Item Reordering in Xamarin ListView (SfListView)

The SfListView allows reordering by dragging and dropping items. It supports displaying the customized view in a template while dragging the item. It can be enabled by setting the SfListView.DragStartMode property to OnHold. The drag and drop options are listed as follows:

  • None: Disables drag and drop. This is the default value.
  • OnHold: Allows dragging and dropping by holding the item.
  • OnDragIndicator: Allows dragging and dropping by loading the DragIndicatorView within SfListView.ItemTemplate.

NOTE

The GridLayout does not support drag and drop.

The drag and drop scenarios are as follows:

  • Items can be reordered to any position by auto-scrolling.
  • Items can be reordered in same group or in other groups but, no groups can be added to other groups.
  • Groups, header, and footer cannot be reordered.

To enable drag and drop using ‘OnHold’, follow the code example:

<ContentPage  xmlns:syncfusion="clr-namespace:Syncfusion.ListView.XForms;assembly=Syncfusion.SfListView.XForms">
  <syncfusion:SfListView x:Name="listView" 
                   ItemsSource="{Binding ToDoList}"
                   DragStartMode="OnHold"
                   BackgroundColor="#FFE8E8EC"
                   ItemSize="60" />
</ContentPage>
listView.DragStartMode = DragStartMode.OnHold;

To enable drag and drop using both ‘OnHold’ and ‘OnDragIndicator’, follow the code example:

<ContentPage xmlns:syncfusion="clr-namespace:Syncfusion.ListView.XForms;assembly=Syncfusion.SfListView.XForms">
  <syncfusion:SfListView x:Name="listView" 
                   ItemsSource="{Binding ToDoList}"
                   DragStartMode="OnHold, OnDragIndicator"
                   BackgroundColor="#FFE8E8EC"
                   ItemSize="60" />
</ContentPage>
listView.DragStartMode = DragStartMode.OnHold | DragStartMode.OnDragIndicator;

NOTE

Reordering changes made only in view, and not in underlying collection. Thus, the changes will be reverted when performing sorting, grouping, or any other operation that refreshes view. You can update underlying collection by setting UpdateSource to true.

Drag indicator view

To drag and drop the items by DragIndicatorView, set the SfListView.DragStartMode property to OnDragIndicator. To display the dragging item, define any custom user interface(UI) in DragIndicatorView.

NOTE

You must set the SfListView instance as reference to the ListView property in DragIndicatorView.

<ContentPage xmlns:syncfusion="clr-namespace:Syncfusion.ListView.XForms;assembly=Syncfusion.SfListView.XForms">
  <syncfusion:SfListView x:Name="listView" 
                   ItemsSource="{Binding ToDoList}"
                   DragStartMode="OnDragIndicator"
                   BackgroundColor="#FFE8E8EC"
                   ItemSize="60">
  <syncfusion:SfListView.ItemTemplate>
    <DataTemplate>
      <Grid Padding="10">
          <Grid.ColumnDefinitions>
            <ColumnDefinition Width="*" />
            <ColumnDefinition Width="60" />
          </Grid.ColumnDefinitions>
          <Label x:Name="textLabel" Text="{Binding Name}" Grid.Column="1" FontSize="15" TextColor="#333333" />
          <syncfusion:DragIndicatorView Grid.Column="2" ListView="{x:Reference listView}" 
                    HorizontalOptions="Center" 
                    VerticalOptions="Center">
            <Grid Padding="10, 20, 20, 20">
              <Image Source="DragIndicator.png" />
            </Grid>
          </syncfusion:DragIndicatorView>
        </Grid>
      </Grid>
    </DataTemplate>
  </syncfusion:SfListView.ItemTemplate>
</syncfusion:SfListView>                
</ContentPage>
listView.ItemTemplate = new DataTemplate(() =>
{
  var grid = new Grid();
  var name = new Label
  {
    FontSize = 15,
    VerticalOptions = LayoutOptions.Center
  };
  name.SetBinding(Label.TextProperty, new Binding("Name"));

  var indicatorGrid = new Grid()
  {
    Padding = new Thickness(10, 20, 20, 20),
    HorizontalOptions = LayoutOptions.End,
    VerticalOptions = LayoutOptions.Center
  };
  var dragIndicatorView = new DragIndicatorView() { ListView = this.listView };
  var indicator = new Image() { Source = "DragIndicator.png" };

  indicatorGrid.Children.Add(indicator);
  dragIndicatorView.Content = indicatorGrid;

  grid.Children.Add(name);
  grid.Children.Add(dragIndicatorView, 1, 0);
  return grid;
});

The screenshot shows the output of the reordering items by drag and drop. Download the entire source code from GitHub here.

