如何在mvvm Windows Phone应用中拍摄当前屏幕截图

Question

How do we take screenshot in mvvm windows phone application.

I tried the below code but it doesn't work in mvvm app as it requires uielement .Any suggests how to do this in mvvm app ?

        var screenshot = new WriteableBitmap(this, null);
        var screenshotname = String.Format("Screenshooter_{0}", DateTime.Now.Ticks);
        using (var ms = new MemoryStream())
        {
            screenshot.SaveJpeg(ms, 480, 800, 0, 85);
            ms.Seek(0, SeekOrigin.Begin);

            var library = new MediaLibrary();
            var pic = library.SavePicture(screenshotname, ms);
        }

        UtilityLib.ShowMessageDialog(string.Concat("Screenshot saved as ", screenshotname));

Answer 1

Try this:

We should register each service in ViewModelLocator, as following:

using Cimbalino.Phone.Toolkit.Services; 
    using GalaSoft.MvvmLight; 
    using GalaSoft.MvvmLight.Ioc; 
    using Microsoft.Practices.ServiceLocation; 

    /// <summary> 
    /// This class contains static references to all the view models in the 
    /// application and provides an entry point for the bindings. 
    /// </summary> 
    public class ViewModelLocator 
    { 
        /// <summary> 
        /// Initializes a new instance of the ViewModelLocator class. 
        /// </summary> 
        public ViewModelLocator() 
        { 
            ServiceLocator.SetLocatorProvider(() => SimpleIoc.Default); 
            if (!SimpleIoc.Default.IsRegistered<IScreenshotService>()) 
            { 
                SimpleIoc.Default.Register<IScreenshotService, ScreenshotService>(); 
            } 
            SimpleIoc.Default.Register<MainViewModel>(); 
        } 

        /// <summary> 
        /// Gets the main view model. 
        /// </summary> 
        /// <value> 
        /// The main view model. 
        /// </value> 
        public MainViewModel MainViewModel 
        { 
            get 
            { 
                return ServiceLocator.Current.GetInstance<MainViewModel>(); 
            } 
        } 

        public static void Cleanup() 
        { 
            // TODO Clear the ViewModels 
            var viewModelLocator = (ViewModelLocator)App.Current.Resources["Locator"]; 
            viewModelLocator.MainViewModel.Cleanup(); 
        } 
    }

Then we should implement the MainViewModel as following:

using System.Windows; 
    using System.Windows.Input; 
    using System.Windows.Threading; 

    using Cimbalino.Phone.Toolkit.Services; 

    using GalaSoft.MvvmLight.Command; 
    using GalaSoft.MvvmLight; 
    /// <summary> 
    /// This class contains properties that the main View can data bind to. 
    /// </summary> 
    public class MainViewModel : ViewModelBase 
    { 
        /// <summary> 
        /// The screenshot service 
        /// </summary> 
        private readonly IScreenshotService _screenshotService; 

        /// <summary> 
        /// Initializes a new instance of the MainViewModel class. 
        /// </summary> 
        public MainViewModel(IScreenshotService screenshotService) 
        { 
            _screenshotService = screenshotService; 
            TakeScreenshotCommand = new RelayCommand(TakeScreenshot); 
        } 

        /// <summary> 
        /// Gets the take screenshot command. 
        /// </summary> 
        /// <value> 
        /// The take screenshot command. 
        /// </value> 
        public ICommand TakeScreenshotCommand { get; private set; } 

        /// <summary> 
        /// Calls to. 
        /// </summary> 
        private void TakeScreenshot() 
        { 
            _screenshotService.TakeScreenshot("CimbalinoScreenshot"); 
        } 
    }

for connect view model with the page we should add the ViewModelLocator instance in App.xaml:

XAML

<vm:ViewModelLocator x:Key="Locator" d:IsDataSource="True" />

and add the binding in main page like:

XAML

 DataContext="{Binding MainViewModel, 

Source={StaticResource Locator}}"

The MainPage.xaml can be the following:

XAML

<phone:PhoneApplicationPage x:Class="CimbalinoSample.MainPage" 
                            xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
                            xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
                            xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
                            xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
                            xmlns:phone="clr-namespace:Microsoft.Phone.Controls;assembly=Microsoft.Phone" 
                            xmlns:shell="clr-namespace:Microsoft.Phone.Shell;assembly=Microsoft.Phone" 
                            DataContext="{Binding MainViewModel, 
                                                  Source={StaticResource Locator}}" 
                            FontFamily="{StaticResource PhoneFontFamilyNormal}" 
                            FontSize="{StaticResource PhoneFontSizeNormal}" 
                            Foreground="{StaticResource PhoneForegroundBrush}" 
                            Orientation="Portrait" 
                            SupportedOrientations="Portrait" 
                            shell:SystemTray.IsVisible="True" 
                            mc:Ignorable="d"> 

    <!--  LayoutRoot is the root grid where all page content is placed  --> 
    <Grid x:Name="LayoutRoot" Background="Transparent"> 
        <Grid.RowDefinitions> 
            <RowDefinition Height="Auto" /> 
            <RowDefinition Height="*" /> 
        </Grid.RowDefinitions> 

        <!--  TitlePanel contains the name of the application and page title  --> 
        <StackPanel x:Name="TitlePanel" 
                    Grid.Row="0" 
                    Margin="12,17,0,28"> 
            <TextBlock Margin="12,0" 
                       Style="{StaticResource PhoneTextTitle2Style}" 
                       Text="Cimbalino Sample" /> 
            <TextBlock Margin="9,-7,0,0" 
                       Style="{StaticResource PhoneTextTitle2Style}" 
                       Text="ScreenshotService" /> 
        </StackPanel> 

        <!--  ContentPanel - place additional content here  --> 
        <Grid x:Name="ContentPanel" 
              Grid.Row="1" 
              Margin="12,0,12,0"> 
            <TextBlock TextWrapping="Wrap">This samples has the goal to show how to use Cimbalino Windows Phone Toolkit Media Library - ScreenshotService</TextBlock> 

            <Button Margin="0,219,0,293" 
                    Command="{Binding TakeScreenshotCommand}" 
                    Content="Take Screenshot" /> 
        </Grid> 
    </Grid> 
</phone:PhoneApplicationPage>

Source : http://code.msdn.microsoft.com/wpapps/How-to-use-Cimbalino-749562db