如何在Silverlight 4中等待状态转换完成?

时间:2010-09-06 17:56:09

标签: c# wpf silverlight silverlight-4.0 visualstatemanager

我需要更改控件的状态然后执行一些操作。具体来说,我想在隐藏控件之前运行动画。我想做那样的事情:

VisualStateManager.GoToState(control, "Hidden", true); // wait until the transition animation is finished
ParentControl.Children.Remove(control);

问题是过渡动画是异步运行的,因此在动画启动后立即从可视树中删除控件。

那我该如何等待动画完成呢?

3 个答案:

答案 0 :(得分:14)

您可以将Storyboard.Completed事件处理程序附加到Storyboard,或将VisualStateGroup.CurrentStateChanged事件处理程序附加到VisualStateGroup:

<UserControl
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" mc:Ignorable="d"
x:Class="SilverlightApplication7.MainPage"
Width="640" Height="480">

<Grid x:Name="LayoutRoot" Background="White">
    <VisualStateManager.VisualStateGroups>
        <VisualStateGroup x:Name="VisualStateGroup" >
            <VisualState x:Name="Hidden">
                <Storyboard Completed="OnHidden">
                    <DoubleAnimation Duration="0" To="1" Storyboard.TargetProperty="(UIElement.Opacity)" Storyboard.TargetName="rectangle" d:IsOptimized="True"/>
                </Storyboard>
            </VisualState>
        </VisualStateGroup>
    </VisualStateManager.VisualStateGroups>
    <Rectangle x:Name="rectangle" Fill="#FFF4F4F5" HorizontalAlignment="Left" Height="136" Margin="48,72,0,0" Opacity="0" Stroke="Black" VerticalAlignment="Top" Width="208"/>
</Grid>

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;

namespace SilverlightApplication7
{
public partial class MainPage : UserControl
{
    public MainPage()
    {
        // Required to initialize variables
        InitializeComponent();

        this.Loaded += new RoutedEventHandler(MainPage_Loaded);
    }

    void MainPage_Loaded(object sender, RoutedEventArgs e)
    {
        VisualStateManager.GoToState(this, "Hidden", true);
    }

    private void OnHidden(object storyboard, EventArgs args)
    {

    }
}

}

答案 1 :(得分:3)

处理此问题的正确方法是在VisualStateGroup上侦听CurrentStateChanged事件,但根据我的经验,它最多不可靠并且在最坏情况下会被破坏。

第二个选项是在Storyboard上挂钩Completed事件,但是这个选项有自己的缺陷。在某些情况下,可视状态管理器会在内部生成动画,因此您设置的已完成事件将不会被调用。

答案 2 :(得分:3)

事实上,可以在代码中附加Completed处理程序:

Collection<VisualStateGroup> grps = (Collection<VisualStateGroup>)VisualStateManager.GetVisualStateGroups(this.LayoutRoot);
foreach (VisualStateGroup grp in grps) {
    Collection<VisualState> states = (Collection<VisualState>)grp.States;
    foreach (VisualState state in states) {
        switch (state.Name) {
            case "Intro":
            state.Storyboard.Completed += new EventHandler(Intro_Completed);break;
        }
    }
}

此主题的示例:http://forums.silverlight.net/forums/p/38027/276746.aspx

使用附加行为为我在实时项目中工作!虽然我不得不为根UserControl(在VisualStateManager.GoToState中使用)和LayoutRoot使用单独的依赖属性来获取实际的VisualStateGroup集合,但有点烦人。