對象序列化（六）：應用執行個體->WPF對象的XAML序列化

WPF使用XAML來描述使用者介面，每個XAML元素往往對應著相應的WPF對象，元素的屬性對應著對象的屬性。

由於XAML元素與WPF對象之前存在著這種對應關係，其實可以將XAML代碼看成是WPF對象“序列化”後的結果。

WPF提供了XamlWriter 和 XamlReader  兩個類實現WPF對象的XAML序列化和還原序列化。

 

樣本項目：

展示了一個繪圖板，使用者用滑鼠點擊此繪圖板，程式將以隨機顏色和大小繪製一個矩形，點擊“儲存”按鈕，當前圖形將被儲存到磁碟上一個名為“PicData.dat” 的檔案中，點擊“重建”按鈕，將恢複上次儲存的圖形。

 

前台的XAML代碼：

<Window x:Class="SaveAndReloadXAMLObject.Window1"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="WPF對象的序列化" Height="300" Width="320">
<DockPanel>
<StackPanel DockPanel.Dock="Top" Orientation="Horizontal" HorizontalAlignment="Center" Margin="10">
<Button Margin="5" Width="80" Name="btnSave" Click="btnSave_Click">儲存</Button>
<Button Margin="5" Width="80" Name="btnClear" Click="btnClear_Click">清空</Button>    
<Button Margin="5" Width="80" Name="btnLoad" Click="btnLoad_Click">重建</Button>
</StackPanel>
<Border x:Name="DrawPanelBorder" BorderBrush="Black"  Background="Black" CornerRadius="5" Margin="5" Padding="2">
<Canvas x:Name="DrawPanel"  Background="White" MouseDown="Canvas_MouseDown"></Canvas>
</Border>
</DockPanel>
</Window>

 

後台CS代碼：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using System.Windows.Markup;
using System.IO;

namespace SaveAndReloadXAMLObject
{
/// <summary>
/// Window1.xaml 的互動邏輯
/// </summary>
    public partial class Window1 : Window
    {
public Window1()
        {
            InitializeComponent();
            CurCanvas = DrawPanel;
        }

private Canvas CurCanvas = null;
private void Canvas_MouseDown(object sender, MouseButtonEventArgs e)
        {
//擷取當前滑鼠的位置
            Point curP = e.GetPosition(sender as Canvas);
            Random ran = new Random();
            Color clr = Color.FromRgb((byte)ran.Next(0, 255), (byte)ran.Next(0, 255), (byte)ran.Next(0, 255));
            Brush br = new SolidColorBrush(clr);
            Rectangle rect = new Rectangle();
            rect.Width = ran.Next(1, (int)(CurCanvas.ActualWidth - curP.X - 5));
            rect.Height = ran.Next(1, (int)(CurCanvas.ActualHeight - curP.Y - 5));
            rect.SetValue(Canvas.TopProperty, curP.Y);
            rect.SetValue(Canvas.LeftProperty, curP.X);
            rect.Fill = br;
            CurCanvas.Children.Add(rect);



        }

private void btnSave_Click(object sender, RoutedEventArgs e)
        {
using (FileStream fs = new FileStream("PicData.dat", FileMode.Create))
            {
//當需要儲存當前圖形時，調用XamlWriter的以下方法將Canvas對象直接序列化到檔案流中
                XamlWriter.Save(CurCanvas, fs);

                MessageBox.Show("資料已儲存");
            }
        }
private void btnLoad_Click(object sender, RoutedEventArgs e)
        {
using (FileStream fs = new FileStream("PicData.dat", FileMode.Open))
            {
//double oldWidth = DrawPanelBorder.ActualWidth;
//double oldHeight = DrawPanelBorder.ActualHeight;
//調用XamlReader的方法從檔案流中重建canvas對象
                CurCanvas = XamlReader.Load(fs) as Canvas;
//CurCanvas.Width = oldWidth;
//CurCanvas.Height = oldHeight;
                CurCanvas.MouseDown += Canvas_MouseDown;
                DrawPanelBorder.Child = CurCanvas;

            }
        }

private void btnClear_Click(object sender, RoutedEventArgs e)
        {
            CurCanvas.Children.Clear();
        }

    }
}

 

如果用記事本開啟 PicData.dat檔案。可以看到其內容為XAML代碼。它就是XamlWriter 的序列化結果。

<Canvas Background="#FFFFFFFF" Name="DrawPanel" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"><Rectangle Fill="#FF0A83CB" Width="139" Height="103" Canvas.Left="58" Canvas.Top="24.1633333333333" /></Canvas>