Use the DispatcherTimer, Popup and even a movie to enhance your data presentation

Article
11/21/2007

We can subclass the prior Windows Presentation Foundation (WPF) class called Browse that displays the results of a query. This subclass will add a WPF Popup to it.

The popup can easily be added to either a ListView or the ListBox sample I posted earlier (Use LINQ with WPF : Styles and DataTemplates in code)

The code sample below is exactly the same code as the prior Browse post except that it uses a subclass of the Browse class called BrowseWithPopup.

This class has a DispatcherTimer Class (System.Windows.Threading) that delays the opening of the descriptive popup. The timer starts when an item is selected. If it's been selected for, say 200 ms, then the popup displays. Thus, if the user is actively scrolling, no popup shows.

The System.Timers.Timer class runs in a different thread from the UI thread. WPF runs UI and rendering in different threads. See WPF Threading Model.

To add a movie to any UI element is quite simple. To make it repeat after playing once, you need to use the StoryBoard class to animate it. Try making it repeat forever!

Imports System.Windows.Controls.Primitives ' for Popup

Partial Public Class Window1

Private Sub Window1_Loaded(ByVal sender As System.Object, ByVal e As System.Windows.RoutedEventArgs) Handles MyBase.Loaded

Me.Width = 800

Me.Height = 800

Dim Query = From proc In System.Diagnostics.Process.GetProcesses _

Select proc.Id, proc.ProcessName, ThreadCount = proc.Threads.Count, proc.MainWindowTitle

'Me.Content = New Browse(Query, Me) ' the Browse will fill the entire window

Me.Content = New BrowseWithPopup(Query, Me)

End Sub

End Class

Class Browse

Inherits ListView

Sub New(ByVal Query As Object, Optional ByVal Parent As Object = Nothing)

Dim gv As New GridView

Me.View = gv

Me.ItemsSource = Query

If Not Parent Is Nothing Then

If Parent.GetType.BaseType Is GetType(Window) Then

CType(Parent, Window).Title = "# items = " + Me.Items.Count.ToString

End If

Me.AddHandler(GridViewColumnHeader.ClickEvent, New RoutedEventHandler(AddressOf HandleHeaderClick))

For Each mem In From mbr In _

Query.GetType().GetInterface(GetType(IEnumerable(Of )).FullName) _

.GetGenericArguments()(0).GetMembers _

Where mbr.MemberType = Reflection.MemberTypes.Property

Dim coltype = CType(mem, Reflection.PropertyInfo).PropertyType.Name

Select Case coltype

Case "Int32", "String"

Dim gvc As New GridViewColumn

gvc.Header = mem.Name

gv.Columns.Add(gvc)

If coltype = "Int32" Then

gvc.Width = 80

Dim dt As New DataTemplate

Dim factSP = New FrameworkElementFactory(GetType(StackPanel))

dt.VisualTree = factSP

factSP.SetValue(StackPanel.OrientationProperty, Orientation.Horizontal)

Dim factTb = New FrameworkElementFactory(GetType(TextBlock))

factTb.SetBinding(TextBlock.TextProperty, New Binding(mem.Name))

factTb.SetValue(TextBlock.FontWeightProperty, FontWeights.Bold)

' factTb.SetValue(TextBlock.BackgroundProperty, Brushes.SpringGreen)

factSP.AppendChild(factTb)

'factTb = New FrameworkElementFactory(GetType(Button))

'factTb.SetValue(Button.ContentProperty, "hit me")

'factSP.AppendChild(factTb)

gvc.CellTemplate = dt

Else

gvc.DisplayMemberBinding = New Binding(mem.Name)

gvc.Width = 180

End If

End Select

Dim MyListboxStyle As New Style(GetType(ListBoxItem))

Dim tr = New Trigger

tr.Property = ListBoxItem.IsSelectedProperty ' when Selected

tr.Value = True ' is true

tr.Setters.Add(New Setter(ListBoxItem.ForegroundProperty, Brushes.Bisque))

MyListboxStyle.Triggers.Add(tr)

tr = New Trigger

tr.Property = ListBoxItem.IsMouseOverProperty ' when mouseover

tr.Value = True ' is true

tr.Setters.Add(New Setter(ListBoxItem.ForegroundProperty, Brushes.Red))

tr.Setters.Add(New Setter(ListBoxItem.BackgroundProperty, Brushes.Aquamarine)) ' this trigger sets both fore and back properties

MyListboxStyle.Setters.Add(New Setter(ListBoxItem.ForegroundProperty, Brushes.RoyalBlue)) ' set style for all items

