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wpf - 在 F# WPF MVVM 应用程序中绑定(bind)到 TextBox 的 TextChanged 事件

转载 作者:行者123 更新时间:2023-12-04 19:46:14 24 4
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我想绑定(bind)到使用 FsXaml 和 FSharp.ViewModule 构建的 MVVM F# 应用程序中的 WPF TextBox。我向描述的应用程序添加了一个名为“SetA”的命令 here ,并尝试使用以下 XAML 绑定(bind)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>

TextBox 是从 ScoreA 属性正确填充的,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 View 模型:

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。

最佳答案

很可能正在调用 Command,但结果不是您所期望的。

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。无论您如何更改分数,都会弹出一个消息框。

您还可以保留 EventValueCommand

member this.SetA = this.Factory.EventValueCommand(SetA)

并在 update 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

回到不是您所期望的 部分,我假设您希望记分牌中的分数在您更改 TextBox.Text 值时更新。

正如您所注意到的,没有(纯粹的)方法可以使用当前的 controllerTextBox.Text 值带入 update 中.由于 SetX 行为未修复,这与 IncX、DecX 或 New 事件不同。

选项:

  • 您可以将 Controller 的签名更改为 Score -> ScoringEvent -> string option -> Score 并使用选项值来处理 update 有趣。

  • 您可以处理 ViewModel 中的所有内容。记录的不可变特性强制使用 OneWay Binding。我会保持它不可变,但您可以(分解)组合 ViewModel 中的所有内容。

尝试

View 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>

注释

  • Score.ScoreX 更改为 ScoreX
  • Text="{Binding Score.ScoreA, Mode=OneWay}" 更改为 Text="{Binding ScoreA, UpdateSourceTrigger=PropertyChanged}"
  • 删除了 Interaction.Trigger

关于wpf - 在 F# WPF MVVM 应用程序中绑定(bind)到 TextBox 的 TextChanged 事件,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/41539544/

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