首先說明了屬性的現存問題,然後介紹了依賴屬性的基本用法及其解決方案,由於依賴屬性以靜態屬性的方式存在,進而又介紹了可重寫的屬性元數據的使用.這是以上三篇所說明的問題.當然依賴屬性的特性依然沒有說完整.這兩天也一直在想依賴屬性,然後就是頭疼,呵呵.由於WPF的依賴屬性系統與整體功能都有關聯,所以接下來等講到某個特性的時候然後再來講依賴屬性.這篇我們來個簡單的實踐,增加點樂趣.
定義RadioButtonList和CheckBoxList
WPF內置沒有這兩個控件,但實際開發時,用到的會比較多.下面我們一起來創建這兩個控件.
- 明確控件需求
- 定義依賴屬性
- 重寫默認樣式屬性元數據
- 用xaml定義控件樣式
一.明確控件需求
控件功能如下:
- 可以垂直,水平排列
- 可以分行,列
- 爲子項設置Margin
二.定義依賴屬性
爲避免重複定義屬性，爲兩個控件定義公共類ListControl,從ListBox繼承
然後定義依賴屬性
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))); } }
以上依賴屬性定義的非常簡單,之所以定義成依賴屬性是因爲可以進行屬性綁定操作.
三.重寫默認樣式屬性元數據
/// <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定義控件樣式
默認項目中會有一個Generic.xaml文件,我們要把樣式定義在此文件中
控件樣式定義
(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,到這裏就完事了.我們發現我們並不需要寫多少代碼,就可以實現一個控件.而且RadioButtonList和CheckBoxList幾乎沒有代碼,僅僅只是重寫了樣式而已,這也是WPF定義控件的基本概念,一些變的都是如此簡單.