我正在尝试学习MVVM样式更新.不是那么游泳.
我不得不更新一个基于对Point Collection的更改而绘制的简单矩形.
在初始化时,UI更新,但在对Point Collection进行简单更改后,UI中的路径不会更新.
我添加了一些TextBlock来确保Change事件被触发,但此时我有点迷失.
任何帮助赞赏：
XAML：
<Window
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:ExampleGreg" x:Class="ExampleGreg.MainWindow"
Title="MainWindow" Height="161.614" Width="324.087">
<Grid x:Name="gridUser" MouseDown="click_MouseDown" >
<Canvas x:Name="MeterCanvas" Margin="14,7,30,0" Background="#FFAFAFAF" Height="35" VerticalAlignment="Top">
<Path stroke="Black" strokeThickness="2">
<Path.Data>
<PathGeometry x:Name="geometry"/>
</Path.Data>
</Path>
<Path stroke="Black" strokeThickness="2">
<Path.Data>
<PathGeometry x:Name="polylinePwr">
<PathGeometry.Transform>
<ScaleTransform ScaleX="{Binding ActualWidth,ElementName=MeterCanvas}" ScaleY="{Binding ActualHeight,ElementName=MeterCanvas}" />
</PathGeometry.Transform>
<PathGeometry.figures>
<Pathfigure IsClosed ="True" StartPoint="{Binding Path=thePoints[0]}">
<Pathfigure.Segments>
<PathSegmentCollection>
<polyLinesegment Points="{Binding thePoints,UpdateSourceTrigger=PropertyChanged}" />
</PathSegmentCollection>
</Pathfigure.Segments>
</Pathfigure>
</PathGeometry.figures>
</PathGeometry>
</Path.Data>
</Path>
</Canvas>
<Label Content="{Binding thePoints[0]}" Margin="14,58,199.6,0" VerticalAlignment="Top" Height="30" BorderThickness="1"/>
<Label Content="{Binding thePoints[1]}" Margin="14,88,0" VerticalAlignment="Top" Height="30" BorderThickness="1"/>
<Label Content="{Binding thePoints[2]}" Margin="165,29.6,0" VerticalAlignment="Top" Height="30" BorderThickness="1"/>
<Label Content="{Binding thePoints[3]}" Margin="165,93,0" VerticalAlignment="Top" Height="30" BorderThickness="1"/>
</Grid>
</Window>
主窗口：
public partial class MainWindow : Window
{
private Mainviewmodel mvm;
public MainWindow()
{
InitializeComponent();
mvm = new Mainviewmodel();
this.DataContext = mvm;
}
private void click_MouseDown(object sender,MouseButtonEventArgs e)
{
mvm.theText = mvm.theText + ".";
mvm.ChangePoint(.4);
}
}
模型视图：
class Mainviewmodel : INotifyPropertyChanged { private string _theText = "Initial"; private PointCollection _points = new PointCollection(); private polyLinesegment segment; public event PropertyChangedEventHandler PropertyChanged; private void OnPropertyChanged(String info) { PropertyChangedEventHandler handler = PropertyChanged; if (handler != null) { handler(this,new PropertyChangedEventArgs(info)); } } public Mainviewmodel() { ChangePoint(0.9); } public string theText { get { return _theText; } set { if (_theText != value) { _theText = value; OnPropertyChanged("theText"); } } } public PointCollection thePoints { get { return _points; } } public void ChangePoint(double x) { _points.Clear(); AddPoint(new Point(0.2,0.2)); AddPoint(new Point(0.2,0.8)); AddPoint(new Point(x,0.2)); OnPropertyChanged("thePoints"); _theText = _theText + "!"; OnPropertyChanged("theText"); } public void AddPoint(Point p) { _points.Add(p); } }
谢谢你的任何建议(工作:))
– 以下的答案 –
我添加了一个IValueConverter类：
public class PointCollectionConverter : IValueConverter
{
#region IValueConverter Members
public object Convert(object value,System.Type targettype,object parameter,System.Globalization.CultureInfo culture)
{
if (value.GetType() == typeof(ObservableCollection<Point>) && targettype == typeof(PointCollection))
{
var pointCollection = new PointCollection();
foreach (var point in value as ObservableCollection<Point>)
pointCollection.Add(point);
return pointCollection;
}
return null;
}
public object ConvertBack(object value,System.Globalization.CultureInfo culture)
{
return null; //not needed
}
#endregion
}
并将ModelView更改为使用Observable Collection …
更新了ModelView：
class Mainviewmodel : INotifyPropertyChanged { private string _theText = "Initial"; private ObservableCollection<Point> _points; public event PropertyChangedEventHandler PropertyChanged; private void OnPropertyChanged(String info) { PropertyChangedEventHandler handler = PropertyChanged; if (handler != null) { handler(this,new PropertyChangedEventArgs(info)); } } public Mainviewmodel() { _points = new ObservableCollection<Point>(); _points.Add(new Point(0.2,0.2)); _points.Add(new Point(0.2,0.8)); } public string theText { get { return _theText; } set { if (_theText != value) { _theText = value; OnPropertyChanged("theText"); } } } public ObservableCollection<Point> thePoints { get { return _points; } } double xAdder = 0; double y = 0.0; public void ChangePoint(double x) { y = y + .1; if (y > .9) { y = .1; xAdder += .1; } _points.Add(new Point(x+xAdder,y)); OnPropertyChanged("thePoints"); _theText = _theText + "!"; OnPropertyChanged("theText"); } }
并更新了XAML：
<Window
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:ExampleGreg" x:Class="ExampleGreg.MainWindow"
Title="MainWindow" Height="161.614" Width="324.087">
<Window.Resources>
<local:PointCollectionConverter x:Key="pointCollectionConverter"/>
</Window.Resources>
<Grid x:Name="gridUser" MouseDown="click_MouseDown" >
<Canvas x:Name="MeterCanvas" Margin="14,0" Background="#FFAFAFAF" Height="35" VerticalAlignment="Top">
<Path stroke="Black" strokeThickness="2">
<Path.Data>
<PathGeometry x:Name="geometry"/>
</Path.Data>
</Path>
<Path stroke="Black" strokeThickness="2">
<Path.Data>
<PathGeometry x:Name="polylinePwr">
<PathGeometry.Transform>
<ScaleTransform ScaleX="{Binding ActualWidth,ElementName=MeterCanvas}" />
</PathGeometry.Transform>
<PathGeometry.figures>
<Pathfigure StartPoint="{Binding Path=thePoints[0],Converter={StaticResource pointCollectionConverter}}">
<Pathfigure.Segments>
<PathSegmentCollection>
<polyLinesegment Points="{Binding thePoints,Converter={StaticResource pointCollectionConverter}}" />
</PathSegmentCollection>
</Pathfigure.Segments>
</Pathfigure>
</PathGeometry.figures>
</PathGeometry>
</Path.Data>
</Path>
</Canvas>
<Label Content="{Binding thePoints[0]}" Margin="14,0" VerticalAlignment="Top" Height="30" BorderThickness="1"/>
<Label Content="{Binding thePoints[1]}" Margin="14,0" VerticalAlignment="Top" Height="30" BorderThickness="1"/>
<Label Content="{Binding thePoints[2]}" Margin="165,0" VerticalAlignment="Top" Height="30" BorderThickness="1"/>
<Label Content="{Binding thePoints[3]}" Margin="165,0" VerticalAlignment="Top" Height="30" BorderThickness="1"/>
</Grid>
鉴于IValueConverter创建了一个新的PointCollection,我不确定我是否会获得任何性能提升.每个ObservableCollection都会被更改.
感谢大家帮助我完成这项工作.我希望将完整的代码粘贴为有效,如果有其他人遇到同样的事情.
编辑#2 – 在Observable w / IValueConverter与copying PointCollection对新PointCollection进行基准测试后,Point Collection看起来更快：
// Option 2 - WAY Faster.
// Just Use a Points Collection,copy it,and add a point.
public void AddPoint2(Point pt)
{
PointCollection pc = new PointCollection(_points2);
pc.Add(new Point(pt.X,pt.Y));
_points2 = pc;
OnPropertyChanged("thePoints2");
}
来自
// 5000 point sinwave for testing
foreach (Point pt in sinWave) mvm.AddPoint2(pt);
x++;
如果有更好的方式,评论赞赏.
解决方法
尝试替换属性,而不是清除重新填充它.
public void ChangePoint(double x)
{
var newPoints = new PointCollection();
newPoints.Add(new Point(0.2,0.2));
newPoints.Add(new Point(0.2,0.8));
newPoints.Add(new Point(x,0.2));
OnPropertyChanged("thePoints");
_theText = _theText + "!";
OnPropertyChanged("theText");
}
如果对象引用相同,绑定似乎有时会忽略“PropertyChanged”事件.
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