C# Xamarin渲染器不响应更改的属性
我对自定义渲染器有一些问题。我的示例基于Xamarin官方网站的示例,但我无法获取渲染器中的OnElementPropertyChanged方法,在向绑定列表添加项目时未触发该方法 单元格: 渲染器C# Xamarin渲染器不响应更改的属性,c#,mvvm,xamarin,xamarin.forms,C#,Mvvm,Xamarin,Xamarin.forms,我对自定义渲染器有一些问题。我的示例基于Xamarin官方网站的示例,但我无法获取渲染器中的OnElementPropertyChanged方法,在向绑定列表添加项目时未触发该方法 单元格: 渲染器 [assembly: ExportRenderer(typeof(MyNativeListView), typeof(Blabla.iOS.NativeiOSListViewRenderer))] namespace Blabla.iOS { public class NativeiOSLi
[assembly: ExportRenderer(typeof(MyNativeListView), typeof(Blabla.iOS.NativeiOSListViewRenderer))]
namespace Blabla.iOS
{
public class NativeiOSListViewRenderer : ListViewRenderer
{
protected override void OnElementChanged(ElementChangedEventArgs<Xamarin.Forms.ListView> e)
{
base.OnElementChanged(e);
if (e.OldElement != null)
{
// Unsubscribe
}
if (e.NewElement != null)
{
Control.Source = new NativeiOSListViewSource(e.NewElement as MyNativeListView);
}
}
protected override void OnElementPropertyChanged(object sender, System.ComponentModel.PropertyChangedEventArgs e)
{
base.OnElementPropertyChanged(sender, e);
if (e.PropertyName == MyNativeListView.ItemsProperty.PropertyName) //Only triggered for stuff like Height, Width and not Items
{
Control.Source = new NativeiOSListViewSource(Element as MyNativeListView);
}
}
}
}
视图模型
public class PlayGroundViewModel : INotifyPropertyChanged
{
public ICommand Add { get; private set; }
private ObservableCollection<ListItem> _localItems;
public ObservableCollection<ListItem> LocalItems { get { return _localItems; } set { _localItems = value; SetChangedProperty("LocalItems"); } }
public PlayGroundViewModel()
{
Add = new Command(() => { AddItem(); });
LocalItems = new ObservableCollection<ListItem>();
}
private void AddItem()
{
ListItem item = new ListItem("a", "b", true); //Just to get something to pop up in the list.
LocalItems.Add(item);
SetChangedProperty("LocalItems");
}
public event PropertyChangedEventHandler PropertyChanged;
private void SetChangedProperty(string property)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(property));
}
}
}
我已经验证了SetChangedProperty已被触发,但此后似乎什么也没有发生。如果有人知道原因,我将不胜感激。当属性确实发生更改时,会触发
PropertyChanged
事件。列表不会更改,只会更改其内容,因此列表本身的属性仍然引用同一对象(列表)
您正在使用一个可观察的集合
,这是一个好方法。问题是您必须在渲染器中订阅CollectionChanged
事件
此外,使用默认的
列表视图
并为单元格创建自定义呈现程序可能更容易。当属性确实发生更改时,会触发属性更改
事件。列表不会更改,只会更改其内容,因此列表本身的属性仍然引用同一对象(列表)
您正在使用一个可观察的集合
,这是一个好方法。问题是您必须在渲染器中订阅CollectionChanged
事件
此外,使用默认的ListView
并为单元格创建自定义渲染器可能更容易
<?xml version="1.0" encoding="UTF-8"?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms" xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" x:Class="Blabla.PlayGroundPage" xmlns:local="clr-namespace:Blabla;assembly=Blabla">
<ContentPage.Resources>
<ResourceDictionary>
<local:Inverter x:Key="inverter" />
</ResourceDictionary>
</ContentPage.Resources>
<ContentPage.Content>
<StackLayout>
<local:MyNativeListView x:Name="nativeListView" VerticalOptions="FillAndExpand" Items="{Binding LocalItems}" />
<Button Text="add" Command="{Binding Add}" />
</StackLayout>
</ContentPage.Content>
</ContentPage>
public partial class PlayGroundPage : ContentPage
{
public PlayGroundPage()
{
InitializeComponent();
PlayGroundViewModel viewModel = new PlayGroundViewModel();
BindingContext = viewModel;
}
}
public class PlayGroundViewModel : INotifyPropertyChanged
{
public ICommand Add { get; private set; }
private ObservableCollection<ListItem> _localItems;
public ObservableCollection<ListItem> LocalItems { get { return _localItems; } set { _localItems = value; SetChangedProperty("LocalItems"); } }
public PlayGroundViewModel()
{
Add = new Command(() => { AddItem(); });
LocalItems = new ObservableCollection<ListItem>();
}
private void AddItem()
{
ListItem item = new ListItem("a", "b", true); //Just to get something to pop up in the list.
LocalItems.Add(item);
SetChangedProperty("LocalItems");
}
public event PropertyChangedEventHandler PropertyChanged;
private void SetChangedProperty(string property)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(property));
}
}
}
public class ListItem
{
public string SelectedType { get; set; }
public string SelectedOption { get; set; }
public bool IsChecked { get; set; }
public ListItem(string selectedType, string selectedOption, bool isChecked)
{
SelectedType = selectedType;
SelectedOption = selectedOption;
IsChecked = isChecked;
}
}