Ios 当isVisible设置为true时,Listview未更新
我正在尝试创建一个带有可单击行的Ios 当isVisible设置为true时,Listview未更新,ios,listview,xamarin,expandablelistview,xamarin.forms,Ios,Listview,Xamarin,Expandablelistview,Xamarin.forms,我正在尝试创建一个带有可单击行的列表视图。单击行时,它会将子stacklayout设置为visibility true。这在安卓系统中可以正常工作,但在ios系统中不行。也许我做得不对。我还是一个初学者,你知道如何解决这个问题或者其他更好的方法吗? 问题是它在ios上打开,因此可见性会改变,但它不会更新单元格的高度。例如,如果向上滚动直到看不到打开的单元格,然后向下滚动,则单元格会在屏幕外更新。您将看到它已更新高度 我尝试使用自定义渲染器,但不知道从哪里开始 这是我的xaml: <?xml
列表视图。单击行时,它会将子stacklayout设置为visibility true。这在安卓系统中可以正常工作,但在ios系统中不行。也许我做得不对。我还是一个初学者,你知道如何解决这个问题或者其他更好的方法吗?
问题是它在ios上打开,因此可见性会改变,但它不会更新单元格的高度。例如,如果向上滚动直到看不到打开的单元格,然后向下滚动,则单元格会在屏幕外更新。您将看到它已更新高度
我尝试使用自定义渲染器,但不知道从哪里开始
这是我的xaml:
<?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="Lisa.Excelsis.Mobile.AssessmentPage" xmlns:local="clr-namespace:Lisa.Excelsis.Mobile;assembly=Lisa.Excelsis.Mobile">
<StackLayout>
<local:SpecialListView x:Name="CategoryList"
ItemsSource = "{Binding Categories}"
HasUnevenRows="true"
RowHeight="-1"
GroupDisplayBinding="{Binding Name}"
IsGroupingEnabled="true">
<local:SpecialListView.ItemTemplate>
<DataTemplate>
<ViewCell x:Name="ObservationCell">
<ViewCell.View>
<StackLayout x:Name="ObservationContainer"
HorizontalOptions="FillAndExpand"
Orientation="Vertical"
VerticalOptions="StartAndExpand"
BackgroundColor="White">
<StackLayout x:Name="Observation"
HorizontalOptions="FillAndExpand"
VerticalOptions="StartAndExpand"
Padding="15, 10, 10, 10"
BackgroundColor="White">
<StackLayout.GestureRecognizers>
<TapGestureRecognizer Tapped="OpenItem"/>
</StackLayout.GestureRecognizers>
<Grid HorizontalOptions="FillAndExpand" >
<Grid.RowDefinitions>
<RowDefinition Height="Auto" />
<RowDefinition Height="Auto" />
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="35" />
<ColumnDefinition Width="*" />
</Grid.ColumnDefinitions>
<Label x:Name="ObservationOrder"
Text="{Binding Criterion.Order, StringFormat='{0}.'}"
FontSize="18"
VerticalOptions="StartAndExpand"
Grid.Column="0" Grid.Row="0"/>
<Label x:Name="ObservationTitle"
Text="{Binding Criterion.Title}"
FontSize="18"
VerticalOptions="StartAndExpand"
Grid.Column="1" Grid.Row="0"/>
</Grid>
</StackLayout>
<StackLayout x:Name="ObservationButtons"
HorizontalOptions="FillAndExpand"
VerticalOptions="StartAndExpand"
BackgroundColor="White"
IsVisible="false"
Padding="0, 0, 0, 20"
ClassId = "{Binding Id, StringFormat='ObservationButtons_{0}'}">
<Grid HorizontalOptions="Center"
Grid.Column="0" Grid.Row="1" Grid.ColumnSpan="2">
<Grid.RowDefinitions>
<RowDefinition Height="Auto" />
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="80" />
<ColumnDefinition Width="80" />
<ColumnDefinition Width="10" />
<ColumnDefinition Width="80" />
<ColumnDefinition Width="80" />
<ColumnDefinition Width="80" />
<ColumnDefinition Width="80" />
</Grid.ColumnDefinitions>
<StackLayout Grid.Column="0" Grid.Row="0" >
<Image Source="yesnobutton0.png"
HeightRequest="60" WidthRequest="60"
HorizontalOptions="Center"
VerticalOptions="Start"
x:Name="yesImage">
<Image.GestureRecognizers>
<TapGestureRecognizer Tapped="SetYesImage"/>
</Image.GestureRecognizers>
</Image>
<Label Text="Ja" VerticalOptions="End" HorizontalOptions="Center"/>
</StackLayout>
<StackLayout Grid.Column="1" Grid.Row="0">
<Image Source="yesnobutton0.png"
HeightRequest="60" WidthRequest="60"
HorizontalOptions="Center"
VerticalOptions="Start"
x:Name="noImage">
<Image.GestureRecognizers>
<TapGestureRecognizer Tapped="SetNoImage"/>
</Image.GestureRecognizers>
</Image>
<Label Text="Nee" VerticalOptions="End" HorizontalOptions="Center"/>
</StackLayout>
<Image Source="maybenot.png"
HeightRequest="60" WidthRequest="60"
HorizontalOptions="Center"
VerticalOptions="Start"
Grid.Column="3" Grid.Row="0">
<Image.GestureRecognizers>
<TapGestureRecognizer Tapped="SetMark"/>
</Image.GestureRecognizers>
</Image>
<Image Source="skip.png"
HeightRequest="60" WidthRequest="60"
HorizontalOptions="Center"
