How to create a dialog like CameraCaptureUI.Captur

问题:

I would like to create a library behaving like the CaptureFileAsync method, i.e. on a method call it would open up a full screen page with standard back navigation and return result to the caller.

I want to be able to call it the same way CaptureFileAsync is called:

var dialog = new Library.Dialog();
var result = await dialog.Show();

In the Show method I'm currently navigating to my own page and returning a Task which can be awaited by the caller:

public Task<string> Show()
{
    var task = new Task<string>(() => result);

    var frame = ((Window.Current.Content) as Frame);
    frame.Navigate(typeof(DialogPage));

    return task;
}

I call task.Start() when the dialog is being closed (either cancelled by navigating back or confirmed by pressing a button) which causes the result to be returned to the awaiting caller.

The problem is that when Frame.GoBack() is called, a new instance of the previous page is created and the result gets returned to the old instance which is not displayed any more. This is not how CaptureFileAsync works: in its case the same instance of the calling page is kept.

My question is: how can I display a page from my library without affecting the frame navigation and inadvertently causing a new instance of the calling page to be created?

回答1:

You can put all your UI on a Popup.

回答2:

Take a look at PopupHelper.

It abstracts all the ickines of using Popups and takes care of animation, disabling access to controls etc.

回答3:

I had the same issue, and this is what I came up with:

XAML

<Grid x:Name="MainGrid" 
      Background="#7F000000">
    <Grid Width="480" Height="180" HorizontalAlignment="Center" VerticalAlignment="Center" Background="Black">
        <StackPanel>
            <TextBlock Text="Custom Capture!" Style="{StaticResource HeaderTextBlockStyle}" Margin="20"/>
            <StackPanel Orientation="Horizontal" HorizontalAlignment="Center">
                <Button x:Name="SaveButton" Content="Save" HorizontalAlignment="Center" Click="CloseButton_Click"/>
                <Button x:Name="CloseButton" Content="Close" HorizontalAlignment="Center" Click="CloseButton_Click"/>
            </StackPanel>
        </StackPanel>
    </Grid>
</Grid>

The Control

public sealed partial class CustomCaptureControl : UserControl
{
    private StorageFile file;
    private ManualResetEvent reset;
    private Popup _mainPopup;

    /// <summary>
    /// 
    /// </summary>
    public CustomCaptureControl()
    {
        this.InitializeComponent();

        Rect windowBounds = CoreWindow.GetForCurrentThread().Bounds;
        this.MainGrid.Width = windowBounds.Width;
        this.MainGrid.Height = windowBounds.Height;
    }

    /// <summary>
    /// 
    /// </summary>
    /// <returns></returns>
    public async Task<StorageFile> ShowAsync()
    {
        StorageFile file = await Task.Run(() => this.GetFile());
        return file;
    }

    /// <summary>
    /// 
    /// </summary>
    /// <returns></returns>
    private async Task<StorageFile> GetFile()
    {
        //Launch Popup in UI thread
        await CoreApplication.MainView.CoreWindow.Dispatcher.RunAsync(CoreDispatcherPriority.Normal, () => 
        {
            this._mainPopup = new Popup();
            this._mainPopup.Child = this;
            this._mainPopup.IsOpen = true;
        });

        //Await user input
        await Task.Run(() => this.AwaitUserInput());

        return this.file;
    }

    /// <summary>
    /// 
    /// </summary>
    /// <returns></returns>
    private Task AwaitUserInput()
    {
        return Task.Run(() =>
        {
            this.reset = new ManualResetEvent(false);
            WaitHandle.WaitAll(new WaitHandle[] { this.reset });
        });
    }

    /// <summary>
    /// 
    /// </summary>
    /// <param name="sender"></param>
    /// <param name="e"></param>
    private async void CloseButton_Click(object sender, RoutedEventArgs e)
    {
        Uri fileURI = new Uri("ms-appx:///Assets/SomeFile.pdf");
        this.file = await StorageFile.GetFileFromApplicationUriAsync(fileURI);

        this.reset.Set();

        this._mainPopup.IsOpen = false;
        this._mainPopup = null;
    }
}

Usage

CustomCaptureControl capture = new CustomCaptureControl();
StorageFile file = await capture.ShowAsync();