繪製一個橢圓，然後將其移動到另一個位置

Question

我得出使用EllipsePoints陣列限定橢圓的高度寬度和顏色的橢圓。

然後使用for循環使用橢圓點和一個隨機數來設置它的位置來得到橢圓的位置：

Random rand = new Random();  

Int32 randomNumber = rand.Next(0, 310); 
Int32 randomNumber2 = rand.Next(0, 500); 

for (int j = 0; j < 60; j++) 
{ 
    ellipsePoints[j] = new Ellipse() { Width = 20, Height = 20, Fill = Brushes.Red }; 

    canvas1.Children.Add(ellipsePoints[j]); 
} 

for (int i = 0; i < 60; i++) 
{ 
    Canvas.SetLeft(ellipsePoints[i], randomNumber2); 
    Canvas.SetTop(ellipsePoints[i], randomNumber); 
} 

我能做什麼做了一定量之後，橢圓消失時間，然後出現在另一個隨機的位置？

Answer 1

有這個問題2個的重要方面。

• 定時器 - 在WPF中我們使用System.Windows.Threading.DispatcherTimer。

• 刪除元素 - 的一種方法是將它添加到畫布之前維持UI元素的副本。我已經在一個類變量保存它，這樣我可以從畫布用以下方法後刪除它

  PaintCanvas.Children.Remove（橢圓形）;

創建你WPF和添加一個名爲帆布PaintCanvas

<Window x:Class="WpfApplication1.MainWindow" 
     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
     Title="MainWindow" Height="889" Width="1080"> 
    <Canvas Name="PaintCanvas"> 
     <Button Canvas.Left="46" Canvas.Top="274" Content="Button" Height="23" Name="button1" Width="75" Click="button1_Click" /> 
    </Canvas > 
</Window> 

的代碼。我已經記錄了它。

public partial class MainWindow : Window 
{ 
    int loopCounter; 
    private System.Windows.Threading.DispatcherTimer timer; 
    Random rand = new Random(); 
    Ellipse ellipse = null; 

    public MainWindow() 
    { 
     InitializeComponent(); 

     //Initialize the timer class 
     timer = new System.Windows.Threading.DispatcherTimer(); 
     timer.Interval = TimeSpan.FromSeconds(1); //Set the interval period here. 
     timer.Tick += timer1_Tick;    
    }  

    private void button1_Click(object sender, RoutedEventArgs e) 
    { 
     loopCounter = 10; 
     timer.Start(); 
    } 

    private void timer1_Tick(object sender, EventArgs e) 
    { 
     //Remove the previous ellipse from the paint canvas. 
     PaintCanvas.Children.Remove(ellipse); 

     if (--loopCounter == 0) 
      timer.Stop(); 

     //Add the ellipse to the canvas 
     ellipse=CreateAnEllipse(20,20); 
     PaintCanvas.Children.Add(ellipse); 

     Canvas.SetLeft(ellipse, rand.Next(0, 310)); 
     Canvas.SetTop(ellipse, rand.Next(0, 500)); 
    } 

    // Customize your ellipse in this method 
    public Ellipse CreateAnEllipse(int height,int width) 
    { 
     SolidColorBrush fillBrush = new SolidColorBrush() { Color = Colors.Red }; 
     SolidColorBrush borderBrush = new SolidColorBrush() { Color = Colors.Black }; 

     return new Ellipse() 
     { 
      Height = height, 
      Width = width, 
      StrokeThickness = 1, 
      Stroke = borderBrush, 
      Fill = fillBrush 
     };  
    } 
}