Question

我想确保控件在最短的时间内保持在某种状态。该控件有两种状态：Loading和Loaded。 Loading状态显示动画，Loaded状态显示数据。两个州之间有一个淡入/淡出过渡。

然而，问题是有时数据加载速度太快，以至于动画暂时在屏幕上轻弹，然后立即淡出。这看起来很糟糕，所以我想做的是在Loading状态下花费最少的时间（例如半秒）。这样，即使数据加载速度很快，加载动画也至少会显示足够长的时间而不会产生刺耳的效果。

我设法使用我想象中称为VisualStateManager的自定义MinimumTimeVisualStateManager来实现此目标。但是，我想知道是否有一种内置的方法来实现我想要的，而不需要这些额外的代码。

由于

Answer 1

这是我的解决方案：

// a VisualStateManager that can impose minimum times that a control is in a particular state
public class MinimumTimeVisualStateManager : VisualStateManager
{
    public static readonly DependencyProperty MinimumTimeProperty = DependencyProperty.RegisterAttached("MinimumTime",
        typeof(TimeSpan),
        typeof(MinimumTimeVisualStateManager),
        new PropertyMetadata(TimeSpan.Zero));

    private static readonly DependencyProperty StateChangeMinimumTimeProperty = DependencyProperty.RegisterAttached("StateChangeMinimumTime",
        typeof(DateTime),
        typeof(MinimumTimeVisualStateManager),
        new PropertyMetadata(DateTime.MinValue));

    public static TimeSpan GetMinimumTime(VisualState visualState)
    {
        visualState.AssertNotNull("visualState");
        return (TimeSpan)visualState.GetValue(MinimumTimeProperty);
    }

    public static void SetMinimumTime(VisualState visualState, TimeSpan minimumTime)
    {
        visualState.AssertNotNull("visualState");
        visualState.SetValue(MinimumTimeProperty, minimumTime);
    }

    private static DateTime GetStateChangeMinimumTime(Control control)
    {
        control.AssertNotNull("control");
        return (DateTime)control.GetValue(StateChangeMinimumTimeProperty);
    }

    private static void SetStateChangeMinimumTime(Control control, DateTime stateChangeMinimumTime)
    {
        control.AssertNotNull("control");
        control.SetValue(StateChangeMinimumTimeProperty, stateChangeMinimumTime);
    }

    protected override bool GoToStateCore(Control control, FrameworkElement templateRoot, string stateName, VisualStateGroup group, VisualState state, bool useTransitions)
    {
        var minimumTimeToStateChange = GetStateChangeMinimumTime(control);

        if (DateTime.UtcNow < minimumTimeToStateChange)
        {
            // can't transition yet so reschedule for later
            var dispatcherTimer = new DispatcherTimer();
            dispatcherTimer.Interval = minimumTimeToStateChange - DateTime.UtcNow;
            dispatcherTimer.Tick += delegate
            {
                dispatcherTimer.Stop();
                this.DoStateChange(control, templateRoot, stateName, group, state, useTransitions);
            };
            dispatcherTimer.Start();

            return false;
        }

        return this.DoStateChange(control, templateRoot, stateName, group, state, useTransitions);
    }

    private bool DoStateChange(Control control, FrameworkElement templateRoot, string stateName, VisualStateGroup group, VisualState state, bool useTransitions)
    {
        var succeeded = base.GoToStateCore(control, templateRoot, stateName, group, state, useTransitions);

        if (succeeded)
        {
            SetStateChangeMinimumTime(control, DateTime.MinValue);
            var minimumTimeInState = GetMinimumTime(state);

            if (minimumTimeInState > TimeSpan.Zero)
            {
                SetStateChangeMinimumTime(control, DateTime.UtcNow + minimumTimeInState);
            }
        }

        return succeeded;
    }
}

它的用法如下：

<VisualStateManager.VisualStateGroups>
    <VisualStateGroup x:Name="Modes">
        <VisualState x:Name="Loading" local:MinimumTimeVisualStateManager.MinimumTime="0:00:0.5"/>

        <VisualState x:Name="Loaded">
            <Storyboard>
                <!-- omitted for clarity -->
            </Storyboard>
        </VisualState>
    </VisualStateGroup>
</VisualStateManager.VisualStateGroups>

它似乎工作正常，但我希望这是我可以删除的代码。

肯特

在给定的视觉状态下花费最少的时间

1 个答案: