsync(CameraSensorLocation.Back, AudioVideoCaptureDevice.GetAvailableCaptureResolution(CameraSensorLocation.Back).First());
    objDevice .SetProperty(KnownCameraAudioVideoProperties.VideoTorchMode, VideoTorchMode.On);

I want to keep the flash light on but without capturing video. So, i have not initialized video capture code. The issue is, i don’t have WP8 yet and in simulator i am not able to test this.

Can any one confirm that once i put this code, my app will work as Flashlight-X where light will be on without blinking and also it will not get crashed in WP8.

Thanks

回答1:

Microsoft.Phone.Media.Extended is a private API in WP7 that wasn't meant to be used by 3rd party developers. That API doesn't exist or works on WP8.

For WP8 flashlight use the AudioVideoCaptureDevice known property of VideoTorchMode=On. Also, make sure to handle failures like exceptions or devices that don't have a Camera Torch by showing a white screen.

Here's a code sample that turns on the camera flash on my Lumia 820 and Lumia 920:

var sensorLocation = CameraSensorLocation.Back;

try
{
    // get the AudioViceoCaptureDevice
    var avDevice = await AudioVideoCaptureDevice.OpenAsync(sensorLocation,
        AudioVideoCaptureDevice.GetAvailableCaptureResolutions(sensorLocation).First());

    // turn flashlight on
    var supportedCameraModes = AudioVideoCaptureDevice
        .GetSupportedPropertyValues(sensorLocation, KnownCameraAudioVideoProperties.VideoTorchMode);
    if (supportedCameraModes.ToList().Contains((UInt32)VideoTorchMode.On))
    {
        avDevice.SetProperty(KnownCameraAudioVideoProperties.VideoTorchMode, VideoTorchMode.On);

        // set flash power to maxinum
        avDevice.SetProperty(KnownCameraAudioVideoProperties.VideoTorchPower,
            AudioVideoCaptureDevice.GetSupportedPropertyRange(sensorLocation, KnownCameraAudioVideoProperties.VideoTorchPower).Max);
    }
    else
    {
        ShowWhiteScreenInsteadOfCameraTorch();
    }

}
catch(Exception ex)
{
    // Flashlight isn't supported on this device, instead show a White Screen as the flash light
    ShowWhiteScreenInsteadOfCameraTorch();
}

Make sure to add the required capabilities and requirements to your WP8 app when using the camera torch (ISV_Camera, Microphone, and ID_REQ_BACK_Camera).

回答2:

What about getting this assembly from somewhere and adding it to your XAP directly (try asking on XDA developers)? This might work, if it's signed and not requiring any special capabilities.

回答3:

If you use the new API to "record" a video, then using the VideoTorchMode enumeration might do just want you want to create a "flashlight" effect.