bri*_*rns 3 wpf xaml f# mvvm fsxaml
我想绑定到使用FsXaml和FSharp.ViewModule构建的MVVM F#应用程序中的WPF TextBox.我在此处描述的应用程序中添加了一个名为"SetA"的命令,并尝试使用以下XAML绑定到它:
<TextBox Text="{Binding Score.ScoreA, Mode=OneWay}" FontFamily="Lucida Console">
<i:Interaction.Triggers>
<i:EventTrigger EventName="TextChanged">
<fsx:EventToCommand Command="{Binding SetA}" />
</i:EventTrigger>
</i:Interaction.Triggers>
</TextBox>
从ScoreA属性正确填充TextBox,但是当我在TextBox中键入新值时,不会调用SetA命令.我对F#很满意,但这是我的第一个WPF MVVM应用程序,所以我不确定我做错了什么.当用户更改文本值时,如何触发我的SetA处理程序？
这是我的ViewModel:
type MainViewModel(controller : Score -> ScoringEvent -> Score) as self =
inherit EventViewModelBase<ScoringEvent>()
let score = self.Factory.Backing(<@ self.Score @>, Score.zero)
let eventHandler ev =
score.Value <- controller score.Value ev
do
self.EventStream
|> Observable.add eventHandler
member this.IncA = this.Factory.EventValueCommand(IncA)
member this.DecA = this.Factory.EventValueCommandChecked(DecA, (fun _ -> this.Score.ScoreA > 0), [ <@@ this.Score @@> ])
member this.IncB = this.Factory.EventValueCommand(IncB)
member this.DecB = this.Factory.EventValueCommandChecked(DecB, (fun _ -> this.Score.ScoreB > 0), [ <@@ this.Score @@> ])
member this.NewGame = this.Factory.EventValueCommand(New)
member this.SetA = this.Factory.EventValueCommand(SetA)
member __.Score = score.Value
我只添加了定义SetA的一行.
最有可能的Command是被召唤,但结果并不是你所期望的.
出于测试目的尝试
member this.SetA =
this.Factory.CommandSync(
fun _ -> System.Windows.MessageBox.Show("TextChanged","RoutedEv") |> ignore)
请注意CommandSync而不是EventValueCommand.无论你如何改变分数,都会弹出一个msgbox.
你也可以保留 EventValueCommand
member this.SetA = this.Factory.EventValueCommand(SetA)
并在update乐趣中做同样的事情
let update score event =
match event with
| IncA -> {score with ScoreA = score.ScoreA + 1}
| DecA -> {score with ScoreA = max (score.ScoreA - 1) 0}
| IncB -> {score with ScoreB = score.ScoreB + 1}
| DecB -> {score with ScoreB = max (score.ScoreB - 1) 0}
| New -> zero
| SetA -> System.Windows.MessageBox.Show("TextChanged","RoutedEv") |> ignore ; score
回到不是你期望的部分,我假设你希望在更改TextBox.Text值时更新记分板中的分数.
正如你所注意到的那样,没有(纯粹的)方法可以使用当前的TextBox.Text价值将价值带入update乐趣中controller.由于SetX行为未得到修复,因此与IncX,DecX或New事件的情况不同.
选项:
您可以将控制器的签名更改为Score -> ScoringEvent -> string option -> Score并使用选项值来处理update有趣的SetX事件.
你可以处理一切ViewModel.记录的不变性强迫使用a OneWay Binding.我会保持它不可变,但你可以(de)组成ViewModel中的所有内容.
尝试
视图模型
type MainViewModel(controller : Score -> ScoringEvent -> Score) as self =
inherit EventViewModelBase<ScoringEvent>()
let scoreA = self.Factory.Backing(<@ self.ScoreA @>, 0)
let scoreB = self.Factory.Backing(<@ self.ScoreB @>, 0)
let updateVM score =
scoreA.Value <- score.ScoreA
scoreB.Value <- score.ScoreB
let eventHandler ev =
updateVM <| controller {ScoreA = scoreA.Value ; ScoreB = scoreB.Value} ev
do
self.EventStream
|> Observable.add eventHandler
member this.IncA = this.Factory.EventValueCommand(IncA)
member this.DecA = this.Factory.EventValueCommandChecked(DecA, (fun _ -> this.ScoreA > 0), [ <@@ this.ScoreA @@> ])
member this.IncB = this.Factory.EventValueCommand(IncB)
member this.DecB = this.Factory.EventValueCommandChecked(DecB, (fun _ -> this.ScoreB > 0), [ <@@ this.ScoreB @@> ])
member this.NewGame = this.Factory.EventValueCommand(New)
member __.ScoreA
with get() = scoreA.Value
and set v = scoreA.Value <- v
member __.ScoreB
with get() = scoreB.Value
and set v = scoreB.Value <- v
XAML
<DockPanel LastChildFill="True">
<StackPanel DockPanel.Dock="Bottom" Height="75" Orientation="Horizontal" Background="#FF3A3A3A">
<Button Height="70" Width="70" Margin="2" Command="{Binding NewGame}">
<TextBlock Text="New" FontSize="18"></TextBlock>
</Button>
<TextBox Text="{Binding ScoreA, UpdateSourceTrigger=PropertyChanged}"
Margin="2" FontSize="18" HorizontalContentAlignment="Center" VerticalContentAlignment="Center">
</TextBox>
</StackPanel>
<Grid>
<Grid.RowDefinitions>
<RowDefinition />
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition />
<ColumnDefinition />
</Grid.ColumnDefinitions>
<Border Background="#FF024D70" Grid.Column="0">
<Grid>
<Viewbox>
<Label Content="{Binding ScoreA}" ContentStringFormat="D2" FontFamily="Lucida Console"></Label>
</Viewbox>
<StackPanel Orientation="Horizontal" HorizontalAlignment="Center">
<Button Command="{Binding DecA}" Height="70" Width="70" VerticalAlignment="Bottom" Opacity="0.5" Margin="20">
<TextBlock Text="-" FontSize="36" Height="60"></TextBlock>
</Button>
<Button Command="{Binding IncA}" Height="70" Width="70" VerticalAlignment="Bottom" Opacity="0.5" Margin="20">
<TextBlock Text="+" FontSize="36" Height="60"></TextBlock>
</Button>
</StackPanel>
</Grid>
</Border>
<Border Background="#FF7E0E03" Grid.Column="1">
<Grid>
<Viewbox>
<Label Content="{Binding ScoreB}" ContentStringFormat="D2" FontFamily="Lucida Console"></Label>
</Viewbox>
<StackPanel Orientation="Horizontal" HorizontalAlignment="Center">
<Button Command="{Binding DecB}" Height="70" Width="70" VerticalAlignment="Bottom" Opacity="0.5" Margin="20">
<TextBlock Text="-" FontSize="36" Height="60"></TextBlock>
</Button>
<Button Command="{Binding IncB}" Height="70" Width="70" VerticalAlignment="Bottom" Opacity="0.5" Margin="20">
<TextBlock Text="+" FontSize="36" Height="60"></TextBlock>
</Button>
</StackPanel>
</Grid>
</Border>
</Grid>
</DockPanel>
笔记
Score.ScoreX 变成 ScoreXText="{Binding Score.ScoreA, Mode=OneWay}" 变成 Text="{Binding ScoreA, UpdateSourceTrigger=PropertyChanged}"Interaction.Trigger