wpf 控件开发基础(6) -单一容器(Decorator)

   其实这部分的文章已经很多了,写下来方便自己查询.

wpf内置提供了很多容器(Panel),容器分为多容器和单容器.下面介绍单容器.内置的单容器,大家最熟悉的如Border,其作用用于装饰容器内的元素,单一容器继承自Decorator,下面来看一个未使用装饰器的例子.

 

<Window x:Class="WPFControlTutorialPart6_WPFApp.Window1"    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"    xmlns:control="clr-namespace:WPF.Controls;assembly=WPF.Controls"    Title="Window1" Height="300" Width="300">    <Grid>            <Button>Hello World</Button>    </Grid></Window>

可以看到一个Button控件填充了整个窗体。一般我们只需要显示正常大小的Button即可.

容器计算规则

计算容器的大小是一个递归的过程,永远是先测量(MeasureOverride)子元素,然后通知父元素分配空间.计算好空间后然后排列(ArrangeOverride),如果测量大小过度ArrangeOverride会自动进行修正的.自定义一个单容器来修正上面的布局

public class PixelSnapper : Decorator{    protected override Size ArrangeOverride(Size finalSize)    {        Point location = this.CalculateOffset(finalSize, this.Child);        location.X = Math.Round(location.X);        location.Y = Math.Round(location.Y);        this.Child.Arrange(new Rect(location, this.Child.DesiredSize));        return finalSize;    }    private Point CalculateOffset(Size finalSize, UIElement ui)    {        Point point = new Point(0.0, 0.0);        if (ui is FrameworkElement)        {            FrameworkElement element = ui as FrameworkElement;            Size desiredSize = element.DesiredSize;            switch (element.HorizontalAlignment)            {                case HorizontalAlignment.Left:                    point.X = element.Margin.Left;                    break;                case HorizontalAlignment.Center:                    point.X = (((finalSize.Width - desiredSize.Width) + base.Margin.Left) - base.Margin.Right) / 2.0;                    break;                case HorizontalAlignment.Right:                    point.X = (finalSize.Width - element.Margin.Right) - desiredSize.Width;                    break;            }            switch (element.VerticalAlignment)            {                case VerticalAlignment.Top:                    point.Y = element.Margin.Top;                    return point;                case VerticalAlignment.Center:                    point.Y = (((finalSize.Height - desiredSize.Height) + base.Margin.Top) - base.Margin.Bottom) / 2.0;                    return point;                case VerticalAlignment.Bottom:                    point.Y = (finalSize.Height - element.Margin.Bottom) - desiredSize.Height;                    return point;            }        }        return point;    }}

现在布局

wpf内置的BulletDecorator.如内置的CheckBox和RadioButton都是BulletDecorator,左边是符号,右侧是Content

示例