Item reordering by drag and drop

Drag item customization

By defining the SfListView.DragItemTemplate of the SfListView, displays the custom User Interface(UI) when performing drag and drop operations. The template can be defined either in code or XAML.

NOTE

If BackgroundColor is set to DragItemTemplate or DragIndicatorView, set InputTransparent to true. Since, dragging does not happen when performing by DragIndicatorView in UWP.

<ContentPage xmlns:syncfusion="clr-namespace:Syncfusion.ListView.XForms;assembly=Syncfusion.SfListView.XForms">
  <syncfusion:SfListView x:Name="listView" 
                   ItemsSource="{Binding ToDoList}"
                   DragStartMode="OnHold"
                   BackgroundColor="#FFE8E8EC"
                   ItemSize="60">
  <syncfusion:SfListView.DragItemTemplate>
    <DataTemplate>
      <Grid Padding="10">
        <Label x:Name="textLabel" Text="{Binding Name}" FontSize="15" />
      </Grid>
    </DataTemplate>
  </syncfusion:SfListView.DragItemTemplate>
</syncfusion:SfListView>                
</ContentPage>
listView.ItemTemplate = new DataTemplate(() => {
  var grid = new Grid();
  var name = new Label { FontSize = 15 };
  name.SetBinding(Label.TextProperty, new Binding("Name"));
  grid.Children.Add(name);
  return grid;
});

Event

The ItemDragging event is raised while dragging and dropping the item in the SfListView. The ItemDraggingEventArgs has the following members which provides the information for the ItemDragging event:

  • Action: Returns the drag Action such as start, dragging, and drop.
  • Bounds: Return bounds of drag item when dragging and dropping.
  • Handled: If this member is set to true, dragging can be handled. It is applicable only if Action is Dragging.
  • ItemData: Returns the underlying data of the dragging item.
  • NewIndex: Returns the item index of the DataSource.DisplayItems where dragging item is going to be dropped.
  • OldIndex: Returns the item index of the DataSource.DisplayItems where dragging item started. The OldIndex and NewIndex will be same if Action is Start.
  • Position: Returns the touch position of the drag item from screen coordinates.

Auto scroll options

Auto scroll margin

To adjust auto scroll margin, set a value to the ScrollMargin property of AutoScroller to enable auto-scrolling while dragging. The default value is 15. Auto-scrolling will be enabled when reaching ScrollMargin from view bounds while dragging.

To disable auto-scrolling, set the value to 0 for ScrollMargin.

this.listView.AutoScroller.ScrollMargin = 20;

Auto scroll interval

To adjust auto-scroll interval while dragging, set the Interval property of AutoScroller. The default value is 150 milliseconds.

this.listView.AutoScroller.Interval = new TimeSpan(0, 0, 0, 0, 200);

Disable outside scroll

To disable auto-scroll when dragging item moves outside the SfListView while dragging, set the AllowOutsideScroll property of AutoScroller to true. The default value is true.

this.listView.AutoScroller.AllowOutsideScroll = false;

Disable dragging for particular item

To disable dragging for a particular item, handle the ItemDragging event based on the conditions of Action event argument.

private void ListView_ItemDragging(object sender, ItemDraggingEventArgs e)
{
  // Disable the dragging for 4th item.
  if (e.Action == DragAction.Start && e.NewIndex == 3)
    e.Cancel = true;
}

Cancel dropping for the dragged item

To cancel dropping for the dragged item, handle the ItemDragging event based on the conditions of Action event argument.

