c# WPF中自定义加载时实现带动画效果的Form和FormItem-C#/.NET问题

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背景

　　今天我们来谈一下我们自定义的一组WPF控件Form和FormItem,然后看一下如何自定义一组完整地组合WPF控件，在我们很多界面显示的时候我们需要同时显示文本、图片并且我们需要将这些按照特定的顺序整齐的排列在一起，这样的操作当然通过定义Grid和StackPanel然后组合在一起当然也是可以的，我们的这一组控件就是将这个过程组合到一个Form和FormItem中间去，从而达到这样的效果，我们首先来看看这组控件实现的效果。

一动画效果

　　看了这个效果之后我们来看看怎么来使用Form和FormItem控件，后面再进一步分析这两个控件的一些细节信息。


<xui:TabControl Canvas.Left="356" Canvas.Top="220">
                   <xui:TabItem Header="Overview">
                       <xui:Form Margin="2" >
                           <xui:FormItem Content="Test1" Height="30"></xui:FormItem>
                           <xui:FormItem Content="Test2" Height="30"></xui:FormItem>
                           <xui:FormItem Content="Test3" Height="30"></xui:FormItem>
                       </xui:Form>
                   </xui:TabItem>
                   <xui:TabItem Header="Plumbing">
                       <xui:Form Margin="2" Columns="2" Rows="2">
                           <xui:FormItem Content="Demo1" Height="30" Margin="5 2"></xui:FormItem>
                           <xui:FormItem Content="Demo2" Height="30" Margin="5 2"></xui:FormItem>
                           <xui:FormItem Content="Demo3" Height="30" Margin="5 2"></xui:FormItem>
                           <xui:FormItem Content="Demo4" Height="30" Margin="5 2"></xui:FormItem>
                       </xui:Form>
                   </xui:TabItem>
                   <xui:TabItem Header="Clean">
                       <xui:TextBox Text="Test2" Width="220" Height=" 30" Margin="5"></xui:TextBox>
                   </xui:TabItem>
               </xui:TabControl>

　　这个里面xui命名控件是我们的自定义控件库的命名空间，这个里面的TableControl也是一种特殊的自定义的TableControl，关于这个TableControl我们后面也会进一步分析。

二自定义控件实现

　　按照上面的顺序我们先来分析Form控件，然后再分析FormItem控件的实现细节

　　2.1 Form

　　通过上面的代码我们发现Form是可以承载FormItem的，所以它是一个可以承载子控件的容器控件，这里Form是集成ItemsControl的，我们来看看具体的代码


public class Form : ItemsControl
    {
        static Form()
        {
            DefaultStyleKeyProperty.OverrideMetadata(typeof(Form), new FrameworkPropertyMetadata(typeof(Form)));
        }
 
        public double HeaderWidth
        {
            get { return (double)GetValue(HeaderWidthProperty); }
            set { SetValue(HeaderWidthProperty, value); }
        }
 
        // Using a DependencyProperty as the backing store for HeaderWidth.  This enables animation, styling, binding, etc...
        public static readonly DependencyProperty HeaderWidthProperty =
            DependencyProperty.Register("HeaderWidth", typeof(double), typeof(Form), new PropertyMetadata(70D));
 
        public int Rows
        {
            get { return (int)GetValue(RowsProperty); }
            set { SetValue(RowsProperty, value); }
        }
 
        // Using a DependencyProperty as the backing store for Rows.  This enables animation, styling, binding, etc...
        public static readonly DependencyProperty RowsProperty =
            DependencyProperty.Register("Rows", typeof(int), typeof(Form), new PropertyMetadata(0));
 
        public int Columns
        {
            get { return (int)GetValue(ColumnsProperty); }
            set { SetValue(ColumnsProperty, value); }
        }
 
        // Using a DependencyProperty as the backing store for Columns.  This enables animation, styling, binding, etc...
        public static readonly DependencyProperty ColumnsProperty =
            DependencyProperty.Register("Columns", typeof(int), typeof(Form), new PropertyMetadata(1));
 
    }

　　然后我们再来看看Form的样式文件


<Style TargetType="local:Form">
        <Setter Property="Padding" Value="10"></Setter>
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="local:Form">
                    <ScrollViewer Background="#eee" HorizontalScrollBarVisibility="Disabled" VerticalScrollBarVisibility="Auto">
                        <UniformGrid Columns="{TemplateBinding Columns}" Rows="{TemplateBinding Rows}" IsItemsHost="True" Background="Transparent" VerticalAlignment="Top" Margin="{TemplateBinding Padding}"></UniformGrid>
                    </ScrollViewer>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
        <Setter Property="ItemTemplate">
            <Setter.Value>
                <DataTemplate>
                    <ContentPresenter Content="{Binding}" Focusable="False"></ContentPresenter>
                </DataTemplate>
            </Setter.Value>
        </Setter>
    </Style>

