Questions on UI for Xamarin Forum

1 answer

274 views

I'm trying to create a custom expand / collapse indicator for my tree items but there is one situation where it is not working: when the item has no children the indicator is wrong. I'm using the technique suggested in this forum post to fill my tree on demand.

I have tried two different approaches but neither one gives an accurate result.

1. Binding to IsExpanded:

I have created a value converter:

public class TreeIconConverter : IValueConverter

{

public string ExpandIcon { get; set; }

public string CollapseIcon { get; set; }

public string LeafIcon { get; set; }

public object Convert(object value, Type targetType, object parameter, CultureInfo culture)

{

if (value is bool expanded)

return expanded ? CollapseIcon : ExpandIcon;

return null;

}

public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)

{

throw new NotImplementedException();

}

and I'm using a Label as the custom tree indicator:

<Label HeightRequest="24" WidthRequest="24" HorizontalOptions="Center" VerticalOptions="Center"

FontFamily="{StaticResource IconFont}" FontSize="{StaticResource SelectionIconSize}"

Text="{Binding IsExpanded, Converter={StaticResource TreeIconConverter}}"/>

This gives the best result, but when the item has no children the ExpandIcon is shown.

2. Binding to TreeViewDataItem:

I have altered the value converter to try and detect when the item has children:

public class TreeIconConverter : IValueConverter

{

public string ExpandIcon { get; set; }

public string CollapseIcon { get; set; }

public string LeafIcon { get; set; }

public object Convert(object value, Type targetType, object parameter, CultureInfo culture)

{

if (value is TreeViewDataItem item)

{

if (!item.IsExpanded)

return CollapseIcon;

if (item.Item is LocationGroup group)

{

if (group.HaveChildren && group.Children.Count == 0)

return LeafIcon;

}

return ExpandIcon;

}

return null;

}

public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)

{

throw new NotImplementedException();

}

group.HaveChildren is true only after getting the group's children, if it's false we don't yet have the group's children in memory.

The Label has been changed to:

<Label HeightRequest="24" WidthRequest="24" HorizontalOptions="Center" VerticalOptions="Center"

FontFamily="{StaticResource IconFont}" FontSize="{StaticResource SelectionIconSize}"

Text="{Binding ., Converter={StaticResource TreeIconConverter}}"/>

With this second version, all the items always show the CollapseIcon.

TreeView

answered on 26 Jun 2018

6 answers

329 views

Change font

How does one change the font family used by the calendar?

Calendar & Scheduling

answered on 25 Jun 2018

1 answer

109 views

Scroll to item

What would be the best way to make an item visible? Something similar to the ListView's ScrollItemIntoView method?

TreeView

answered on 22 Jun 2018

2 answers

125 views

On demand update

Does the TreeView support any kind of on demand update?

In other words: does it require the entire tree to be available on load, or can a node's children be made available only when expanding the node?

TreeView

answered on 22 Jun 2018

3 answers

63 views

Telerik Calendar crashes iOS preview

When I have a calendar in a page it works in the app, but the preview in Visual Studio Mac crashes. Is there a fix for this?

Calendar & Scheduling

answered on 20 Jun 2018

1 answer

141 views

Can't resolve the reference to method "SetupBlockUnsafe"

I have installed Xamarin UI and it give an error upon compilation...

/iOS/MTOUCH: Error MT2101: Can't resolve the reference 'System.Void ObjCRuntime.BlockLiteral::SetupBlockUnsafe(System.Delegate,System.Delegate)', referenced from the method 'System.Void TelerikUI.TKListView::PerformBatchUpdates(System.Action,System.Action`1<System.Boolean>)' in 'Xamarin.iOS, Version=0.0.0.0, Culture=neutral, PublicKeyToken=84e04ff9cfb79065'. (MT2101) (iOS)

How do I fix this?

General Discussions

answered on 16 Jun 2018

1 answer

232 views

Selection Persistance on Filtering

Hi,

I'm using XamarinForms and have a telerik listview and an entry on a page and am using the entry to filter the listview. I have the filter wired up to my ViewModel and it is working without issue. However, I now notice that the multiple section that is enabled does not persist after the filter is applied. And since the SelectedItems property cannot be bound in MVVM, I cannot easily re-apply those selected items. Is there a property/workaround that will allow that persistence?

ListView