Silverlight - 回车键触发默认按钮

一个常见的需求是，用户在某个TextBox中输入回车键，自动触发界面上的某个按钮。比如登录窗口中，用户输入完密码后按回车，自动触发登录按钮。

Silverlight (4.0)目前还没有像winform程序那样可通过设置一个属性值来简单实现。

Patrick Cauldweel 提供了一个方案， Kyle Burns 做了些改进，增加了通用性，并解决了前者的一些缺点。

受Kyle启发，我的实现方法是实现为一个Panel(Grid,Canvas,StackPanel的基类)控件的Behavior。该实现需要引用System.Windows.Interactivity.dll

一个示例登录窗口的Xaml如下：

<StackPanel>

<i:Interaction.Behaviors>

<command:DefaultButtonBehaviorDefaultButtonName="{BindingElementName=btnLogin,Path=Name}"/>

</i:Interaction.Behaviors>

<TextBox Text="{Binding LoginName}"/>

<PasswordBox Password="{Binding LoginPassword}"/>

<Button Content="Login" x:Name="btnLogin" Command="{Binding LoginCommand}"/>

</StackPanel>

DefaultButtonBehavior类(vb.net):

ImportsSystem.Windows.Interactivity
ImportsSystem.Windows.Data
ImportsSystem.Windows.Automation.Peers
ImportsSystem.Windows.Automation.Provider
ImportsSystem.Linq
 
NamespaceCommands
 
PublicClassDefaultButtonBehavior
InheritsBehavior(OfPanel)
 
PublicPropertyDefaultButtonNameAsString
Get
ReturnCType(GetValue(DefaultButtonNameProperty),String)
EndGet
Set(ByValvalueAsString)
SetValue(DefaultButtonNameProperty,value)
EndSet
EndProperty
 
PublicSharedReadOnlyDefaultButtonNamePropertyAsDependencyProperty_
=DependencyProperty.Register(name:="DefaultButtonName",_
propertyType:=GetType(String),_
ownerType:=GetType(DefaultButtonBehavior),_
typeMetadata:=Nothing)
 
ProtectedOverridesSubOnAttached()
MyBase.OnAttached()
AddHandlerAssociatedObject.KeyUp,AddressOfAssociatedObject_KeyUp
EndSub
 
ProtectedOverridesSubOnDetaching()
MyBase.OnDetaching()
RemoveHandlerAssociatedObject.KeyUp,AddressOfAssociatedObject_KeyUp
EndSub
 
PrivateSubAssociatedObject_KeyUp(ByValsenderAsObject,ByValeAsKeyEventArgs)
Ife.Key=Key.EnterThen
 
DimdefaultButtonAsButton=AssociatedObject.Children.OfType(OfButton).FirstOrDefault(Function(x)x.Name=DefaultButtonName)
IfdefaultButtonIsNotNothingAnddefaultButton.IsEnabledThen
 
'updatebindingsourceofTextBox
DiminputTxts=AssociatedObject.Children.OfType(OfTextBox)()
ForEachtxtIninputTxts
DimexpAsBindingExpression=txt.GetBindingExpression(TextBox.TextProperty)
exp.UpdateSource()
Next
 
'updatebindingsourceofPassword
DiminputPwds=AssociatedObject.Children.OfType(OfPasswordBox)()
ForEachpwdIninputPwds
DimexpAsBindingExpression=pwd.GetBindingExpression(PasswordBox.PasswordProperty)
exp.UpdateSource()
Next
 
DimpeerAsNewButtonAutomationPeer(defaultButton)
DiminvokeAsIInvokeProvider=peer.GetPattern(PatternInterface.Invoke)
invoke.Invoke()
e.Handled=True
EndIf

EndIf
EndSub
 
EndClass
 
EndNamespace