VerticalOptions="Start"
Grid.Column="4" Grid.Row="0">
<Image.GestureRecognizers>
<TapGestureRecognizer Tapped="SetMark"/>
</Image.GestureRecognizers>
</Image>
<Image Source="unclear.png"
HeightRequest="60" WidthRequest="60"
HorizontalOptions="Center"
VerticalOptions="Start"
Grid.Column="5" Grid.Row="0">
<Image.GestureRecognizers>
<TapGestureRecognizer Tapped="SetMark"/>
</Image.GestureRecognizers>
</Image>
<Image Source="change.png"
HeightRequest="60" WidthRequest="60"
HorizontalOptions="Center"
VerticalOptions="Start"
Grid.Column="6" Grid.Row="0">
<Image.GestureRecognizers>
<TapGestureRecognizer Tapped="SetMark"/>
</Image.GestureRecognizers>
</Image>
</Grid>
</StackLayout>
</StackLayout>
</ViewCell.View>
</ViewCell>
</DataTemplate>
</local:SpecialListView.ItemTemplate>
</local:SpecialListView>
</StackLayout>
这是一个例子,说明了它如何在android上工作,以及我希望它如何在ios上工作。
我在一个小测试项目中重现了您的问题。我更喜欢通过数据绑定进行布局更改,而不是代码隐藏
让我们从模板开始:
<?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="App6.Page1">
<ListView x:Name="CategoryList"
BackgroundColor="Gray"
ItemsSource="{Binding Categories}"
SelectedItem="{Binding SelectedItem}"
HasUnevenRows="true"
RowHeight="-1">
<ListView.ItemTemplate>
<DataTemplate>
<ViewCell x:Name="ObservationCell">
<ViewCell.View>
<StackLayout x:Name="Observation"
HorizontalOptions="FillAndExpand"
VerticalOptions="StartAndExpand"
Padding="15, 10, 10, 10"
BackgroundColor="White">
<Label x:Name="ObservationTitle"
Text="{Binding Title}"
FontSize="18"
TextColor="Black"
VerticalOptions="StartAndExpand"/>
<StackLayout Orientation="Horizontal" IsVisible="{Binding IsSelected}">
<Image BackgroundColor="Fuchsia" WidthRequest="40" HeightRequest="40"></Image>
<Image BackgroundColor="Green" WidthRequest="40" HeightRequest="40"></Image>
<Image BackgroundColor="Yellow" WidthRequest="40" HeightRequest="40"></Image>
<Image BackgroundColor="Blue" WidthRequest="40" HeightRequest="40"></Image>
<Image BackgroundColor="Black" WidthRequest="40" HeightRequest="40"></Image>
</StackLayout>
</StackLayout>
</ViewCell.View>
</ViewCell>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
</ContentPage>
视图模型
- 实现
INotifyPropertyChanged
以通知视图有关数据更改的信息
- 将一些虚拟项添加到我们的
类别集合中
- 具有更新类别的
IsSelected
属性的SelectedItem
属性
class Page1ViewModel:INotifyPropertyChanged
{
私有类别_selectedItem;
私有ObservableCollection_categories=新ObservableCollection();
公共事件属性更改事件处理程序属性更改;
公共可观测集合类别
{
获取{return\u categories;}
设置
{
_类别=价值;
OnPropertyChanged();
}
}
公共类别选择项
{
获取{return\u selectedItem;}
设置
{
如果(_selectedItem==值)
返回;
如果(_selectedItem!=null)
{
_selectedItem.IsSelected=false;
}
_选择editem=值;
如果(_selectedItem!=null)
{
_selectedItem.IsSelected=true;
}
}
}
[NotifyPropertyChangedInvocator]
受保护的虚拟void OnPropertyChanged([CallerMemberName]字符串propertyName=null)
{
PropertyChanged?.Invoke(这是新的PropertyChangedEventArgs(propertyName));
}
公共页面1ViewModel()
{
类别。添加(新类别());
类别。添加(新类别());
类别。添加(新类别());
类别。添加(新类别());
类别。添加(新类别());
}
}
最后,但并非最不重要,但最重要的是,您需要一个覆盖默认渲染器的小型自定义渲染器。如果SelectedItem
已更改,我们将调用ReloadData()
[assembly: ExportRenderer(typeof(ListView), typeof(MyListViewRenderer))]
namespace App6.iOS.CustomRenderer
{
public class MyListViewRenderer : ListViewRenderer
{
protected override void OnElementPropertyChanged(object sender, PropertyChangedEventArgs e)
{
base.OnElementPropertyChanged(sender, e);
if (e.PropertyName == ListView.SelectedItemProperty.PropertyName)
{
Device.BeginInvokeOnMainThread(() => Control.ReloadData());
}
}
}
}
结果
你试过给ForceL打电话吗
[assembly: ExportRenderer(typeof(ListView), typeof(MyListViewRenderer))]
namespace App6.iOS.CustomRenderer
{
public class MyListViewRenderer : ListViewRenderer
{
protected override void OnElementPropertyChanged(object sender, PropertyChangedEventArgs e)
{
base.OnElementPropertyChanged(sender, e);
if (e.PropertyName == ListView.SelectedItemProperty.PropertyName)
{
Device.BeginInvokeOnMainThread(() => Control.ReloadData());
}
}
}
}