使用触发器更改 XAML 地图图钉的背景色

Question

我正在尝试使用数据模板触发器更改 XAML 地图图钉的背景颜色，但也许我的代码中有问题。这个想法是，地图的 ItemSource 绑定到图钉模型的可观察集合，当属性 IsOnline 的值为真时，图钉应变为绿色。

这是我Geolocation.xaml：

<m:Map CredentialsProvider="XXX" Mode="Road">
<m:MapItemsControl Name="Pushpins" ItemsSource="{Binding PushpinCollection}" >
<m:MapItemsControl.ItemTemplate>
<DataTemplate>
<m:Pushpin Location="{Binding Path=Location}" />
<DataTemplate.Triggers>
<DataTrigger Binding="{Binding Path=IsOnline}" Value="True">
<Setter Property="m:Pushpin.Background" Value="Green"></Setter>
</DataTrigger>
</DataTemplate.Triggers>
</DataTemplate>
</m:MapItemsControl.ItemTemplate>
</m:MapItemsControl>
</m:Map>

这是视图模型GeolocationViewModel.cs：

namespace MyNamespace
{
internal class Pushpins : ObservableCollection<PushpinModel> { }
internal class PushpinModel
{
public PushpinModel(double latitude, double longitude)
{
Location = new Location(latitude, longitude);
}
public Location Location { get; set; }
public bool IsOnline { get; set; } = false;
}
internal class GeolocationViewModel : INotifyPropertyChanged
{
public GeolocationViewModel()
{
pushpinCollection = new Pushpins();
CreatePushpins();
}
private Pushpins pushpinCollection;
public Pushpins PushpinCollection
{
get { return pushpinCollection;  }
}
private void CreatePushpins()
{
Random rnd = new Random();
for (int i = 1; i <= 100; i++)
{
PushpinModel pin = new PushpinModel(rnd.NextDouble() * 180 - 90, rnd.NextDouble() * 360 - 180);
if (rnd.NextDouble() >= 0.5)
pin.IsOnline = true;
pushpinCollection.Add(pin);
}
OnPropertyChanged("PushpinCollection");
}
#region IPropertyChange
public event PropertyChangedEventHandler PropertyChanged;
protected void OnPropertyChanged(string propertyName)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
#endregion
}
}

我对SetterProperty有一些疑问，因为我认为我没有更改正确的项目。

有什么建议吗？谢谢你们！

Answer 1

最后我找到了一种使用Style.Triggers更改图钉颜色的方法。 这是工作Geolocation.xaml：

<m:Map CredentialsProvider="XXX" Mode="Road">
<m:MapItemsControl Name="Pushpins" ItemsSource="{Binding PushpinCollection}" >
<m:MapItemsControl.ItemTemplate>
<DataTemplate>
<m:Pushpin Location="{Binding Path=Location}" />
<m:Pushpin.Style>
<Style TargetType="m:Pushpin">
<Setter Property="Background" Value="Red" />
<Style.Triggers>
<DataTrigger Binding="{Binding IsOnline}" Value="True">
<Setter Property="Background" Value="Green" />
</DataTrigger>
</Style.Triggers>
</Style>
<m:Pushpin.Style>
</DataTemplate>
</m:MapItemsControl.ItemTemplate>
</m:MapItemsControl>
</m:Map>

和GeolocationViewModel.cs的工作版本：

namespace MyNamespace
{
internal class Pushpins : ObservableCollection<Pushpin> { }
internal class Pushpin : INotifyPropertyChanged
{
public Pushpin(double latitude, double longitude)
{
Location = new Location(latitude, longitude);
IsOnline = false;
}
public Location Location { get; set; }
private bool isOnline;
public bool IsOnline
{ 
get { return isOnline; }
set
{
isOnline = value;
OnPropertyChanged("IsOnline");
}
}
#region IPropertyChange
public event PropertyChangedEventHandler PropertyChanged;
protected void OnPropertyChanged(string propertyName)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
#endregion
}
internal class GeolocationViewModel : INotifyPropertyChanged
{
public GeolocationViewModel()
{
pushpinCollection = new Pushpins();
CreateRandomPushpins();
}
private Pushpins pushpinCollection;
public Pushpins PushpinCollection
{
get { return pushpinCollection;  }
}
private void CreateRandomPushpins()
{
Random rnd = new Random();
for (int i = 1; i <= 100; i++)
{
PushpinModel pin = new PushpinModel(rnd.NextDouble() * 180 - 90, rnd.NextDouble() * 360 - 180);
if (rnd.NextDouble() >= 0.5)
pin.IsOnline = true;
pushpinCollection.Add(pin);
}
OnPropertyChanged("PushpinCollection");
}
#region IPropertyChange
public event PropertyChangedEventHandler PropertyChanged;
protected void OnPropertyChanged(string propertyName)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
#endregion
}
}