WP8 中 PhotoCaptureDevice 中的 InvalidOperationException答案

【问题标题】：InvalidOperationException in PhotoCaptureDevice in WP8WP8 中 PhotoCaptureDevice 中的 InvalidOperationException
【发布时间】：2014-01-09 13:09:03
【问题描述】：

当我在 windows phone 8 相机应用程序中调用 await PhotoCaptureDevice.OpenAsync(..) 时会抛出 InvalidOperationException。

System.InvalidOperationException：操作无效，因为对象的当前状态。在 System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess（任务任务）在 System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification（任务任务）在 System.Runtime.CompilerServices.TaskAwaiter`1.GetResult() 在 JPMC.Controls.CaptureTaskLauncher.d_6.MoveNext() --- 堆栈结束从先前引发异常的位置跟踪 --- 在 System.Runtime.CompilerServices.AsyncMethodBuilderCore.b_0（对象州）}

但还有一件事是，当我第一次运行相机测试时，它会完美运行，即 PhotoCaptureDevice 已正确初始化，但是当我从另一个页面返回相机测试时，它会出现上述错误。那么，谁能帮我解决这个问题？

谢谢

【问题讨论】：

标签： windows-phone-8 camera

【解决方案1】：

您是否尝试过在离开页面之前使用 PhotoCaptureDevice.Close() 和 Dispose() 释放资源？

【讨论】：

是的，我试过了，但是没用。之后也会抛出异常。
那么您将需要显示更多代码（或者我应该说 - 至少一些代码）来显示您如何初始化 PhotoCaptureDevice 等。

【解决方案2】：

 private static PhotoCaptureDevice d = null;
        public static async Task<bool> InitializeCamera(CameraSensorLocation sensorLocation)
        {
            bool catchValue = true;
            try
            {
                Windows.Foundation.Size initialResolution = new Windows.Foundation.Size(640, 480);
                Windows.Foundation.Size previewResolution = new Windows.Foundation.Size(640, 480);
                Windows.Foundation.Size captureResolution = new Windows.Foundation.Size(640, 480);
                d = await PhotoCaptureDevice.OpenAsync(sensorLocation, initialResolution);
                await d.SetPreviewResolutionAsync(previewResolution);
                await d.SetCaptureResolutionAsync(captureResolution);               
                d.SetProperty(KnownCameraGeneralProperties.PlayShutterSoundOnCapture, true);
                MemoryStream stream = new MemoryStream();                
                CameraCaptureSequence sequence = d.CreateCaptureSequence(1);
                sequence.Frames[0].CaptureStream = stream.AsOutputStream();
                await d.PrepareCaptureSequenceAsync(sequence);                
                await sequence.StartCaptureAsync();                            
                if (stream.Length > 0)
                {
                    d.Dispose();
                    d = null;
                    stream.Dispose();
                    stream = null;
                    return true;
                }
                else
                {
                    d.Dispose();
                    d = null;
                    stream.Dispose();
                    stream = null;
                }
                return false;
            }
            catch (Exception ex)
            {
                catchValue = false;
            }
            if (!catchValue)
            {
                Windows.Foundation.Size initialResolution = new Windows.Foundation.Size(640, 480);
                Windows.Foundation.Size previewResolution = new Windows.Foundation.Size(640, 480);
                Windows.Foundation.Size captureResolution = new Windows.Foundation.Size(640, 480);

                 d = await PhotoCaptureDevice.OpenAsync(sensorLocation,initialResolution);

                await d.SetPreviewResolutionAsync(previewResolution);
                await d.SetCaptureResolutionAsync(captureResolution);

                d.SetProperty(KnownCameraGeneralProperties.PlayShutterSoundOnCapture, true);
                MemoryStream stream = new MemoryStream();

                CameraCaptureSequence sequence = d.CreateCaptureSequence(1);
                sequence.Frames[0].CaptureStream = stream.AsOutputStream();
                await d.PrepareCaptureSequenceAsync(sequence);

                await sequence.StartCaptureAsync();

                if (stream.Length > 0)
                {
                    d.Dispose();
                    d = null;
                    stream.Dispose();
                    stream = null;
                    return true;
                }
                else
                {
                    d.Dispose();
                    d = null;
                    stream.Dispose();
                    stream = null;
                }
                return false;
            }
            return false;

        }

【讨论】：