隣接サイズ変更のレスポンシブ レイアウト

public partial class App : Application
{
    static public int ScreenWidth;
    static public int ScreenHeight;
    static public float ScreenDensity = 1;
    ...
}

public class MainActivity : FormsAppCompatActivity
{
    protected override void OnCreate(Bundle bundle)
    {
        App.ScreenDensity = Resources.DisplayMetrics.Density;
        App.ScreenWidth   = Resources.DisplayMetrics.WidthPixels;
        App.ScreenHeight  = Resources.DisplayMetrics.HeightPixels;
        ...
    }
}

public partial class AppDelegate : FormsApplicationDelegate
{
    public override bool FinishedLaunching(UIApplication app, NSDictionary options)
    {
        App.ScreenWidth  = (int)UIScreen.MainScreen.Bounds.Width;
        App.ScreenHeight = (int)UIScreen.MainScreen.Bounds.Height;
        ...
    }
}

<Grid x:Name="RootLayout" Margin="10"  >
    <Grid.RowDefinitions>
        <RowDefinition Height="Auto" />
        <RowDefinition Height="*" />
    </Grid.RowDefinitions>

    <Button x:Name="Button" Text="Change Grid Size"/>

    <Grid x:Name="ContentLayout" Grid.Row="1">
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="Auto" />
            <ColumnDefinition Width="*" />
        </Grid.ColumnDefinitions>

        <Grid x:Name="LeftGutter" Grid.Column="0"
               MinimumWidthRequest="0"
               MinimumHeightRequest="100"
               BackgroundColor="#FFCBCBCB" />

        <ig:XamDataGrid x:Name="DataGrid" Grid.Column="1"
                        AutoGenerateColumns="False">
            <ig:XamDataGrid.ItemsSource>
                <local:SampleSalesTeam />
            </ig:XamDataGrid.ItemsSource>
            <ig:XamDataGrid.Columns>
                <ig:TextColumn PropertyPath="FirstName" />
                <ig:TextColumn PropertyPath="Territory" />
                <ig:NumericColumn PropertyPath="Sales"  />
            </ig:XamDataGrid.Columns>
        </ig:XamDataGrid>
    </Grid>
</Grid>

static int ContentMaxWidth = (int)(App.ScreenWidth / App.ScreenDensity);
static int LeftGutterWidth25 = (int)(ContentMaxWidth * .25);
static int LeftGutterWidth50 = (int)(ContentMaxWidth * .50);
static int DataGridWidth1 = ContentMaxWidth - LeftGutterWidth25;
static int DataGridWidth2 = ContentMaxWidth - LeftGutterWidth50;

Button.Clicked += Button_Clicked;
...
private void Button_Clicked(object sender, EventArgs e)
{
    // Condition 1: if LeftGutter has its default width
    // then set its width to LeftGutterStop: 25% of screen width
    if (LeftGutter.Width <= 0)
    {
        LeftGutter.WidthRequest = LeftGutterWidth25;
    }
    // Condition 2: if LeftGutter's width is equal to LeftGutterWidth25
    // then set its width to LeftGutterWidth50: 50% of screen width
    else if (LeftGutter.Width == LeftGutterWidth25)
    {
        LeftGutter.WidthRequest = LeftGutterWidth50;
    }
    // Condition 3: if LeftGutter's width is equal to LeftGutterWidth50
    // then set its width to  default state of 0
    else if (LeftGutter.Width == LeftGutterWidth50)
    {
        LeftGutter.WidthRequest = 0;
    }
}

private ResponsivePhase CreatePhase(string columnName, string propertyName, object value)
{
    var setter = new ColumnPropertySetter()
    {
        ColumnName = columnName,
        PropertyName = propertyName,
        Value = value,
    };
    return new ResponsivePhase().AddColumnPropertySetter(setter);
}

var state1 = new ResponsiveState();
state1.MaximumWidth = ContentMaxWidth;
state1.MinimumWidth = DataGridWidth1 + 1;
state1.AddResponsivePhase(CreatePhase("Territory", "IsHidden", false));
state1.AddResponsivePhase(CreatePhase("Sales", "IsHidden", false));

var state2 = new ResponsiveState();
state2.MaximumWidth = DataGridWidth1;
state2.MinimumWidth = DataGridWidth2 + 1;
state2.AddResponsivePhase(CreatePhase("Territory", "IsHidden", false));
state2.AddResponsivePhase(CreatePhase("Sales", "IsHidden", true));

var state3 = new ResponsiveState();
state3.MaximumWidth = DataGridWidth2;
state3.MinimumWidth = 0;
state3.AddResponsivePhase(CreatePhase("Territory", "IsHidden", true));
state3.AddResponsivePhase(CreatePhase("Sales", "IsHidden", true));

DataGrid.ResponsiveStates.Add(state1);
DataGrid.ResponsiveStates.Add(state2);
DataGrid.ResponsiveStates.Add(state3);

<ig:XamDataGrid x:Name="DataGrid" ColumnHidingAnimationMode="FadeOut">
...
</ig:XamDataGrid>

DataGrid.ColumnHidingAnimationMode = ColumnHidingAnimationMode.FadeOut;