　　这里我们使用UniformGrid作为内容承载容器，所以我们现在清楚了为什么需要定义Columns和Rows这两个依赖项属性了，这个UniformGrid是嵌套在ScrollerViewer中的，所以如果其子控件超出了一定范围，其子控件外面是会显示滚动条的。

　　2.2 FormItem

　　FormItem是从ListBoxItem继承而来，而ListBoxItem又是从ContentControl继承而来的，所以可以添加到任何具有Content属性的控件中去，常见的ListBoxItem可以放到ListBox中，也可以放到ItemsControl中去，ListBoxItem可以横向和TreeViewItem进行比较，只不过TreeViewItem是直接从HeaderedItemsControl继承过来的，然后再继承自ItemsControl。两者有很多的共同之处，可以做更多的横向比较，我们今天只是来讲ListBoxItem，首先看看我们使用的样式，这里贴出前端代码：


<Style TargetType="local:FormItem">
        <Setter Property="Margin" Value="0 0 0 15"></Setter>
        <Setter Property="Background" Value="#fff"></Setter>
        <Setter Property="Height" Value="50"></Setter>
        <Setter Property="HorizontalAlignment" Value="Stretch"></Setter>
        <Setter Property="VerticalAlignment" Value="Stretch"></Setter>
        <Setter Property="Padding" Value="6"></Setter>
        <Setter Property="Foreground" Value="{StaticResource DarkColor}"></Setter>
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="local:FormItem">
                    <Grid Background="{TemplateBinding Background}" Height="{TemplateBinding Height}">
                        <Grid.ColumnDefinitions>
                            <ColumnDefinition Width="{Binding HeaderWidth,RelativeSource={RelativeSource Mode=FindAncestor,AncestorType=local:Form}}"></ColumnDefinition>
                            <ColumnDefinition Width="*"></ColumnDefinition>
                        </Grid.ColumnDefinitions>
                        <Rectangle Width="3" HorizontalAlignment="Left" Fill="{StaticResource Highlight}"></Rectangle>
                        <StackPanel VerticalAlignment="Center" HorizontalAlignment="Left" Margin="13 0 0 0" Orientation="Horizontal">
                            <Image x:Name="Icon" Source="{TemplateBinding Icon}" Width="24" Height="24" Margin="0 0 10 0" VerticalAlignment="Center" HorizontalAlignment="Left"></Image>
                            <TextBlock Text="{TemplateBinding Title}" Foreground="{TemplateBinding Foreground}" VerticalAlignment="Center" HorizontalAlignment="Left"></TextBlock>
                        </StackPanel>
                        <ContentPresenter Margin="{TemplateBinding Padding}" Grid.Column="1" HorizontalAlignment="{TemplateBinding HorizontalAlignment}" VerticalAlignment="{TemplateBinding VerticalAlignment}"></ContentPresenter>
                    </Grid>
                    <ControlTemplate.Triggers>
                        <Trigger Property="Icon" Value="{x:Null}">
                            <Setter Property="Visibility" Value="Collapsed" TargetName="Icon"></Setter>
                        </Trigger>
                    </ControlTemplate.Triggers>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>

　　这里我们重写了ListBoxItem 的ControlTemplate，我们需要注意的一个地方就是我们使用了


<ContentPresenter Margin="{TemplateBinding Padding}" Grid.Column="1" HorizontalAlignment="{TemplateBinding HorizontalAlignment}" VerticalAlignment="{TemplateBinding VerticalAlignment}"></ContentPresenter>

来替代ListBoxItem的Content，我们需要始终记住，只有控件拥有Content属性才能使用ContentPresenter ，这个属性是用来呈现控件的Content。

另外一个需要重点介绍的就是FormItem这个类中的代码，这个控件在加载的时候所有的效果都是在后台中进行加载的，首先贴出相关的类的实现，然后再做进一步的分析。


using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Media;
using System.Windows.Media.Animation;
 
namespace X.UI
{
    public class FormItem : ListBoxItem
    {
        static FormItem()
        {
            DefaultStyleKeyProperty.OverrideMetadata(typeof(FormItem), new FrameworkPropertyMetadata(typeof(FormItem)));          
        }
 
        public FormItem()
        {
            System.Windows.Media.TranslateTransform transform = EnsureRenderTransform<System.Windows.Media.TranslateTransform>(this);
            transform.X = transform.Y = 100;
            Opacity = 0;
 