using Syncfusion.ListView.XForms.Control.Helpers;
private void ListView_ItemDragging(object sender, ItemDraggingEventArgs e)
{
  // Cancel the dropping if drop the drag item into out of view.
  var listView = sender as ListView;
  var totalExtent = listView.GetVisualContainer().Bounds.Bottom;
  if (e.Action == DragAction.Drop && (e.Bounds.Y < -30 || e.Bounds.Bottom > totalExtent + 40))
    e.Cancel = true;
}

Reorder the underlying collection

The underlying collection can be reordered directly by setting the UpdateSource property to true. The default value is false.

this.listView.DragDropController.UpdateSource = true;

We can able to update collection even when UpdateSource is false. Like, user can decide where dragged item should be dropped actually by handling the ItemDragging event with DragAction.Drop.

private void ListView_ItemDragging(object sender, ItemDraggingEventArgs e)
{
   if (e.Action == DragAction.Drop)
      {
        ViewModel.ToDoList.MoveTo(1, 5);
      }
}

NOTE

Underlying collection will not be updated when any data operation like sorting or grouping is performed. The order will be maintained only in DisplayItems of data source. When drag and drop an item between groups, the value of the property in which grouping is performed is updated in data object.

Delete item when dropping in particular view

To delete the dragged item when dropping into a particular view, handle the ItemDragging event based on the conditions of Action and Bounds event arguments.

To delete the dragged item from the underlying collection when dropping into delete icon, follow the code example. It will enable or disable whenever drag started, and dropped by IsVisible property in ViewModel.

<ContentPage xmlns:syncfusion="clr-namespace:Syncfusion.ListView.XForms;assembly=Syncfusion.SfListView.XForms">
<Grid>
  <Grid.RowDefinitions>
    <RowDefinition Height="Auto" />
    <RowDefinition Height="*" />
  </Grid.RowDefinitions>

  <Grid BackgroundColor="#2196F3">
    <Label Text="To Do Items" x:Name="headerLabel"  TextColor="White" FontAttributes="Bold" VerticalOptions="Center" HorizontalOptions="Center" />
    <StackLayout x:Name="stackLayout" IsVisible="{Binding IsVisible}" Orientation="Horizontal" VerticalOptions="Center" HorizontalOptions="Center">
      <Image Source="Delete.png" HeightRequest="30" WidthRequest="30" />
      <Label x:Name="deleteLabel" Text="Delete Item" FontAttributes="Bold" TextColor="White" />
    </StackLayout>
  </Grid>
  <syncfusion:SfListView x:Name="listView" Grid.Row="1"
                   ItemsSource="{Binding ToDoList}"
                   DragStartMode="OnHold"
                   BackgroundColor="#FFE8E8EC"
                   ItemSize="60" />
</Grid>            
</ContentPage>
public partial class MainPage : ContentPage
{
  public MainPage()
  {
    InitializeComponent();
    var grid = new Grid();
    grid.RowDefinitions.Add(new RowDefinition { Height = new GridLength(40) });
    grid.RowDefinitions.Add(new RowDefinition { Height = new GridLength(1, GridUnitType.Star) });
    var grid1 = new Grid();
    var headerLabel = new Label()
    {
      Text = "To Do Items"
    };
    var stackLayout = new StackLayout();
    stackLayout.SetBinding(StackLayout.IsVisibleProperty, new Binding("IsVisible"));
    var image = new Image() { Source = "Delete.png" };
    var deleteLabel = new Label() { Text = "DeleteItem" };
    stackLayout.Children.Add(image);
    stackLayout.Children.Add(deleteLabel);
    grid1.Children.Add(headerLabel);
    grid1.Children.Add(stackLayout);
    var listView = new SfListView()
    {
      DragStartMode = DragStartMode.OnHold,
      ItemSize = 60,
      SelectionMode = SelectionMode.None,
      BackgroundColor = Color.FromHex("#FFE8E8EC")
    };
    listView.SetBinding(ListView.ItemsSourceProperty, new Binding("ToDoList"));
    grid.Children.Add(grid1);
    grid.Children.Add(listView, 0, 1);
  }
}
private async void ListView_ItemDragging(object sender, ItemDraggingEventArgs e)
{
  var viewModel = this.listView.BindingContext as ViewModel;

