Question

我已经创建了一个与自定义Xamarin Forms Map相关的ViewModel

在此地图上，我正在根据条件在触发器上显示一个Entry字段

我已成功将Entry IsVisible参数绑定到该行为，并且可以在按钮上进行切换

但是，我真正想要实现的是响应于单击图钉

尝试此操作时，无法触发OnPropertyChange

我不确定如何克服这一点-引脚位于单独的类中，因此我无法将其绑定到包含文本项的Grid视图中

我已将click事件附加到自定义图钉，并使用它与视图模型进行交互

        pin.Clicked += (object sender, EventArgs e) =>
        {
            var p = sender as CustomPin;

            var callingMethod = new HandleEditor();

            callingMethod.Pin_Clicked(p);

        };

这是XAML

    <Grid x:Name="LayoutGrid">

    <Grid.BindingContext>
        <local:HandleEditor />
    </Grid.BindingContext>

<Grid.RowDefinitions>
    <RowDefinition Height="*" />
    <RowDefinition Height="150" />
    <RowDefinition Height="*" />     
</Grid.RowDefinitions>

    <local:CustomMap Grid.RowSpan="3"  Grid.Row="0"  MapType="Street" WidthRequest="300" HeightRequest="300" />                        

    <Editor x:Name="TextEntry" Grid.Row="1" VerticalOptions="FillAndExpand" IsVisible="{Binding SwitchVisible, Mode=TwoWay}"/>

    <Button Grid.Row="2" Text="Switch Bool Test" Command="{Binding ChangeBoolValue}"/>

    </Grid>

这是ViewModel

    public event PropertyChangedEventHandler PropertyChanged;

    bool isEditorVisible = false;

    public ICommand ChangeBoolValue { protected set; get; }
    public ICommand Debug { protected set; get; }


    public bool SwitchVisible

    {



        get

        {

            System.Diagnostics.Debug.WriteLine("Debug: SwitchVisible has been fired " + isEditorVisible);
            return isEditorVisible;

        }



    }




    public HandleEditor()


    {


        ChangeBoolValue = new Command(() =>
        {


            if (isEditorVisible == true)

            {

                isEditorVisible = false;
                OnPropertyChanged("SwitchVisible");
            }

            else
            {

                isEditorVisible = true;
                OnPropertyChanged("SwitchVisible");

            }


        });


    }


    protected virtual void OnPropertyChanged(string propertyName)
    {
        System.Diagnostics.Debug.WriteLine("Debug: OnPropertyChanged has been fired " + propertyName + " : " + isEditorVisible);

        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }

    public void Pin_Clicked(CustomPin pin)

    {


        isEditorVisible = true;
        OnPropertyChanged("SwitchVisible");


    }

Answer 1

所以我可能会错过一些东西，但是我看不到isEditorVisible属性的用途。

我已经成功将Entry IsVisible参数绑定到了行为，并可以在按钮上进行切换

您使用的是Editor，而不是Entry。另外，您将按钮的Command属性绑定到Command中的ViewModel中的ChangeBoolValue。您没有使用Behavior<T>，或者您在代码段中未添加它:)。

<Editor x:Name="TextEntry" Grid.Row="1" VerticalOptions="FillAndExpand" IsVisible="{Binding SwitchVisible, Mode=TwoWay}"/>

所以您要实现的是Editor IsVisibleProperty根据SwitchIsVisible属性进行更改，这是您要绑定的属性，对吗？

我会在ViewModel中执行类似的操作，而不是实际的实现：

public event PropertyChangedEventHandler PropertyChanged;

public ICommand ChangeBoolValue { protected set; get; }
public ICommand Debug { protected set; get; }

private bool _switchVisible;
public bool SwitchVisible
{

    get => _switchVisible;
    set
    {            
      if(_switchVisible == value) return;
      _switchVisible = value;
      OnPropertyChanged("SwitchVisible");
    }
}


public HandleEditor()
{
    ChangeBoolValue = new Command(() =>
    {
       SwitchVisible = !SwitchVisible;

    });
}


protected virtual void OnPropertyChanged(string propertyName)
{
    System.Diagnostics.Debug.WriteLine("Debug: OnPropertyChanged has been fired " + propertyName + " : " + isEditorVisible);

    PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}

public void Pin_Clicked(CustomPin pin)
{
   SwitchVisible = true;
}

Xamarin形式行为-与外部类的交互

1 个答案: