如何在页面加载时处理UWP按下事件？

Question

I can start typing in my control after clicking within the Grid, but I would like to be able to start typing without having to click first. Is there something that I can put in the code behind to give the keyboard input focus on page load?

In my View I have:

     <Grid x:Name="PageGrid"
      KeyDown="{x:Bind ViewModel.OnKeyboardNumberInput, Mode=OneWay}"

In my ViewModel I have:

        public void OnKeyboardNumberInput(object sender, KeyRoutedEventArgs e)
    {

Answer 1

You can do it in the Loaded event of your Page , this event

Occurs when a FrameworkElement has been constructed and added to the object tree, and is ready for interaction.

And if you want to enable the keyboard input, your control should be editable.

When you navigate to a Page , it will automatically focus on the first control in this Page . But we can change this focus like this:

XAML:

<Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
    <TextBox x:Name="txt1" VerticalAlignment="Center" HorizontalAlignment="Center" Width="400" />
    <TextBox x:Name="txt2" VerticalAlignment="Bottom" HorizontalAlignment="Center" Width="400" />
</Grid>

code behind:

public MainPage()
{
    this.InitializeComponent();
    this.Loaded += Page_Loaded;
}

private void Page_Loaded(object sender, RoutedEventArgs e)
{
    txt2.Focus(FocusState.Keyboard);
}

Noticed that you may have used MVVM pattern for your project, you can do it like this:

XAML:

<Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}" Loaded="{x:Bind ViewModel.page_Loaded, Mode=OneWay}">
    <TextBox x:Name="txt1" VerticalAlignment="Center" HorizontalAlignment="Center" Width="400" />
    <TextBox x:Name="txt2" VerticalAlignment="Bottom" HorizontalAlignment="Center" Width="400" />
</Grid>

code behind in your ViewModel:

public void page_Loaded(object sender, RoutedEventArgs e)
{
    var grid = sender as Grid;
    var tb = (TextBox)grid.FindName("txt2");
    tb.Focus(FocusState.Keyboard);
}

Answer 2

If you want to type in a specific control, setting focus to that control is better than attempting to handle keyboard events. Assuming a simple window:

<Window
    x:Class="WpfApplication1.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Loaded="OnWindowLoaded"
    Title="MainWindow" Height="350" Width="525">
    <Grid>
        <TextBox x:Name="myTextBox" />
    </Grid>
</Window>

And in code-behind:

private void OnWindowLoaded(object sender, RoutedEventArgs e)
{
    myTextBox.Focus();
}