Question

我正在使用堆栈视图中的可绑定布局来创建类别的水平列表，如下图所示，因此当我单击某个类别时，我想更改文本颜色，但是在实际绑定中不会更新视图在财产变更后被解雇。

                <StackLayout x:Name="CategoryStack" BindableLayout.ItemsSource="{Binding CategoryListItems,Mode=TwoWay}"
         Orientation="Horizontal" Padding="5,3,0,3" BackgroundColor="Transparent">
                    <BindableLayout.ItemTemplate>
                        <DataTemplate >
                            <custom:PancakeView BackgroundColor="White"  Grid.Row="0" Grid.Column="0" IsClippedToBounds="true" Padding="4" HeightRequest="47"  CornerRadius="5">
                                <Grid>
                                    <Label HorizontalTextAlignment="Center" Margin="0" VerticalOptions="Center" FontSize="Small"  Text="{Binding Name}" TextColor="{Binding NameColor,Mode=TwoWay}">

                                    </Label>
                                </Grid>


                                <custom:PancakeView.GestureRecognizers>
                                    <TapGestureRecognizer  CommandParameter="{Binding .}" Command="{Binding Path=BindingContext.CategoryTappedCmd,Source={x:Reference CategoryStack}}"  NumberOfTapsRequired="1" />
                                </custom:PancakeView.GestureRecognizers>

                            </custom:PancakeView>



                        </DataTemplate>
                    </BindableLayout.ItemTemplate>
                </StackLayout>

下面是我的ViewModel代码

  public class ProductsListViewModel : ViewModelBase
    {

    private ObservableCollection<SpicesCategory> _CategoryListItems = new ObservableCollection<SpicesCategory>();

    public ObservableCollection<SpicesCategory> CategoryListItems
    {
        get => _CategoryListItems;
        set
        {
            _CategoryListItems = value;
            RaisePropertyChanged(() => (CategoryListItems));
        }
    }

  public ICommand CategoryTappedCmd => new Command(CategoryTapped);

    public async void CategoryTapped(object obj)
    {


        SpicesCategory SelectedspicesCategory = obj as SpicesCategory;

        foreach (var item in CategoryListItems)
        {
            if(item == SelectedspicesCategory)
            {
                item.IsSelected = true;

                item.NameColor = Color.Red;
            }
            else
            {
                item.IsSelected = false;
                item.NameColor = Color.Black;
            }

        }

    }
 }

和下面是我的SpicesCategory模型

public  class SpicesCategory
{
    public long Id { get; set; }
    public string Name { get; set; }

    public bool IsSelected { get; set; }

    public Color NameColor { get; set; }
}

下面是我的ViewModelBase继承ExtendedBindableObject

 public class ViewModelBase : ExtendedBindableObject
  {

    public ViewModelBase(INavigationService navigationService)
    {

    }

    private bool _isBusy;

    public event PropertyChangedEventHandler PropertyChanged;

    public bool IsBusy
    {
        get => _isBusy;
        set
        {
            _isBusy = value;
            RaisePropertyChanged(() =>(IsBusy));
        }
    }

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

    public virtual Task InitializeAsync(object data)
    {
        return Task.FromResult(false);
    }
}

及以下是我的ExtendedBindableObject继承BindableObject

 public abstract class ExtendedBindableObject : BindableObject
{
    public void RaisePropertyChanged<T>(Expression<Func<T>> property)
    {
        var name = GetMemberInfo(property).Name;
        OnPropertyChanged(name);
    }



    private MemberInfo GetMemberInfo(Expression expression)
    {
        MemberExpression operand;
        LambdaExpression lambdaExpression = (LambdaExpression)expression;
        if (lambdaExpression.Body as UnaryExpression != null)
        {
            UnaryExpression body = (UnaryExpression)lambdaExpression.Body;
            operand = (MemberExpression)body.Operand;
        }
        else
        {
            operand = (MemberExpression)lambdaExpression.Body;
        }
        return operand.Member;
    }
}

Answer 1

能给我一个例子，说明如何在RaisePropertyChanged中二传手。

尝试将您的SpicesCategory模型更改为：

public class SpicesCategory :ExtendedBindableObject
{
    public long Id { get; set; }

    public bool IsSelected { get; set; }

    private string _name { get; set; }

    public string Name
    {
        get => _name;
        set
        {
            _name = value;
            RaisePropertyChanged(() => (Name));
        }
    }

    private Color _nameColor { get; set; }

    public Color NameColor
    {
        get => _nameColor;
        set
        {
            _nameColor = value;
            RaisePropertyChanged(() => (NameColor));
        }
    }
}

可绑定布局Xamarin形式的视图未刷新

1 个答案: