[英]Problem in Changing the Background color of label on Button Click in MVVM WPF
[英]MVVM changing grid's background color on click
我是MVVM模式的真正初學者。 我正試圖在按鈕的點擊上更改網格的背景。 我有一個包含按鈕的網格的xaml,以及一個ViewModel .cs,我希望在按鈕的單擊時更改網格的背景。 直到我點擊時才能成功顯示MessageBox ...
.xaml代碼:
<Window x:Class="WpfSimple.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:WpfSimple"
Title="MainWindow" Height="150" Width="370">
<Window.DataContext>
<local:MainWindowViewModel/>
</Window.DataContext>
<Grid>
<Button Content="Click"
Height="23"
HorizontalAlignment="Left"
Background="Gray"
Margin="75.944,47.465,0,0"
Name="btnClick"
VerticalAlignment="Top"
Width="203"
Command="{Binding ButtonCommand}"/>
<!--What is necessary to add for changing grid color ? Commandparameter ?-->
</Grid>
MainWindowViewModel.cs代碼:
namespace WpfSimple
{
class MainWindowViewModel
{
private ICommand m_ButtonCommand;
public ICommand ButtonCommand
{
get
{
return m_ButtonCommand;
}
set
{
m_ButtonCommand = value;
}
}
public MainWindowViewModel()
{
ButtonCommand=new RelayCommand(new Action<object>(ChangeBgColor));
}
public void ChangeBgColor(object obj)
{
/*HERE I WANT TO CHANGE GRID COLOR*/
}
}
}
對不起,我的英語不好。
最好的祝福。
最適合你應該在ViewModel中實現INotifyPropertyChanged :
public class MainWindowViewModel : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
// This method is called by the Set accessor of each property.
// The CallerMemberName attribute that is applied to the optional propertyName
// parameter causes the property name of the caller to be substituted as an argument.
private void NotifyPropertyChanged([CallerMemberName] String propertyName = "")
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
}
然后,將NotifyPropertyChanged()添加到屬性設置器。
好。 接下來,將具有網格背景顏色的新Property添加到ViewModel:
private Brush _gridBackground;
public Brush GridBackground
{
get { return _gridBackground; }
set
{
_gridBackground = value;
NotifyPropertyChanged();
}
}
並將您的網格背景綁定到您的財產:
<Grid Background="{Binding GridBackground}">
最后,您只需在命令處理程序中更改GridBackground:
public void ChangeBgColor(object obj)
{
GridBackground = Brushes.Blue;
}
您應該記住,將諸如Brush之類的WPF類添加到代碼中是一種不好的做法。 更好的方法是在XAML代碼中使用IValueConverter ,在ViewModel中使用BCL類。 例如,您可以在ViewModel中使用枚舉並將其轉換為ValueConverter中的畫筆。
為ViewModel的屬性添加新的枚舉:
public enum GridState { Valid, Invalid }
更改屬性類型:
private GridState _gridBackground; public GridState GridBackground { get { return _gridBackground; } set { _gridBackground = value; NotifyPropertyChanged(); } }
添加帶有值轉換器的新類
public class GridStateToBackgroundColorConverter : IValueConverter { #region IValueConverter Members public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture) { GridState val = (GridState) value; if(val == GridState.Valid) return Brushes.Green; return Brushes.Red; } public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture) { throw new NotSupportedException(); } #endregion }
向控件添加新的靜態資源
<UserControl.Resources> <converters:GridStateToBackgroundColorConverter x:Key="gridStateToBackgroundColorConverter" /> </UserControl.Resources>
更新綁定到您的屬性
<Grid Background="{Binding GridBackground, Converter={StaticResource gridStateToBackgroundColorConverter}">
如果要更改網格背景顏色,則可以使用命令參數。 您可以將任何UI控件作為Command參數傳遞。 在您的情況下,傳遞網格以訪問視圖模型中的網格。 將名稱賦給網格並使用該名稱作為命令參數。 為此,您需要實現如下代碼:
<Window x:Class="WpfSimple.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:WpfSimple"
Title="MainWindow" Height="150" Width="370">
<Window.DataContext>
<local:MainWindowViewModel/>
</Window.DataContext>
<Grid Name="grid">
<Button Content="Click"
Height="23"
HorizontalAlignment="Left"
Background="Gray"
Margin="75.944,47.465,0,0"
Name="btnClick"
VerticalAlignment="Top"
Width="203"
Command="{Binding ButtonCommand}"
CommandParameter="{Binding Elementname="grid"}"/>
</Grid>
對.xaml文件進行此更改后。 實現參數化中繼命令以使用此傳遞的Grid在Viewmodel文件中使用。 實現參數化中繼命令嘗試實現以下代碼:
private ICommand m_ButtonCommand;
public ICommand ButtonCommand
{
get
{
return m_ButtonCommand;
}
set
{
m_ButtonCommand = value;
}
}
public MainWindowViewModel()
{
ButtonCommand=new RelayCommand<Grid>(ChangeBgColor);
}
public void ChangeBgColor(Grid grid)
{
if(grid!=null)
grid.Background = Brushes.Red; //Any color you want to change.
}
我希望這會奏效。 謝謝。
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