那些遇到过的问题

当isVisible设置为true时,Listview未更新

Jim*_*Jim 7 listview expandablelistview ios xamarin xamarin.forms

我正在尝试ListView使用可点击的行.当您单击某一行时,它会将子堆栈布局设置为可见性为true.这在android中运行良好,但在ios中不行.也许我做错了.我仍然是初学者,任何想法如何解决这个或任何其他更好的方法？问题是它在ios上打开,因此可见性会发生变化,但它不会更新单元格的高度.例如,如果向上滚动直到无法再看到打开的单元格,然后向下滚动,则单元格会在屏幕外更新.你会看到它已经更新了高度.

我尝试使用自定义渲染器,但我不知道从哪里开始.

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>
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这是一个如何在Android上工作的例子以及我希望它如何在ios上工作. Listview示例

Sve*_*übe 5

我在一个小的Testproject中重现了你的问题.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>
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Datatemplate基本相同,但是:

  • 在StackLayout没有点击,监听器
  • StackLayout的可见性绑定到IsSelected(IsVisible="{Binding IsSelected}")
  • 该SelectedItem的ListView必然SelectedItem我们的视图模型

我们的页面只是设置ViewModel为DataContext

public partial class Page1 : ContentPage
{
    public Page1()
    {
        InitializeComponent();
        BindingContext = new Page1ViewModel();
    }
}
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该视图模型

  • 实现INotifyPropertyChanged通知视图有关数据更改
  • 在我们的CategoriesCollection中添加了一些虚拟物品
  • 有一个SelectedItem更新IsSelected类别属性的属性
class Page1ViewModel : INotifyPropertyChanged
{
    private Category _selectedItem;
    private ObservableCollection<Category> _categories = new ObservableCollection<Category>();
    public event PropertyChangedEventHandler PropertyChanged;

    public ObservableCollection<Category> Categories
    {
        get { return _categories; }
        set
        {
            _categories = value;
            OnPropertyChanged();
        }
    }

    public Category SelectedItem
    {
        get { return _selectedItem; }
        set
        {
            if (_selectedItem == value)
                return;

            if (_selectedItem != null)
            {
                _selectedItem.IsSelected = false;
            }

            _selectedItem = value;
            if (_selectedItem != null)
            {
                _selectedItem.IsSelected = true;
            }
        }
    }

    [NotifyPropertyChangedInvocator]
    protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }

    public Page1ViewModel()
    {
        Categories.Add(new Category());
        Categories.Add(new Category());
        Categories.Add(new Category());
        Categories.Add(new Category());
        Categories.Add(new Category());
    }
}
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最后但并非最不重要,但最重要的是,您需要一个小的自定义渲染器来覆盖默认渲染器.ReloadData()如果SelectedItem改变了,我们会打电话.

[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());
            }
        }
    }
}
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结果

列表视图与动态单元格

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