當方法調用時，矩形不會向上移動

Question

我現在正在使用圖形，並且正在嘗試創建一個隨關鍵事件一起移動的矩形。 下面是代碼：

類來創建矩形：

using System; 
using System.Collections.Generic; 
using System.Drawing; 
using System.Linq; 
using System.Text; 
using System.Threading.Tasks; 

namespace Snake 
{ 
class RectangleClass 
{ 
    // private Rectangle _rectangle; 
    private int _positionX; 
    private int _positionY; 
    private int _height; 
    private int _width; 



    public RectangleClass(int positionX, int positionY, int height, int width) 
    { 
     _positionX = positionX; 
     _positionY = positionY; 
     _height = height; 
     _width = width; 
    } 
    public int PositionX 
    { 
     get 
     { 
      return _positionX; 
     } 
     set 
     { 
      _positionX = value; 
     } 
    } 

    public int PositionY 
    { 
     get 
     { 
      return _positionY; 
     } 
     set 
     { 
      _positionY = value; 
     } 
    } 

    public int Height 
    { 
     get 
     { 
      return _height; 
     } 
     set 
     { 
      _height = value; 
     } 
    } 

    public int Width 
    { 
     get 
     { 
      return _width; 
     } 
     set 
     { 
      _width = value; 
     } 
    } 


    public Rectangle CreateRectangle() 
    { 
     Rectangle rectangle = new Rectangle(PositionX, PositionY, Width, Height); 
      return rectangle; 
    } 



    public int MoveYUpWard() 
    { 
     return PositionY += 10; 
    } 

    public int MoveYDownWard() 
    { 
     return PositionY -= 10; 
    } 


    } 
} 

和形式：

using System; 
    using System.Collections.Generic; 
    using System.ComponentModel; 
    using System.Data; 
    using System.Drawing; 
    using System.Linq; 
    using System.Text; 
    using System.Threading.Tasks; 
    using System.Windows.Forms; 


    namespace Snake 
    { 
     public partial class Form1 : Form 
     { 
      RectangleClass rc; 

      public Form1() 
      { 



       InitializeComponent(); 
       rc = new RectangleClass(30, 90, 50, 50); 

      } 

      private Graphics g; 



      private void Form1_Paint(object sender, PaintEventArgs e) 
      { 




       if (g == null) 
       { 
        g = this.CreateGraphics(); 
       } 
       Pen pen = new Pen(Color.Blue, 10); 
       g.DrawRectangle(pen, rc.CreateRectangle()); 

      } 



      private void Form1_KeyUp(object sender, KeyEventArgs e) 
      { 
       if (e.KeyCode == Keys.Up) 
       { 
        MessageBox.Show("UP"); 
        //Sets position y to 100 
        rc.MoveYUpWard(); 




       } 
      } 

我已調試的代碼，並且該方法MoveYUpWard（）不改變的位置當按下箭頭鍵時，矩形的位置相同。

我將不勝感激。

Answer 1

可能是問題在這裏。試試這個代碼。

public int MoveYUpWard() 
{ 
    PositionY -= 10; 
    return PositionY; 
} 

public int MoveYDownWard() 
{ 
    PositionY += 10; 
    return PositionY; 
} 


private void Form1_KeyUp(object sender, KeyEventArgs e) 
{ 
    if (e.KeyCode == Keys.Up) 
    { 
     MessageBox.Show("UP"); 
     //Sets position y to 100 
     rc.MoveYUpWard(); 
     this.Invalidate(); 
    } 
}