Need this feature too

 Also vertical grid splitter.

This  content view can be used to resize the Grid window by dragging.

However, this method is only valid for the horizontal direction.

Here's a cleaner approach:

Add a Drop Gesture Recognizer to your Grid and subscribe to the DragOver event:

<Grid  x:Name="myGrid" Grid.Row="1">
<Grid.GestureRecognizers>
<DropGestureRecognizer DragOver="DropGestureRecognizer_DragOver">
</DropGestureRecognizer>
</Grid.GestureRecognizers>

Place the splitter in your grid between two columns:

xmlns:local="clr-namespace:yournamespace.Controls"

<local:SplitterControl Grid.Column="1" x:Name="splitter"/>

Call to SplitterControl Class

    private void DropGestureRecognizer_DragOver(object sender, DragEventArgs e)
    {
        splitter.UpdateSplitterPosition(sender, e);
    }

Add the SplitterControl class to your project:

namespace YourNameSpace.Resources.Controls;

public partial class SplitterControl : ContentView
{

public SplitterControl()
{
InitializeComponent();
}

private void OnDragStarting(object sender, DragStartingEventArgs e)
{
splitter.IsVisible = false;
}

public void UpdateSplitterPosition(object sender, DragEventArgs e)
{
int columnIndex = Grid.GetColumn(this);
columnIndex--;

var newWidth = (int)e.GetPosition(null)!.Value.X;

if (DeviceInfo.Platform == DevicePlatform.WinUI)
{
e.PlatformArgs.DragEventArgs.DragUIOverride!.IsCaptionVisible = false;
e.PlatformArgs.DragEventArgs.DragUIOverride!.IsGlyphVisible = false;
}

splitter.IsVisible = true;

var parentGrid = Parent as Grid;

if (parentGrid != null && columnIndex < parentGrid.ColumnDefinitions.Count)
{
parentGrid.ColumnDefinitions[columnIndex].Width = new GridLength(newWidth);
}
}
}

 

The recent .NET 8 update has now made it possible to create your own splitter.

Add DropGestureRecognizer to get cursor position:

    <Grid>
        <Grid.GestureRecognizers>
            <DropGestureRecognizer DragOver="DropGestureRecognizer_DragOver">
            </DropGestureRecognizer>
        </Grid.GestureRecognizers>

Create a BoxView to use as a splitter and place between two columns:

<!-- Splitter -->
<BoxView x:Name="splitter" 
Grid.Column="1" 
WidthRequest="5" 
BackgroundColor="Gray"                     
HorizontalOptions="Center" 
VerticalOptions="FillAndExpand" >
<BoxView.GestureRecognizers>
<DragGestureRecognizer DragStarting="DragGestureRecognizer_DragStarting" >                        
</DragGestureRecognizer>
</BoxView.GestureRecognizers>
</BoxView>

Hide splitter in DragStarting. This prevents a "double splitter" effect:

private void DragGestureRecognizer_DragStarting(object sender, DragStartingEventArgs e)
    {
        splitter.IsVisible = false;
    }

Calculate X position and set left column width. Make splitter Visible so we can see if while dragging. Use DragUIOverride options to hide caption and glyph while dragging.

    private void DropGestureRecognizer_DragOver(object sender, DragEventArgs e)
    {
        e.PlatformArgs.DragEventArgs.DragUIOverride!.IsCaptionVisible = false;
        e.PlatformArgs.DragEventArgs.DragUIOverride!.IsGlyphVisible = false;

        splitter.IsVisible = true;

        double newWidth = (int)e.GetPosition(null)!.Value.X;        
        myGrid.ColumnDefinitions[0].Width = new GridLength(newWidth);

    }

This would be an amazing feature and a bit surprised it is not there.

Feels like a fundamental part of a sophisticated UI to allow the user to apportion their available size as they see fit!!

Looking forward to it :)

looking for this feature too

I'm looking for this feature as well.