            IsVisibleChanged += FormItem_IsVisibleChanged;
        }
 
        void FormItem_IsVisibleChanged(object sender, DependencyPropertyChangedEventArgs e)
        {
            if (this.Parent is Form)
            {
                if (!IsVisible)
                {
                    int index = (this.Parent as Form).Items.IndexOf(this);
                    System.Windows.Media.TranslateTransform transform = EnsureRenderTransform<System.Windows.Media.TranslateTransform>(this);
                    DoubleAnimation da = new DoubleAnimation()
                    {
                        From = 0,
                        To = 100,
                        EasingFunction = new CircleEase { EasingMode = EasingMode.EaseOut }
                    };
                    transform.BeginAnimation(System.Windows.Media.TranslateTransform.XProperty, da);
                    transform.BeginAnimation(System.Windows.Media.TranslateTransform.YProperty, da);
                    DoubleAnimation daopacity = new DoubleAnimation
                    {
                        From = 1,
                        To = 0,
                    };
                    this.BeginAnimation(UIElement.OpacityProperty, daopacity);
                }
                else
                {
                    int index = (this.Parent as Form).Items.IndexOf(this);
                    System.Windows.Media.TranslateTransform transform = EnsureRenderTransform<System.Windows.Media.TranslateTransform>(this);
                    DoubleAnimation da = new DoubleAnimation()
                    {
                        From = 100,
                        To = 0,
                        BeginTime = TimeSpan.FromMilliseconds(100 * (index + 1)),
                        Duration = TimeSpan.FromMilliseconds(666),
                        EasingFunction = new CircleEase { EasingMode = EasingMode.EaseOut }
                    };
                    transform.BeginAnimation(System.Windows.Media.TranslateTransform.XProperty, da);
                    transform.BeginAnimation(System.Windows.Media.TranslateTransform.YProperty, da);
                    DoubleAnimation daopacity = new DoubleAnimation
                    {
                        From = 0,
                        To = 1,
                        BeginTime = TimeSpan.FromMilliseconds(100 * (index + 1)),
                        Duration = TimeSpan.FromMilliseconds(666),
                        EasingFunction = new CircleEase { EasingMode = EasingMode.EaseOut }
                    };
                    this.BeginAnimation(UIElement.OpacityProperty, daopacity);
                }
            }
        }
 
        private T EnsureRenderTransform<T>(UIElement uiTarget)
            where T : Transform
        {
            if (uiTarget.RenderTransform is T)
                return uiTarget.RenderTransform as T;
            else
            {
                T instance = typeof(T).Assembly.CreateInstance(typeof(T).FullName) as T;
                uiTarget.RenderTransform = instance;
                return instance;
            }
        }
 
        public string Title
        {
            get { return (string)GetValue(TitleProperty); }
            set { SetValue(TitleProperty, value); }
        }
 
        // Using a DependencyProperty as the backing store for Title.  This enables animation, styling, binding, etc...
        public static readonly DependencyProperty TitleProperty =
            DependencyProperty.Register("Title", typeof(string), typeof(FormItem), new PropertyMetadata(""));
 
 
        public ImageSource Icon
        {
            get { return (ImageSource)GetValue(IconProperty); }
            set { SetValue(IconProperty, value); }
        }
 
        // Using a DependencyProperty as the backing store for Icon.  This enables animation, styling, binding, etc...
        public static readonly DependencyProperty IconProperty =
            DependencyProperty.Register("Icon", typeof(ImageSource), typeof(FormItem), new PropertyMetadata(null));
 
    }
}

这里在FormItem的构造函数中，添加了一个IsVisibleChanged事件，这个事件会在加载当前控件的时候发生，另外当当前控件的属性值发生变化的时候会触发该效果。其实效果就是同时在X和Y方向做一个平移的效果，这个也是一个常用的效果。

我们重点讨论的是下面的这段代码：


private T EnsureRenderTransform<T>(UIElement uiTarget)
           where T : Transform
       {
           if (uiTarget.RenderTransform is T)
               return uiTarget.RenderTransform as T;
           else
           {
               T instance = typeof(T).Assembly.CreateInstance(typeof(T).FullName) as T;
               uiTarget.RenderTransform = instance;
               return instance;
           }
       }

　　这里我们创建TranslateTransform的时候是使用的System.Windows.Media.TranslateTransform transform = EnsureRenderTransform<System.Windows.Media.TranslateTransform>(this);这个方法，而不是每次都new一个对象，每次new一个对象的效率是很低的，而且会占据内存，我们如果已经创建过当前对象完全可以重复利用，这里我们使用了带泛型参数的函数来实现当前效果，typeof(T).Assembly.CreateInstance(typeof(T).FullName) as T，核心是通过程序集来创建对象，这种方式我们也是经常会使用的，比如我们可以通过获取应用程序级别的程序集来通过Activator.CreateInstance来创建窗体等一系列的对象，这种通过反射的机制来扩展的方法是我们需要特别留意的，另外写代码的时候必须注重代码的质量和效率，而不仅仅是实现了某一个功能，这个在以后的开发过程中再一点点去积累去吸收。

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