如何根据 WP7 上的属性值更改 VisualState?
我尝试使用 MVVM 模式,当我的模型加载时,我希望我的 View 转到特定的 VisualState。
在 Silverlight 中,我们有属性更改的触发器,但在 WP7 中没有!
PS:我不想使用框架我想了解它是如何在 WP7 中完成的。
最佳答案
我使用以下附加行为:
using System;
using System.Windows;
using System.Windows.Controls;
namespace PixelLab.WP7.Common.Behaviors
{
///
/// Provides an attached behavior for binding visual states.
///
public static class VisualStates
{
///
/// Identifies the CurrentState attached property.
///
public static readonly DependencyProperty CurrentStateProperty = DependencyProperty
.RegisterAttached(
"CurrentState",
typeof(string),
typeof(VisualStates),
new PropertyMetadata(TransitionToState));
///
/// Gets the current visual state of the specified object. This is an attached property.
///
/// The source object.
/// The current visual state of the specified object.
public static string GetCurrentState(DependencyObject obj)
{
return (string)obj.GetValue(CurrentStateProperty);
}
///
/// Sets the current visual state of the specified object. This is an attached property.
///
/// The target object.
/// The new visual state.
public static void SetCurrentState(DependencyObject obj, string value)
{
obj.SetValue(CurrentStateProperty, value);
}
static void startOnGuiThread( Action act )
{
var disp = Deployment.Current.Dispatcher;
if( disp.CheckAccess() )
act();
else
disp.BeginInvoke( act );
}
private static void TransitionToState( object sender, DependencyPropertyChangedEventArgs args )
{
FrameworkElement elt = sender as FrameworkElement;
if( null == elt )
throw new ArgumentException( "CurrentState is only supported on the FrameworkElement" );
string newState = args.NewValue.ToString();
startOnGuiThread( () => ExtendedVisualStateManager.GoToElementState( elt, newState, true ) );
}
}
}
在您的 View 模型中,公开当前视觉状态的属性,然后在要为您处理视觉状态的视觉元素上使用以下内容绑定(bind)视觉状态,例如
<phone:PhoneApplicationPage ...
xmlns:common="clr-namespace:PixelLab.Common;assembly=PixelLab.Common"
common:VisualStates.CurrentState="{Binding CurrentState}">
关于silverlight - 根据属性值更改 VisualState,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/5008625/