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[英]Updating UI when a property of an element of a static ObservableCollection is modified
[英]Static property not updating in UI
我花了最后一個小時試圖在google和stackoverflow中找到答案。 我遵循了不同的意見和建議,但到目前為止沒有任何效果。 我當前的代碼如下所示:
public class GlobalManager : ViewModelBase
{
static object _LockObject_GFS = new object();
static double _GlobalFontSize;
public static double GlobalFontSize
{
get
{
lock (_LockObject_GFS)
{
_GlobalFontSize = GetGlobalResource<double>(LambdaHelper.MemberToString(() => GlobalFontSize));
return _GlobalFontSize;
}
}
set
{
lock (_LockObject_GFS)
{
if (_GlobalFontSize != value)
{
_GlobalFontSize = value;
SetGlobalResource(value, LambdaHelper.MemberToString(() => GlobalFontSize));
NotifyStaticPropertyChanged(() => GlobalFontSize);
}
}
}
}
}
getter和setter都被調用。 NotifyStaticPropertyChanged
可以正常工作,並且我的用戶界面沒有更新。 我添加了一個TextBlock
來檢查它是否更新。 顯然不是。
<TextBlock Text="{Binding Path=(global:GlobalManager.GlobalFontSize), Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"/>
如果我在VM(當前DataContext)中定義了一個屬性,並將其綁定到TextBlock
,則它將使用當前值正確更新。
當前, Slider
的DependencyProperty
Value
已綁定到此屬性,以更新字體大小。 ( IsSnapToTickEnabled="True"
)
public double GlobalFontSize
{
get { return GlobalManager.GlobalFontSize; }
set { GlobalManager.GlobalFontSize = value; NotifyPropertyChanged(() => GlobalFontSize); }
}
如何使綁定與static屬性一起正常工作? StaticPropertyChanged
事件不為null。
StaticPropertyChanged?.Invoke(null, new PropertyChangedEventArgs(propertyName));
編輯1:
public static void NotifyStaticPropertyChanged(string propertyName)
{
StaticPropertyChanged?.Invoke(null, new PropertyChangedEventArgs(propertyName));
}
public static void NotifyStaticPropertyChanged<T>(Expression<Func<T> > property)
{
var expr = property.Body as MemberExpression;
if (expr == null)
throw new ArgumentException("Lambda does not contain member expression. () => MyClassOrObject.Property");
NotifyStaticPropertyChanged(expr.Member.Name);
}
確保您的GetGlobalResource
和SetGlobalResource
方法可以按預期工作,並且您的事件簽名正確。
您可以參考以下工作示例實現並將其與您的實現示例進行比較:
public class GlobalManager
{
static object _LockObject_GFS = new object();
static double _GlobalFontSize;
public static double GlobalFontSize
{
get
{
lock (_LockObject_GFS)
{
return _GlobalFontSize;
}
}
set
{
lock (_LockObject_GFS)
{
if (_GlobalFontSize != value)
{
_GlobalFontSize = value;
NotifyStaticPropertyChanged(()=> GlobalFontSize);
}
}
}
}
public static event EventHandler<PropertyChangedEventArgs> StaticPropertyChanged;
public static void NotifyStaticPropertyChanged(string propertyName)
{
StaticPropertyChanged?.Invoke(null, new PropertyChangedEventArgs(propertyName));
}
public static void NotifyStaticPropertyChanged<T>(Expression<Func<T>> property)
{
var expr = property.Body as MemberExpression;
if (expr == null)
throw new ArgumentException("Lambda does not contain member expression. () => MyClassOrObject.Property");
NotifyStaticPropertyChanged(expr.Member.Name);
}
}
編輯:如果事件是在基類中定義的,則不起作用。
public abstract class MyBaseViewModel
{
public static event EventHandler<PropertyChangedEventArgs> StaticPropertyChanged;
public static void NotifyStaticPropertyChanged(string propertyName)
{
StaticPropertyChanged?.Invoke(null, new PropertyChangedEventArgs(propertyName));
}
public static void NotifyStaticPropertyChanged<T>(Expression<Func<T>> property)
{
var expr = property.Body as MemberExpression;
if (expr == null)
throw new ArgumentException("Lambda does not contain member expression. () => MyClassOrObject.Property");
NotifyStaticPropertyChanged(expr.Member.Name);
}
}
public class GlobalManager : MyBaseViewModel
{
static object _LockObject_GFS = new object();
static double _GlobalFontSize = 10.0;
public static double GlobalFontSize
{
get
{
lock (_LockObject_GFS)
{
return _GlobalFontSize;
}
}
set
{
lock (_LockObject_GFS)
{
if (_GlobalFontSize != value)
{
_GlobalFontSize = value;
NotifyStaticPropertyChanged("GlobalFontSize");
}
}
}
}
}
必須在屬性所在的同一類中定義StaticPropertyChangedEvent
,以使綁定得以更新:
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