Expanding the size of ListView cell on tap - xamarin

Question

I'm trying to implement a solution to increase the size of a ListView Cell when tapped using Xamarin Forms (and custom renderers if required).
I'm still pretty new to C#, and the idea of data binding is still a little unclear to me, however, it seems like that is the way to go to solve this problem (perhaps something along the lines of binding the Height / HeightRequest properties of the cell?).
My attempts thus far have been unsuccessful.
If anyone could give me a push in the right direction it would be much appreciated.
Thank you!

Answer 1

ViewCell does not expose Height as a BindableProperty in Xamarin.Forms 1.4.2x
However if you create your own BindableProperty in your Model you can achieve changing the height still as shown below:-
Model:-
public class MenuItem2 : BindableObject
{
public static readonly BindableProperty TextProperty = BindableProperty.Create<MenuItem2, string>(p => p.Text, default(string));
public static readonly BindableProperty CellHeightProperty = BindableProperty.Create<MenuItem2, int>(p => p.CellHeight, default(int));
public string Text
{
get { return (string)GetValue(TextProperty); }
set { SetValue(TextProperty, value); }
}
public int CellHeight
{
get { return (int)GetValue(CellHeightProperty); }
set { SetValue(CellHeightProperty, value); }
}
}
XAML:-
<StackLayout>
<Button x:Name="cmdButton1" Text="Change Cell Heights" Clicked="cmdButton1_Clicked"/>
<ListView x:Name="lstItems" />
</StackLayout>
XAML Code-Behind:-
lstItems.HasUnevenRows = true;
lstItems.ItemTemplate = new DataTemplate(typeof(Classes.MenuCell2));
//
lstItems.ItemsSource = new List<MenuItem2>
{
new MenuItem2(),
new MenuItem2(),
new MenuItem2(),
new MenuItem2(),
};
If you don't set .HasUnevenRows you will not be able to change the cell height.
void cmdButton1_Clicked(object sender, EventArgs e)
{
Random objRandom = new Random();
//
var objItems = lstItems.ItemsSource;
//
foreach (MenuItem2 objMenuItem in objItems)
{
int intNewCellHeight = objRandom.Next(80, 160);
objMenuItem.CellHeight = intNewCellHeight;
objMenuItem.Text = "Cell Height = " + intNewCellHeight.ToString();
}
}
Custom ViewCell:-
public class MenuCell2 : ViewCell
{
public MenuCell2()
{
Label objLabel = new Label
{
YAlign = TextAlignment.Center,
TextColor = Color.Yellow,
};
objLabel.SetBinding(Label.TextProperty, new Binding("Text"));
StackLayout objLayout = new StackLayout
{
Padding = new Thickness(20, 0, 0, 0),
Orientation = StackOrientation.Horizontal,
HorizontalOptions = LayoutOptions.StartAndExpand,
Children = { objLabel }
};
Frame objFrame_Inner = new Frame
{
Padding = new Thickness(15, 15, 15, 15),
HeightRequest = 36,
OutlineColor = Color.Accent,
BackgroundColor = Color.Blue,
Content = objLayout,
};
Frame objFrame_Outer = new Frame
{
Padding = new Thickness(0, 0, 0, 10),
Content = objFrame_Inner
};
View = objFrame_Outer;
this.BindingContextChanged += MenuCell2_BindingContextChanged;
}
void MenuCell2_BindingContextChanged(object sender, EventArgs e)
{
MenuItem2 objMenuItem = (MenuItem2)this.BindingContext;
objMenuItem.PropertyChanged += objMenuItem_PropertyChanged;
}
void objMenuItem_PropertyChanged(object sender, System.ComponentModel.PropertyChangedEventArgs e)
{
switch (e.PropertyName)
{
case "CellHeight":
this.Height = (this.BindingContext as MenuItem2).CellHeight;
(this.View as Frame).ForceLayout();
break;
}
}
Remember to call ForceLayout on the root element of the ViewCell's View property, so it can redraw correctly.
This will give you a result something similar to the following (tested only on WindowsPhone at present):-
In order to do it on a ViewCell being tapped, on the XAML Page add:-
lstItems.ItemTapped += lstItems_ItemTapped;
and then change the model for the item to something like this:-
void lstItems_ItemTapped(object sender, ItemTappedEventArgs e)
{
(e.Item as MenuItem2).CellHeight = 200;
}

Answer 2

Xamarin now has an official example of doing this right within xaml and xaml code behind:
Overview:
https://developer.xamarin.com/samples/xamarin-forms/UserInterface/ListView/DynamicUnevenListCells/
Code:
https://github.com/xamarin/xamarin-forms-samples/tree/master/UserInterface/ListView/DynamicUnevenListCells