XAML数据触发器未更新

当数据源中的属性更改时，我尝试更改按钮的颜色。根据

IsFilterOn

属性的初始值，初始化背景色可以正常工作，但当属性更改时，背景色不会更新

XAML

<FlexLayout BindableLayout.ItemsSource="{Binding Filters}">
    <BindableLayout.ItemTemplate>
        <DataTemplate>
            <Button>
                <Button.Triggers>
                    <DataTrigger Binding="{Binding IsFilterOn}" TargetType="Button" Value="False">
                        <Setter Property="BackgroundColor" Value="{Binding UpColour}" />
                    </DataTrigger>
                    <DataTrigger Binding="{Binding IsFilterOn}" TargetType="Button" Value="True">
                        <Setter Property="BackgroundColor" Value="{Binding DownColour}" />
                    </DataTrigger>
                </Button.Triggers>
            </Button>
        </DataTemplate>
    </BindableLayout.ItemTemplate>
</FlexLayout>

---

点击按钮可正确更新按钮的

IsFilterOn

属性（未显示代码），但用户界面不会改变以反映该属性。我做错了什么？

我们看不到您如何将

IsFilterOn

属性从

true

更新为

false

，但是如果您直接更改列表中某个

FilterModel

实例的属性，则不会调用属性更改事件

当您从列表中添加或删除某些内容时，

ObservableCollection

将执行属性更改事件，但它不监视对象的属性

您有两个选项，要么在更新

IsFilterOn

时从

FilterModel

调用属性更改事件，要么更改所有需要更改的属性值，然后手动执行列表上的属性更改。如果同时更新多个

FilterModel

s，则使用第二个选项可能会提高性能

备选案文1：

public class FilterModel : INotifyPropertyChanged {
    public string UpColour { get; set; }
    public string DownColour { get; set; }

    private bool _isFilterOn = false;
    public bool IsFilterOn {
        get { return _isFilterOn; }
        set {
            _isFilterOn = value;
            NotifyPropertyChanged(); // Anytime this property is changed Property Changed will be executed
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;
    private void NotifyPropertyChanged([System.Runtime.CompilerServices.CallerMemberName] string propertyName = "")
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
    }
}

备选案文2：

public class FilterViewModel {
    private ObservableCollection<FilterModel> _filters;
    public ObservableCollection<FilterModel> Filters {
        get => _filters ?? (_filters = new ObservableCollection<FilterModel>());
        set {
            _filters = value;
            NotifyPropertyChanged();
        }
    }

    public void ToggleFilters() {
        // some logic

        Filters[0].IsFilterOn = true; // Make all property changes

        NotifyPropertyChanged(nameof(Filters)); // Tell the UI that the list has been updated and to refresh the data
    }

    public event PropertyChangedEventHandler PropertyChanged;
    private void NotifyPropertyChanged([System.Runtime.CompilerServices.CallerMemberName] string propertyName = "")
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
    }
}

公共类FilterViewModel{
私有可观测收集过滤器；
公共可观测收集过滤器{
get=>\u filters？？？（\u filters=newobservetecollection（））；
设置{
_过滤器=值；
NotifyPropertyChanged（）；
}
}
公共无效切换过滤器（）{
//一些逻辑
筛选器[0]。IsFilterOn=true；//进行所有属性更改
NotifyPropertyChanged（nameof（Filters））；//告诉UI列表已更新，并刷新数据
}
公共事件属性更改事件处理程序属性更改；
私有void NotifyPropertyChanged（[System.Runtime.CompilerServices.CallerMemberName]字符串propertyName=”“）
{
if（PropertyChanged！=null）
{
PropertyChanged（这是新的PropertyChangedEventArgs（propertyName））；
}
}
}

很可能是因为更改UI的函数未在UI线程上调用/运行。如果看不到您拥有的UI代码/您试图更新的UI代码，就很难提供更多帮助。“Device.beginInvokeMainThread”检查：您是正确的。那有点像掌心时刻，谢谢你的提醒。添加了PropertyChanged.Fody，一切都开始工作了。

public class FilterViewModel {
    private ObservableCollection<FilterModel> _filters;
    public ObservableCollection<FilterModel> Filters {
        get => _filters ?? (_filters = new ObservableCollection<FilterModel>());
        set {
            _filters = value;
            NotifyPropertyChanged();
        }
    }

    public void ToggleFilters() {
        // some logic

        Filters[0].IsFilterOn = true; // Make all property changes

        NotifyPropertyChanged(nameof(Filters)); // Tell the UI that the list has been updated and to refresh the data
    }

    public event PropertyChangedEventHandler PropertyChanged;
    private void NotifyPropertyChanged([System.Runtime.CompilerServices.CallerMemberName] string propertyName = "")
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
    }
}