正确清理 MediaCapture 资源 [英] Cleaning up MediaCapture resources properly

问题描述

对于 Windows Phone 8.1 应用，我必须录制视频.

For a Windows Phone 8.1 app I have to record a video.

我使用了这个说明，它基本上有效......http://msdn.microsoft.com/en-us/library/windows/apps/xaml/hh868171.aspx

I used this instructions and it works basically... http://msdn.microsoft.com/en-us/library/windows/apps/xaml/hh868171.aspx

...但我没有得到 App.xaml.cs 中的清理部分

... but I do not get the cleaning up part within the App.xaml.cs

public MediaCapture MediaCapture { get; set; }
public CaptureElement PreviewElement { get; set; }
public bool IsRecording { get; set; }
public bool IsPreviewing { get; set; }

public async Task CleanupCaptureResources()
{
    if (IsRecording && MediaCapture != null)
    {
        await MediaCapture.StopRecordAsync();
        IsRecording = false;
    }
    if (IsPreviewing && MediaCapture != null)
    {
        await MediaCapture.StopPreviewAsync();
        IsPreviewing = false;
    }

    if (MediaCapture != null)
    {
        if (PreviewElement != null)
        {
            PreviewElement.Source = null;
        }
        MediaCapture.Dispose();
    }
}

private async void OnSuspending(object sender, SuspendingEventArgs e)
{
    var deferral = e.SuspendingOperation.GetDeferral();

    //cleanup camera resources
    await CleanupCaptureResources();

    deferral.Complete();
}

我不明白 App.xaml.cs 和 VideoRec.xaml(预览元素所在的地方)之间的连接是如何工作的.这可能是一件非常基本的事情......我非常感谢初学者如何处理 MediaCapture 的每个提示或教程链接.我发现的一切都是为了高级.

I don't get how the connection between App.xaml.cs and VideoRec.xaml (whrere the preview element is) has to work. This is probably a very basic thing... I am very grateful for every hint or a link for a tutorial for beginners how to handle MediaCapture at all. Everything I have found is for advanced.

推荐答案

我想说的是，适当的清洁 MediaCapture 是拍摄照片/视频最重要的部分，也是 MSDN 说:

I would say that proper cleaning MediaCapture is the most important part of takieng a photo/video also MSDN says:

注意在 Windows Phone 上，音乐和媒体应用程序应清理 Suspending 事件处理程序中的 MediaCapture 对象和相关资源，并在 Resuming 事件处理程序中重新创建它们.

Note On Windows Phone, music and media apps should clean up the MediaCapture object and associated resources in the Suspending event handler and recreate them in the Resuming event handler.

如果不清理 MediaCapture 元素会发生什么?- 就我而言，当我尝试使用 MediaCapture(例如默认照片应用程序)运行其他应用程序时，我的手机挂了.

What happens when you don't clean your MediaCapture element? - in my case, when I've tried, my phone hung when I've run other application using MediaCapture (for example default photo app).

回到你的问题 - App.xaml.cs 和 VideoREc.xaml 之间的连接 - 看看所有变量(在这种情况下是属性)MediaCapture、PreviewElement、IsRecording 和 IsPreviewing 在 App 类中定义 - 它们是为整个应用程序定义的.我怀疑 VideoRec.xaml 仅使用了 App.xaml.cs 中定义的那些属性的引用.

Going back to your question - connection between App.xaml.cs and VideoREc.xaml - look that all variables (properties in this case) MediaCapture, PreviewElement, IsRecording and IsPreviewing are defined in class App - they are defined for the whole app. I suspect that VideoRec.xaml uses only a reference of those properties defined in App.xaml.cs.

您还应该知道 Suspending/Resuming 事件是为整个应用程序定义的，并且在发生此类事件时都会触发它们.它什么时候发生?- 在你离开你的应用程序之后(只注意调试模式 - 连接到计算机时它的工作方式几乎没有什么不同).详细了解 MSDN 上的生命周期事件.这些事件是清理/恢复 MediaCapture 资源的最佳事件.

You should also be aware that Suspending/Resuming events are defined for the whole app and they are all fired when such an event occurs. When does it occur? - just after you navigate away from your app (only look out for Debug mode - it works little different when connected to computer). More about lifecycle events at MSDN. Those events are the best one to clean/restore MediaCapture resources.

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