wpf控件开发基础(5) -依赖属性实践

知识回顾

接上篇,回顾这三篇讲了什么东西

首先说明了属性的现存问题,然后介绍了依赖属性的基本用法及其解决方案,由于依赖属性以静态属性的方式存在,进而又介绍了可重写的属性元数据的使用.这是以上三篇所说明的问题.当然依赖属性的特性依然没有说完整.这两天也一直在想依赖属性,然后就是头疼,呵呵.由于WPF的依赖属性系统与整体功能都有关联,所以接下来等讲到某个特性的时候然后再来讲依赖属性.这篇我们来个简单的实践,增加点乐趣.

定义RadioButtonList和CheckBoxList

WPF内置没有这两个控件,但实际开发时,用到的会比较多.下面我们一起来创建这两个控件.

1. 明确控件需求
2. 定义依赖属性
3. 重写默认样式属性元数据
4. 用xaml定义控件样式

一.明确控件需求

控件功能如下:

1. 可以垂直,水平排列
2. 可以分行,列
3. 为子项设置Margin

二.定义依赖属性

为避免重复定义属性，为两个控件定义公共类ListControl,从ListBox继承

然后定义依赖属性

namespace WPF.Controls{    /// <summary>    /// this is a base class for CheckBoxList and RadioButtonList    /// this class define some common property    /// </summary>    public abstract class ListControl : ListBox    {        #region Orientation        /// <summary>        /// Gets or sets a value that indicates the dimension by which child elements are stacked.        /// This is a dependency property.        /// </summary>        public Orientation Orientation        {            get { return (Orientation)GetValue(OrientationProperty); }            set { SetValue(OrientationProperty, value); }        }        public static readonly DependencyProperty OrientationProperty =            DependencyProperty.Register("Orientation", typeof(Orientation), typeof(ListControl),            new UIPropertyMetadata(Orientation.Vertical, new PropertyChangedCallback(OrientationChangedCallback)));        public static void OrientationChangedCallback(DependencyObject d, DependencyPropertyChangedEventArgs e)        {            ListControl control = d as ListControl;            if (control.Orientation == Orientation.Horizontal)            {                control.Columns = 0;                control.Rows = 1;            }            else if (control.Orientation == Orientation.Vertical)            {                control.Rows = 0;                control.Columns = 1;            }        }        #endregion        #region Columns        /// <summary>        /// Get or set a value that indicates which Columns list item should appear in.        /// This is a dependency property.        /// </summary>        public int Columns        {            get { return (int)GetValue(ColumnsProperty); }            set { SetValue(ColumnsProperty, value); }        }        public static readonly DependencyProperty ColumnsProperty =            DependencyProperty.Register("Columns", typeof(int), typeof(ListControl), new UIPropertyMetadata(1));        #endregion        #region Rows        /// <summary>        /// Get or set a value that indicates which Rows list item should appear in.        /// This is a dependency property.        /// </summary>        public int Rows        {            get { return (int)GetValue(RowsProperty); }            set { SetValue(RowsProperty, value); }        }        public static readonly DependencyProperty RowsProperty =            DependencyProperty.Register("Rows", typeof(int), typeof(ListControl), new UIPropertyMetadata(0));        #endregion        public Thickness SubMargin        {            get { return (Thickness)GetValue(SubMarginProperty); }            set { SetValue(SubMarginProperty, value); }        }        public static readonly DependencyProperty SubMarginProperty =            DependencyProperty.Register("SubMargin", typeof(Thickness), typeof(ListControl),             new UIPropertyMetadata(new Thickness(2,2,2,0)));    }}

以上依赖属性定义的非常简单,之所以定义成依赖属性是因为可以进行属性绑定操作.

三.重写默认样式属性元数据

/// <summary>/// Represents a control that a user can choose one from list options in a group radiobutton/// </summary>public class RadioButtonList : ListControl{    static RadioButtonList()    {        DefaultStyleKeyProperty.OverrideMetadata(typeof(RadioButtonList)            , new FrameworkPropertyMetadata(typeof(RadioButtonList)));    }}/// <summary>/// Contains a list of selectable CheckBox items /// Represents a control that a user can choose from a list options in a group of CheckBox/// </summary>public class CheckBoxList : ListControl{    static CheckBoxList()    {        DefaultStyleKeyProperty.OverrideMetadata(typeof(CheckBoxList)            , new FrameworkPropertyMetadata(typeof(CheckBoxList)));    }}

四.用xaml定义控件样式

默认项目中会有一个Generic.xaml文件,我们要把样式定义在此文件中

控件样式定义

(1)ListControl

<Style TargetType="{x:Type local:ListControl}" BasedOn="{StaticResource {x:Type ListBox}}">    <Setter Property="ItemsPanel">        <Setter.Value>            <ItemsPanelTemplate>                <UniformGrid HorizontalAlignment="Left" VerticalAlignment="Top"                    Rows="{Binding Path=Rows,RelativeSource={RelativeSource FindAncestor,AncestorType={x:Type local:ListControl}}}"                     Columns="{Binding Path=Columns,RelativeSource={RelativeSource FindAncestor,AncestorType={x:Type local:ListControl}}}"></UniformGrid>            </ItemsPanelTemplate>        </Setter.Value>    </Setter>    <Setter Property="BorderThickness" Value="0" />    <Setter Property="Background" Value="Transparent" /></Style>

(2)RadioButtonList

<Style TargetType="{x:Type local:RadioButtonList}" BasedOn="{StaticResource {x:Type local:ListControl}}">    <Style.Resources>        <Style TargetType="ListBoxItem">            <Setter Property="Margin" Value="2, 2, 2, 0" />            <Setter Property="Template">                <Setter.Value>                    <ControlTemplate TargetType="ListBoxItem">                            <RadioButton                                 Margin="{Binding Path=SubMargin,RelativeSource={RelativeSource FindAncestor,AncestorType={x:Type local:RadioButtonList}}}"                                IsChecked="{Binding IsSelected, RelativeSource={RelativeSource TemplatedParent},Mode=TwoWay}">                                <RadioButton.Content>                                    <ContentPresenter/>                                </RadioButton.Content>                            </RadioButton>                    </ControlTemplate>                </Setter.Value>            </Setter>        </Style>    </Style.Resources></Style>

(3)CheckBoxList

<Style TargetType="{x:Type local:CheckBoxList}" BasedOn="{StaticResource {x:Type local:ListControl}}">    <Setter Property="SelectionMode" Value="Multiple"></Setter>    <Style.Resources>        <Style TargetType="ListBoxItem">            <Setter Property="Margin" Value="2, 2, 2, 0" />            <Setter Property="Template">                <Setter.Value>                    <ControlTemplate TargetType="ListBoxItem">                            <CheckBox                                Margin="{Binding Path=SubMargin,RelativeSource={RelativeSource FindAncestor,AncestorType={x:Type local:RadioButtonList}}}"                                IsChecked="{Binding IsSelected, RelativeSource={RelativeSource TemplatedParent},Mode=TwoWay}">                                <CheckBox.Content>                                    <ContentPresenter/>                                </CheckBox.Content>                            </CheckBox>                    </ControlTemplate>                </Setter.Value>            </Setter>        </Style>    </Style.Resources></Style>

OK,到这里就完事了.我们发现我们并不需要写多少代码,就可以实现一个控件.而且RadioButtonList和CheckBoxList几乎没有代码,仅仅只是重写了样式而已,这也是WPF定义控件的基本概念,一些变的都是如此简单.

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