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Fix IsNullOrEmptyStateTrigger on SelectedItem #4426

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Fix IsNullOrEmptyStateTrigger on SelectedItem #4426

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7b6794b
Init commit
XAML-Knight Dec 7, 2021
fac2b1b
Change default value from true to null
XAML-Knight Dec 10, 2021
0a7677c
Bring in another control for trigger
XAML-Knight Dec 13, 2021
31f1cc4
unit test not ready for show
XAML-Knight Dec 13, 2021
dae06ea
Light up IsActive DP
XAML-Knight Dec 14, 2021
50a0402
Finishing touches
XAML-Knight Dec 14, 2021
ccb6366
call SetActive in ctor
XAML-Knight Dec 21, 2021
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29 changes: 27 additions & 2 deletions Microsoft.Toolkit.Uwp.SampleApp/SamplePages/Triggers/IsNullOrEmptyStateTrigger.bind
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Original file line number Diff line number Diff line change
Expand Up @@ -33,6 +33,18 @@
</VisualState.Setters>
</VisualState>
</VisualStateGroup>
<VisualStateGroup x:Name="ListViewStates">
<VisualState x:Name="SelectedItemNotNullState" />
<VisualState x:Name="SelectedItemNullState">
<VisualState.StateTriggers>
<triggers:IsNullOrEmptyStateTrigger Value="{Binding SelectedItem, ElementName=SelectList}"/>
</VisualState.StateTriggers>
<VisualState.Setters>
<Setter Target="RemoveSelection.IsEnabled" Value="False" />
<Setter Target="SelectionEmptyMessage.Visibility" Value="Visible" />
</VisualState.Setters>
</VisualState>
</VisualStateGroup>
</VisualStateManager.VisualStateGroups>

<StackPanel HorizontalAlignment="Center" VerticalAlignment="Center">
Expand All @@ -43,7 +55,7 @@
<TextBlock x:Name="OurTextBoxError" Text="* Required" Foreground="Red" Margin="10 0 0 0" Visibility="Collapsed" VerticalAlignment="Center" />
</StackPanel>

<StackPanel Orientation="Horizontal">
<StackPanel Orientation="Horizontal" Margin="0,40,0,0">
<Button x:Name="AddButton" Content="Add" Margin="0 0 10 0"/>
<Button x:Name="RemoveButton" Content="Remove"/>
</StackPanel>
Expand All @@ -63,7 +75,20 @@
</Style>
</ListBox.ItemContainerStyle>
</ListBox>
<Border BorderBrush="Gold" BorderThickness="1" Margin="0,80,0,0" Width="275">
<StackPanel>
<Button x:Name="RemoveSelection" Content="Deselect" />
<TextBlock x:Name="SelectionEmptyMessage" Text="SelectedItem is empty, select an item" Visibility="Collapsed"
Margin="5,0,0,0"/>
<ListView x:Name="SelectList" HorizontalAlignment="Left">
<ListView.Items>
<TextBlock Text="One" />
<TextBlock Text="Two" />
<TextBlock Text="Three" />
</ListView.Items>
</ListView>
</StackPanel>
</Border>
</StackPanel>

</Grid>
</Page>
21 changes: 20 additions & 1 deletion Microsoft.Toolkit.Uwp.SampleApp/SamplePages/Triggers/IsNullOrEmptyStateTriggerPage.xaml.cs
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Expand Up @@ -16,6 +16,8 @@ public sealed partial class IsNullOrEmptyStateTriggerPage : Page, IXamlRenderLis
private Button _addButton;
private Button _removeButton;
private ListBox _listBox;
private Button _unselectButton;
private ListView _selectListView;

/// <summary>
/// Initializes a new instance of the <see cref="IsNullOrEmptyStateTriggerPage"/> class.
Expand Down Expand Up @@ -52,6 +54,15 @@ public void OnXamlRendered(FrameworkElement control)
}

_listBox = control.FindDescendant("OurList") as ListBox;

_selectListView = control.FindDescendant("SelectList") as ListView;

if (control.FindDescendant("RemoveSelection") is Button btn3)
{
_unselectButton = btn3;

_unselectButton.Click += this.UnselectButton_Click;
}
}

private void AddButton_Click(object sender, RoutedEventArgs e)
Expand All @@ -64,10 +75,18 @@ private void AddButton_Click(object sender, RoutedEventArgs e)

private void RemoveButton_Click(object sender, RoutedEventArgs e)
{
if (_listBox != null)
if (_listBox != null && _listBox.Items.Count > 0)
{
_listBox.Items.RemoveAt(0);
}
}

private void UnselectButton_Click(object sender, RoutedEventArgs e)
{
if(_selectListView != null && _selectListView.SelectedItem != null)
{
_selectListView.SelectedItem = null;
}
}
}
}
14 changes: 10 additions & 4 deletions Microsoft.Toolkit.Uwp.UI/Triggers/IsNullOrEmptyStateTrigger.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -28,22 +28,28 @@ public object Value
/// Identifies the <see cref="Value"/> DependencyProperty
/// </summary>
public static readonly DependencyProperty ValueProperty =
DependencyProperty.Register(nameof(Value), typeof(object), typeof(IsNullOrEmptyStateTrigger), new PropertyMetadata(true, OnValuePropertyChanged));
DependencyProperty.Register(nameof(Value), typeof(object), typeof(IsNullOrEmptyStateTrigger), new PropertyMetadata(null, OnValuePropertyChanged));
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/// <summary>
/// Initializes a new instance of the <see cref="IsNullOrEmptyStateTrigger"/> class.
/// </summary>
public IsNullOrEmptyStateTrigger()
{
SetActive(true);
}

private static void OnValuePropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
var obj = (IsNullOrEmptyStateTrigger)d;
var val = e.NewValue;

obj.SetActive(IsNullOrEmpty(val));

if (val == null)
{
return;
}

// Try to listen for various notification events
// Starting with INorifyCollectionChanged
// Starting with INotifyCollectionChanged
var valNotifyCollection = val as INotifyCollectionChanged;
if (valNotifyCollection != null)
{
Expand Down