MyListboxStyle.Triggers.Add(tr)

Me.ItemContainerStyle = MyListboxStyle

End Sub

Dim _Lastdir As System.ComponentModel.ListSortDirection = ComponentModel.ListSortDirection.Ascending

Dim _LastHeaderClicked As GridViewColumnHeader = Nothing

Sub HandleHeaderClick(ByVal sender As Object, ByVal e As RoutedEventArgs)

If e.OriginalSource.GetType Is GetType(GridViewColumnHeader) Then

Dim gvh = CType(e.OriginalSource, GridViewColumnHeader)

Dim dir As System.ComponentModel.ListSortDirection = ComponentModel.ListSortDirection.Ascending

If Not gvh Is Nothing AndAlso Not gvh.Column Is Nothing Then

Dim hdr = gvh.Column.Header

If gvh Is _LastHeaderClicked Then

If _Lastdir = ComponentModel.ListSortDirection.Ascending Then

dir = ComponentModel.ListSortDirection.Descending

End If

Sort(hdr, dir)

_LastHeaderClicked = gvh

_Lastdir = dir

End If

End Sub

Sub Sort(ByVal sortby As String, ByVal dir As System.ComponentModel.ListSortDirection)

Me.Items.SortDescriptions.Clear()

Dim sd = New System.ComponentModel.SortDescription(sortby, dir)

Me.Items.SortDescriptions.Add(sd)

Me.Items.Refresh()

End Sub

End Class

Class BrowseWithPopup

Inherits Browse

Sub New(ByVal Query As Object, Optional ByVal Parent As Object = Nothing)

MyBase.new(Query)

Dim sp As New StackPanel

_lvPopUp.Child = sp

_tbListViewItemDescription.Foreground = Brushes.Black

_tbListViewItemDescription.Background = Brushes.LightYellow

sp.Children.Add(_tbListViewItemDescription)

'Return ' the rest of this method is fluff

Dim btnTest As New Button ' just for fun, let's add a button to the popup tip.

btnTest.Content = "foo"

btnTest.AddHandler(Button.ClickEvent, New RoutedEventHandler(AddressOf HandleClick))

sp.Children.Add(btnTest)

Dim MyVid As New MediaElement ' For more fun, let's add a movie to the popup tip

MyVid.MaxHeight = 100

MyVid.MaxWidth = 100

MyVid.Source = New Uri("d:\tshort.avi") ' change to point to your movie file

sp.Children.Add(MyVid)

End Sub

Sub HandleClick()

MsgBox("You Clicked me!")

End Sub

Dim _lvPopUp As New Popup

Dim WithEvents _lvTimer As New System.Windows.Threading.DispatcherTimer

Dim _tbListViewItemDescription As New TextBlock

Sub HandlePopupTimerTick() Handles _lvTimer.Tick

Dim lbi As ListBoxItem = Me.ItemContainerGenerator.ContainerFromIndex(Me.SelectedIndex)

If Not lbi Is Nothing Then

_lvPopUp.PlacementTarget = lbi

_tbListViewItemDescription.Text = "This is the data: " + vbCrLf + lbi.Content.ToString

_lvPopUp.IsOpen = 1

End If

End Sub

Sub HandleRowSelected(ByVal sender As Object, ByVal e As RoutedEventArgs) Handles Me.SelectionChanged

Dim lb = CType(sender, ListBox)

If Not lb Is Nothing AndAlso (lb.SelectedIndex >= 0) Then

Dim lbi As ListBoxItem = lb.ItemContainerGenerator.ContainerFromIndex(lb.SelectedIndex)

Dim lbi2 = lb.SelectedItem

If _lvPopUp.IsOpen Then

_lvPopUp.IsOpen = False

End If

_lvTimer.Stop() ' stop prior timer, if any

_lvTimer.Interval = TimeSpan.FromMilliseconds(500)

_lvTimer.Start()

_lvPopUp.AllowsTransparency = True

_lvPopUp.PopupAnimation = PopupAnimation.Fade

_lvPopUp.Placement = PlacementMode.Right

End If

End Sub

End Class

</Code Sample>

Comments

Anonymous
November 28, 2007
Using WPF, it’s great to use declarative XAML , but it’s also great to use dynamic code. With VB’s new
Anonymous
November 28, 2007
Using WPF, it’s great to use declarative XAML , but it’s also great to use dynamic code. With VB’s new
Anonymous
May 31, 2009
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Anonymous
June 08, 2009
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