实用的MVVM：ImageView

最近在学习WPF，遇到一本入门好书，推荐给大家《Windows Presentation Foundation 4.5 Cookbook》

做项目首先要从MVVM开始，现在把他的Simple MVVM例子介绍给大家，感觉简单但很实用

1. App.xaml.cs中重载OnStartup

protected override void OnStartup(StartupEventArgs e) {

    base.OnStartup(e);

    var mainWindow = new MainWindow();

    mainWindow.DataContext = new ImageData();

    mainWindow.Show();

}

2. ViewModel的实现

 public  class ImageData:INotifyPropertyChanged

  {

      public ImageData()

      {

          _openImageFileCommand = new OpenImageFileCommand(this);

          _zoomCommand = new ZoomCommand(this);



      }

      public ICommand OpenImageFileCommand { get { return _openImageFileCommand; } }

      public ICommand ZoomCommand { get { return _zoomCommand; } }

      public string ImagePath

        {

            get { return _imagePath; }

            set

            {

                _imagePath = value;

                this.RaisePropertyChanged("ImagePath");

            }

        }

      public double Zoom

      {

          get { return _zoom; }

          set

          {

              _zoom = value;

              this.RaisePropertyChanged("Zoom");

          }

      }

      private void RaisePropertyChanged(string propertyName)

        {

            var handler = PropertyChanged;

            if (handler == null)

                return;

            handler(this, new PropertyChangedEventArgs(propertyName));

        }

      public event PropertyChangedEventHandler PropertyChanged;

      private double _zoom = 1.0;

      private string _imagePath;

      private OpenImageFileCommand _openImageFileCommand;

      private ZoomCommand _zoomCommand;

  }

View Code

3. 下面看看View是怎么做的，除了Xaml加绑定，不再需要其它多余的代码了。

<Window xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 

    xmlns:local="clr-namespace:CH07.RoutedCommands" 

    xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 

    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" mc:Ignorable="d" 

    x:Class="CH07.RoutedCommands.MainWindow"

    d:DataContext="{d:DesignInstance Type=local:ImageData, IsDesignTimeCreatable=True}"

    Title="Image Viewer" Height="350" Width="525">

    <Grid>

        <Grid.RowDefinitions>

            <RowDefinition Height="Auto" />

            <RowDefinition />

        </Grid.RowDefinitions>

        <ToolBar FontSize="14">

            <Button Content="Open..." Command="{Binding OpenImageFileCommand}" Margin="6"/>

            <Button Content="Zoom In" Command="{Binding ZoomCommand}" CommandParameter="ZoomIn" Margin="6"/>

            <Button Content="Zoom Out" Command="{Binding ZoomCommand}" CommandParameter="ZoomOut" Margin="6"/>

            <Button Content="Normal" Command="{Binding ZoomCommand}" CommandParameter="ZoomNormal" Margin="6"/>

        </ToolBar>

        <ScrollViewer Grid.Row="1" HorizontalScrollBarVisibility="Auto" VerticalScrollBarVisibility="Auto">

            <Image Source="{Binding ImagePath}" Stretch="None">

                <Image.LayoutTransform>

                    <ScaleTransform ScaleX="{Binding Zoom}" ScaleY="{Binding Zoom}" />

                </Image.LayoutTransform>

            </Image>

        </ScrollViewer>

    </Grid>

</Window>

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4. 还有ViewModel里的Command
ZoomCommand里的代码

   public class ZoomCommand:ICommand

    {

        public ZoomCommand(ImageData data)

        {

            _data = data;

        }

        public bool CanExecute(object parameter)

        {

            if (_data.ImagePath == null)

                return false;

            return _data.ImagePath.IsPicture();

        }



        public event EventHandler CanExecuteChanged

        {

            add { CommandManager.RequerySuggested += value; }

            remove { CommandManager.RequerySuggested -= value; }

        }

        private ImageData _data;



        public void Execute(object parameter)

        {

            var zoomType = (ZoomType)Enum.Parse(typeof(ZoomType), (string)parameter, true);

            switch (zoomType)

            {

                case ZoomType.ZoomIn:

                    _data.Zoom *= 1.2;

                    break;

                case ZoomType.ZoomOut:

                    _data.Zoom /= 1.2;

                    break;

                case ZoomType.ZoomNormal:

                    _data.Zoom = 1.0;

                    break;

                default:

                    break;

            }

        }

    }

    enum ZoomType

    {

        ZoomIn,

        ZoomOut,

        ZoomNormal

    }

View Code

下面是OpenImageFileCommand

  public class OpenImageFileCommand:ICommand

    {

        public OpenImageFileCommand(ImageData data)

        {

            _data = data;

        }

        public bool CanExecute(object parameter)

        {

            return true;

        }



        public event EventHandler CanExecuteChanged;



        private ImageData _data;



        public void Execute(object parameter)

        {

            var dlg = new OpenFileDialog

            {

                Filter = "图形 文件|*.jpg;*.png;*.bmp;*.gif"

            };



            if (dlg.ShowDialog()==true)

            {

                _data.ImagePath = dlg.FileName;

            }

        }

    }

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5. 其它
判断打开的文件类型

       public static bool IsPicture(this string filePath)

        {

            try

            {

                FileStream fs = new FileStream(filePath, FileMode.Open, FileAccess.Read);

                BinaryReader reader = new BinaryReader(fs);

                string fileClass;

                byte buffer;

                byte[] b = new byte[2];

                buffer = reader.ReadByte();

                b[0] = buffer;

                fileClass = buffer.ToString();

                buffer = reader.ReadByte();

                b[1] = buffer;

                fileClass += buffer.ToString();





                reader.Close();

                fs.Close();

                ////255216是jpg;7173是gif;6677是BMP,13780是PNG;7790是exe,8297是rar 

                return ((fileClass == "255216" || fileClass == "7173" || fileClass == "6677" || fileClass == "13780") ? true : false);

               

            }

            catch

            {

                return false;

            }

        }

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