FIleSavePicker保存0字节文件Windows 8

Question

因此，我现在被告知，FileSavePicker只创建一个空白文件，我必须编写额外的代码才能真正写入该文件。我已经在WriteToFile之后启动了一个任务FileSavePicker，但我不知道如何完成它。使用FileSavePicker，用户选择希望将文件保存到的文件夹。在WriteToFile代码中，我要指出哪些地方，以及如何将文件源准确地放入其中？要保存的文件都与应用程序一起打包。我在这里以x.mp3为例。

    public class SoundData : ViewModelBase
    {
        public string Title { get; set; }
        public string FilePath { get; set; }



        public RelayCommand<string> SaveSoundAs { get; set; }

        private async void ExecuteSaveSoundAs(string soundPath)
        {

        string path = @"appdata:/x.mp3";
        StorageFolder folder = Windows.ApplicationModel.Package.Current.InstalledLocation;
        StorageFile file = await folder.GetFileAsync(path);



                {
                    FileSavePicker savePicker = new FileSavePicker();
                    savePicker.SuggestedSaveFile = file;
                    savePicker.FileTypeChoices.Add("MP3", new List<string>() { ".mp3" });
                    savePicker.ContinuationData.Add("SourceSound", soundPath);
                    savePicker.SuggestedFileName = this.Title;
                    savePicker.PickSaveFileAndContinue();

                }

        }

        public async void ContinueFileSavePicker(FileSavePickerContinuationEventArgs args)
        {
            string soundPath = (string)args.ContinuationData["SourceSound"];
            StorageFile file = args.File;
            if (file != null)
            {
                // Prevent updates to the remote version of the file until we finish making changes and call CompleteUpdatesAsync.
                CachedFileManager.DeferUpdates(file);
                // write to file



                await FileIO.WriteTextAsync(file, file.Name);
                // Let Windows know that we're finished changing the file so the other app can update the remote version of the file.
                // Completing updates may require Windows to ask for user input.
                FileUpdateStatus status = await CachedFileManager.CompleteUpdatesAsync(file);
                if (status == FileUpdateStatus.Complete) ;

            }
        }



        public SoundData()
        {
            SaveSoundAs = new RelayCommand<string>(ExecuteSaveSoundAs);
        }







    }
}

Answer 1

对于Windows，您应该遵循这个如何文档化。与Silverlight应用程序相比，工作流已经发生了很大变化。你的应用程序不再像以前那样恢复旧任务了。

您不需要遵循文档中的所有步骤，但是一个重要的部分是在App.xaml.cs中遍历App.xaml.cs方法。在其中，您将调用您的ContinueFileSavePicker方法。

下面是您也可以下载的一个例子，这应该会有所帮助。

更新

如果要保存将随应用程序传送的文件，请尝试以下代码来初始化选择器

// Get the local file that is shipped with the app
// file but be "content" and not "resource"
string path = @"Assets\Audio\Sound.mp3";
StorageFolder folder = Windows.ApplicationModel.Package.Current.InstalledLocation;
StorageFile file = await folder.GetFileAsync(path);

// Show the picker
FileSavePicker savePicker = new FileSavePicker();
// Set the file that will be saved
savePicker.SuggestedSaveFile = file;
savePicker.SuggestedFileName = "Sound";
savePicker.FileTypeChoices.Add("MP3", new List<string>() { ".mp3" });
savePicker.PickSaveFileAndContinue();

您还需要确保侦听PhoneApplicationService的PhoneApplicationService事件。当应用程序从选择器返回时，这个事件就会被触发(在8.1 Silverlight应用程序中)。这就是您想要调用ContinueFileSavePicker方法的地方。如果你愿意的话，你可以把逻辑放进去。

订阅xaml中的事件：

<Application.ApplicationLifetimeObjects>
    <!--Required object that handles lifetime events for the application-->
    <shell:PhoneApplicationService
        ContractActivated="Application_ContractActivated"
        Launching="Application_Launching" Closing="Application_Closing"
        Activated="Application_Activated" Deactivated="Application_Deactivated"/>
</Application.ApplicationLifetimeObjects>

在App.xaml.cs中：

private async void Application_ContractActivated(object sender, Windows.ApplicationModel.Activation.IActivatedEventArgs e)
{
    var args = e as FileSavePickerContinuationEventArgs ;
    if (args != null)
    {
        StorageFile file = args.File; 
        if (file != null) 
        { 
            // Prevent updates to the remote version of the file until we finish making changes and call CompleteUpdatesAsync. 
            CachedFileManager.DeferUpdates(file); 
            // write to file 
            await FileIO.WriteTextAsync(file, file.Name); 
            // Let Windows know that we're finished changing the file so the other app can update the remote version of the file. 
            // Completing updates may require Windows to ask for user input. 
            FileUpdateStatus status = await CachedFileManager.CompleteUpdatesAsync(file); 
        }
    }
}