xamarin.forms - 单击时设置 HVScrollView 项目的背景颜色
问题描述
我已经在 Xamarin.Forms 中实现了 HVScrollView 自定义渲染器,如下所示,并试图设置在点击/单击时选择的项目的背景颜色,但无法弄清楚如何做到这一点。
我不知道是否需要向自定义渲染器添加一些内容以使其显示所选项目,或者是否应该在我的标记中设置它。
请帮忙
public class HVScrollGridView : Grid
{
private ICommand _innerSelectedCommand;
private readonly ScrollView _scrollView;
private readonly StackLayout _itemsStackLayout;
public event EventHandler SelectedItemChanged;
public StackOrientation ListOrientation { get; set; }
public double Spacing { get; set; }
public static readonly BindableProperty SelectedCommandProperty =
BindableProperty.Create("SelectedCommand", typeof(ICommand), typeof(HVScrollGridView), null);
public static readonly BindableProperty ItemsSourceProperty =
BindableProperty.Create("ItemsSource", typeof(IEnumerable), typeof(HVScrollGridView), default(IEnumerable<object>), BindingMode.TwoWay, propertyChanged: ItemsSourceChanged);
public static readonly BindableProperty SelectedItemProperty =
BindableProperty.Create("SelectedItem", typeof(object), typeof(HVScrollGridView), null, BindingMode.TwoWay, propertyChanged: OnSelectedItemChanged);
public static readonly BindableProperty ItemTemplateProperty =
BindableProperty.Create("ItemTemplate", typeof(DataTemplate), typeof(HVScrollGridView), default(DataTemplate));
public ICommand SelectedCommand
{
get { return (ICommand)GetValue(SelectedCommandProperty); }
set { SetValue(SelectedCommandProperty, value); }
}
public IEnumerable ItemsSource
{
get { return (IEnumerable)GetValue(ItemsSourceProperty); }
set { SetValue(ItemsSourceProperty, value); }
}
public object SelectedItem
{
get { return (object)GetValue(SelectedItemProperty); }
set { SetValue(SelectedItemProperty, value); }
}
public DataTemplate ItemTemplate
{
get { return (DataTemplate)GetValue(ItemTemplateProperty); }
set { SetValue(ItemTemplateProperty, value); }
}
private static void ItemsSourceChanged(BindableObject bindable, object oldValue, object newValue)
{
var itemsLayout = (HVScrollGridView)bindable;
itemsLayout.SetItems();
}
public HVScrollGridView()
{
_scrollView = new ScrollView();
_itemsStackLayout = new StackLayout
{
BackgroundColor = BackgroundColor,
Padding = Padding,
Spacing = Spacing,
HorizontalOptions = LayoutOptions.FillAndExpand
};
_scrollView.BackgroundColor = BackgroundColor;
_scrollView.Content = _itemsStackLayout;
Children.Add(_scrollView);
}
protected virtual void SetItems()
{
_itemsStackLayout.Children.Clear();
_itemsStackLayout.Spacing = Spacing;
_innerSelectedCommand = new Command<View>(view =>
{
SelectedItem = view.BindingContext;
SelectedItem = null; // Allowing item second time selection
});
_itemsStackLayout.Orientation = ListOrientation;
_scrollView.Orientation = ListOrientation == StackOrientation.Horizontal
? ScrollOrientation.Horizontal
: ScrollOrientation.Vertical;
if (ItemsSource == null)
{
return;
}
foreach (var item in ItemsSource)
{
_itemsStackLayout.Children.Add(GetItemView(item));
}
_itemsStackLayout.BackgroundColor = BackgroundColor;
SelectedItem = null;
}
protected virtual View GetItemView(object item)
{
var content = ItemTemplate.CreateContent();
var view = content as View;
if (view == null)
{
return null;
}
view.BindingContext = item;
var gesture = new TapGestureRecognizer
{
Command = _innerSelectedCommand,
CommandParameter = view
};
AddGesture(view, gesture);
return view;
}
private void AddGesture(View view, TapGestureRecognizer gesture)
{
view.GestureRecognizers.Add(gesture);
var layout = view as Layout<View>;
if (layout == null)
{
return;
}
foreach (var child in layout.Children)
{
AddGesture(child, gesture);
}
}
private static void OnSelectedItemChanged(BindableObject bindable, object oldValue, object newValue)
{
var itemsView = (HVScrollGridView)bindable;
if (newValue == oldValue && newValue != null)
{
return;
}
itemsView.SelectedItemChanged?.Invoke(itemsView, EventArgs.Empty);
if (itemsView.SelectedCommand?.CanExecute(newValue) ?? false)
{
itemsView.SelectedCommand?.Execute(newValue);
}
}
public static explicit operator ListView(HVScrollGridView v)
{
throw new NotImplementedException();
}
}
解决方案
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