  if (e.Action == DragAction.Start)
  {
    viewModel.IsVisible = true;
    this.stackLayout.Opacity = 0.25;
  }

  if(e.Action == DragAction.Dragging)
  {
    var position = new Point(e.Position.X - this.listView.Bounds.X, e.Position.Y - this.listView.Bounds.Y);
    if (this.stackLayout.Bounds.Contains(position))
      this.deleteLabel.TextColor = Color.Red;
    else
      this.deleteLabel.TextColor = Color.White;
  }

  if(e.Action == DragAction.Drop)
  {
    var position = new Point(e.Position.X - this.listView.Bounds.X, e.Position.Y - this.listView.Bounds.Y);
    if (this.stackLayout.Bounds.Contains(position))
    {
      await Task.Delay(100);
      viewModel.ToDoList.Remove(e.ItemData as ToDoItem);
    }
    viewModel.IsVisible = false;
    this.deleteLabel.TextColor = Color.White;
    this.headerLabel.IsVisible = true;
  }
}

Download the sample from GitHub here.

Delete item while drop in listview

Skip dragging item into another group

To skip dragging from one group to another group, handle the ItemDragging event based on the conditions of Action and Bounds event arguments.

NOTE

While auto-scrolling, dragging item cannot be skipped.

Skip the dragging item by bounds of dragging item, and bounds of current and next group item.

using Syncfusion.ListView.XForms.Control.Helpers;
private async void ListView_ItemDragging(object sender, ItemDraggingEventArgs e)
{
  if (e.Action == DragAction.Dragging)
  {
    var currentGroup = this.GetGroup(e.ItemData);
    var container = this.ListView.GetVisualContainer();
    var groupIndex = this.ListView.DataSource.Groups.IndexOf(currentGroup);
    var nextGroup = (groupIndex + 1 < this.ListView.DataSource.Groups.Count) ? this.ListView.DataSource.Groups[groupIndex + 1] : null;
    ListViewItem groupItem = null;
    ListViewItem nextGroupItem = null;

    foreach (ListViewItem item in container.Children)
    {
      if (item.BindingContext == null || !item.Visibility)
        continue;

      if (item.BindingContext.Equals(currentGroup))
        groupItem = item;

      if (nextGroup != null && item.BindingContext.Equals(nextGroup))
        nextGroupItem = item;
      }

      if (groupItem != null && e.Bounds.Y <= groupItem.Y + groupItem.Height || nextGroupItem != null && (e.Bounds.Y + e.Bounds.Height >= nextGroupItem.Y))
        e.Handled = true;
  }
}

private GroupResult GetGroup(object itemData)
{
  GroupResult itemGroup = null;

  foreach (var item in this.listView.DataSource.DisplayItems)
  {
    if (item is GroupResult)
      itemGroup = item as GroupResult;

    if (item == itemData)
      break;
  }
  return itemGroup;
}

Download sample from GitHub here

Drag and drop customization

Adjust drag item axis

To adjust drag item coordinates (X and Y) while dragging, returns true from virtual method CanAdjustDragItemAxis of DragDropController. By default, Y coordinates can be adjusted if SfListView.Orientation is Vertical, and X coordinates can be adjusted if Orientation is Horizontal.

this.listView.DragDropController = new DragDropControllerExt(this.listView);

public class DragDropControllerExt : DragDropController
{
  public DragDropControllerExt(SfListView listView) : base(listView)
  {

  }

  protected override bool CanAdjustDragItemAxis()
  {
    return true;
  }
}

Layout item on dragging

In the SfListView, layout the ListViewItem with different animations, and time on dragging by virtual method OnLayoutItem.

this.listView.DragDropController = new DragDropControllerExt(this.listView);

public class DragDropControllerExt : DragDropController
{
  public DragDropControllerExt(SfListView listView) : base(listView)
  {

  }

  protected override Task<bool> OnLayoutItem(View element, Rectangle rect)
  {
    return element.LayoutTo(rect, 250, Easing.BounceIn);
  }
}