学步园

创建WPF程序的三种方式:

1.只使用代码

2.使用代码和未经编译的标记(XAML)

3.使用代码和编译过的标记(BAML)

第一种不写了,比较简单

第二种:

所谓的第二种方法就是直接读一个XAML文件,解析它并创建界面元素,要注意的是要读的XAML文件属性要设置成如下的样子

        private Button button1;        

        public Window1(string xamlFile)
        {
            InitializeComponent(xamlFile);
        }                

        private void InitializeComponent(string xamlFile)
        {
            // Configure the form.
            this.Width = this.Height = 285;
            this.Left = this.Top = 100;
            this.Title = "Dynamically Loaded XAML";

            // Get the XAML content from an external file.
            DependencyObject rootElement;
            using (FileStream fs = new FileStream(xamlFile, FileMode.Open))
            {
                rootElement = (DependencyObject)XamlReader.Load(fs);
            }

            // Insert the markup into this window.
            this.Content = rootElement;                       

            // Find the control with the appropriate name.
            //button1 = (Button)LogicalTreeHelper.FindLogicalNode(rootElement, "button1");
            FrameworkElement frameworkElement = (FrameworkElement)rootElement;
            button1 = (Button)frameworkElement.FindName("button1");

            // Wire up the event handler.
            button1.Click += new RoutedEventHandler(button1_Click);
        }
        
        private void button1_Click(object sender, RoutedEventArgs e)
        {
            button1.Content = "Thank you.";
        }
    }

上面直接把Window1.xaml从硬盘读到文件流中,再转化成DependencyObject对象,DependencyObject是所有WPF控件继承的基类.

上面被注释的代码

button1 = (Button)LogicalTreeHelper.FindLogicalNode(rootElement, "button1");

与

FrameworkElement frameworkElement = (FrameworkElement)rootElement;
            button1 = (Button)frameworkElement.FindName("button1");

是等效的,LogicalTreeHelper是一个辅助类,具有查找一棵完整控件对象树的能力,这个示例中XAML文件中的根元素是DockPanel,DockPanel又继承自FrameworkElement类,所以使用FrameworkElement.FindName()方法同样可以找到控件对象.

第三种:

这种方法是VS自己支持的,所有代码都是自动生成的,不用我们人为去编码,即把XAML编译成BAML文件,再嵌入dll中作为资源保存,程序运行时再从dll中读出来. 读BMAL比直接读XMAL文件效率要高,因为BMAL已经经过了优化,文件体积也比XMAL小. 编译器在编译成会生成一个BMAL文件,和一个分部类,它们会放在项文件夹的obj\Debug子文件夹中.

下面来看看这个VS自动生成的部分类,Window1.g.cs (只呈现主要逻辑代码,省略掉非关键部分)

    /// <summary>
    /// Window1
    /// </summary>
    public partial class Window1 : System.Windows.Window, System.Windows.Markup.IComponentConnector {
        
       
        internal System.Windows.Controls.TextBox txtQuestion;
        
        internal System.Windows.Controls.Button cmdAnswer;
        
        internal System.Windows.Controls.TextBox txtAnswer;
        
        #line default
        #line hidden
        
        private bool _contentLoaded;
        
        /// <summary>
        /// InitializeComponent
        /// </summary>
        public void InitializeComponent() {
            if (_contentLoaded) {
                return;
            }
            _contentLoaded = true;
            System.Uri resourceLocater = new System.Uri("window1.baml", System.UriKind.Relative);
            
            System.Windows.Application.LoadComponent(this, resourceLocater);
            
            #line default
            #line hidden
        }
        
       ......
        void System.Windows.Markup.IComponentConnector.Connect(int connectionId, object target) {
            switch (connectionId)
            {
            case 1:
            this.txtQuestion = ((System.Windows.Controls.TextBox)(target));
            return;
            case 2:
            this.cmdAnswer = ((System.Windows.Controls.Button)(target));
            
            this.cmdAnswer.Click += new System.Windows.RoutedEventHandler(this.cmdAnswer_Click);
            

            return;
            case 3:
            this.txtAnswer = ((System.Windows.Controls.TextBox)(target));
            return;
            }
            this._contentLoaded = true;
        }
    }

方法二中的XamlReader用处很大,下面的代码摘自这个地方

通过XamlReader 动态构建并实例化一个Window

//XamlReader  
StringBuilder strXMAL = new StringBuilder("<Window ");
strXMAL.Append("xmlns=\"http://schemas.microsoft.com/winfx/2006/xaml/presentation\" ");
strXMAL.Append("xmlns:x=\"http://schemas.microsoft.com/winfx/2006/xaml\" ");
strXMAL.Append("Title=\"Window2\" Height=\"600\" Width=\"600\">");
strXMAL.Append("</Window>");
var window = (Window)XamlReader.Parse(strXMAL.ToString());
window.ShowDialog();

作者还自己实现了BMAL文件的Reader和Writer,有兴趣可以研究研究,一般情况下也用不上的