问题
I'm developping a WPF touch application. I have a scrollviewer containing buttons. I want to scroll the display when I touch-drag the buttons, and call the button's command when I tap. Here's some code to get started:
<Window x:Class="wpf_Button_Scroll.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:my="clr-namespace:wpf_Button_Scroll"
Title="MainWindow" Height="350" Width="200">
<Window.DataContext>
<my:MyViewModel />
</Window.DataContext>
<Grid>
<ScrollViewer>
<ListView ItemsSource="{Binding MyData}" HorizontalAlignment="Stretch">
<ListView.ItemTemplate>
<DataTemplate>
<Button Content="{Binding}"
Command="{Binding DataContext.MyCommand, RelativeSource={RelativeSource AncestorType=ItemsControl}}"
CommandParameter="{Binding}"
Margin="5 2" Width="150" Height="50"
FontSize="30" />
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
</ScrollViewer>
</Grid>
</Window>
And the view model:
namespace wpf_Button_Scroll
{
class MyViewModel
{
public MyViewModel()
{
MyCommand = new ICommandImplementation();
}
public string[] MyData
{
get
{
return new string[]{
"one", "two", "three", "four", "five", "six", "seven", "eight", "nine", "ten",
"eleven", "twelve", "thirteen", "fourteen", "fifteen", "sixteen", "seventeen", "eighteen", "nineteen", "twenty"
};
}
}
public ICommand MyCommand { get; private set; }
private class ICommandImplementation : ICommand
{
public bool CanExecute(object parameter) { return true; }
public event EventHandler CanExecuteChanged;
public void Execute(object parameter) { System.Windows.MessageBox.Show("Button clicked! " + (parameter ?? "").ToString()); }
}
}
}
Intended behavior:
when the user taps a button, a message box appears with the text "Button clicked!" ==> OK
when the user presses a button and moves his finger (without releasing), the buttons scroll up and down ==> NOK
How can I achieve scrolling in a ScrollViewer that contains buttons?
I'm developping on Visual Studio 2013 on Windows 7, and I'm targeting a Windows 7 desktop and a Windows 8 tablet with the same codebase. Framework 4.0. If it's really necessary, I can upgrade to 4.5.2 (we have many users, so it's not trivial to upgrade).
回答1:
Since there were Button(s) in the ListView for which we have to make the command get executed when intended. So that's the tricky part was. I did it in below way:
XAML:
<Window.DataContext>
<local:MyViewModel />
</Window.DataContext>
<Grid>
<ScrollViewer>
<ListView ItemsSource="{Binding MyData}" HorizontalAlignment="Stretch" Name="listview" ScrollViewer.PanningMode="VerticalOnly">
<ListView.ItemTemplate>
<DataTemplate>
<Button Content="{Binding}"
Command="{Binding DataContext.MyCommand, RelativeSource={RelativeSource AncestorType=ItemsControl}}"
CommandParameter="{Binding}"
Margin="5 2" Width="150" Height="50"
FontSize="30" />
</DataTemplate>
</ListView.ItemTemplate>
<ListView.Resources>
<Style TargetType="Button">
<EventSetter Event="PreviewMouseMove" Handler="PreviewMouseMove" />
<EventSetter Event="Drop" Handler="Drop" />
<Setter Property="AllowDrop" Value="True" />
</Style>
</ListView.Resources>
</ListView>
</ScrollViewer>
</Grid>
ViewModel:
class MyViewModel
{
public MyViewModel()
{
MyCommand = new ICommandImplementation();
}
public ObservableCollection<string> MyData
{
get
{
return new ObservableCollection<string>(new string[]{
"one", "two", "three", "four", "five", "six", "seven", "eight", "nine", "ten",
"eleven", "twelve", "thirteen", "fourteen", "fifteen", "sixteen", "seventeen", "eighteen", "nineteen", "twenty"
});
}
}
public ICommand MyCommand { get; private set; }
private class ICommandImplementation : ICommand
{
public bool CanExecute(object parameter) { return true; }
public event EventHandler CanExecuteChanged;
public void Execute(object parameter) { System.Windows.MessageBox.Show("Button clicked! " + (parameter ?? "").ToString()); }
}
}
Events:
private void Drop(object sender, DragEventArgs e)
{
var source = e.Data.GetData("Source") as string;
if (source != null)
{
int newIndex = listview.Items.IndexOf((sender as Button).Content);
var list = listview.ItemsSource as ObservableCollection<string>;
list.RemoveAt(list.IndexOf(source));
list.Insert(newIndex, source);
}
}
private void PreviewMouseMove(object sender, MouseEventArgs e)
{
if (e.LeftButton == MouseButtonState.Pressed)
{
Task.Factory.StartNew(new Action(() =>
{
Thread.Sleep(500);
App.Current.Dispatcher.BeginInvoke(new Action(() =>
{
if (e.LeftButton == MouseButtonState.Pressed)
{
var data = new DataObject();
data.SetData("Source", (sender as Button).Content);
DragDrop.DoDragDrop(sender as DependencyObject, data, DragDropEffects.Move);
e.Handled = true;
}
}), null);
}), CancellationToken.None);
}
}
In this link I've written how Drag & Drop works in respect of events and their data sharing.
And I'm still working on scrolling part.
回答2:
Well, this is so simple that I feel embarrassed that I didn't find it earlier. I had to set the PanningMode property on the ScrollViewer.
Like this:
<ScrollViewer PanningMode="VerticalOnly">
Final code:
<Window x:Class="wpf_Button_Scroll.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:my="clr-namespace:wpf_Button_Scroll"
Title="MainWindow" Height="350" Width="200">
<Window.DataContext>
<my:MyViewModel />
</Window.DataContext>
<Grid>
<ScrollViewer PanningMode="VerticalOnly">
<ListView ItemsSource="{Binding MyData}" HorizontalAlignment="Stretch">
<ListView.ItemTemplate>
<DataTemplate>
<Button Content="{Binding}"
Command="{Binding DataContext.MyCommand, RelativeSource={RelativeSource AncestorType=ItemsControl}}"
CommandParameter="{Binding}"
Margin="5 2" Width="150" Height="50"
FontSize="30" />
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
</ScrollViewer>
</Grid>
</Window>
The View Model doesn't change
来源：https://stackoverflow.com/questions/37008970/wpf-scrollviewer-tap-click-tap-and-hold-drag-scroll-how-to-achieve-this