Как вызвать пользовательский элемент управления onpaint

Question

Я хочу вызвать событие OnPaint в своем настраиваемом элементе управления. Я создал класс и унаследованный элемент управления для создания настраиваемого элемента управления и хочу вызвать OnPaint или событие paint, когда объект инициализируется. Но когда я создаю событие paint класса, не запускается. Введите приведенный ниже код.

internal class CallRectangle : Control 
    { 

     public CallRectangle() 
     { 
      this.Paint += CalloutRectangle_Paint; 
     } 

     void CalloutRectangle_Paint(object sender, PaintEventArgs e) 
     { 
      throw new NotImplementedException(); 
     } 
     protected override void OnPaint(PaintEventArgs e) 
     { 

     }  
    } 


// Create object to the custom control and call paint event using constructor 

CallRectangle obj = new CallRectangle(); 
this.Controls.Add(obj); 

Любой, кто-нибудь, дайте мне знать, как назвать событие рисования.

Thanks, Bharathi.

Answer 1

Вызов недействителен, обновляется или обновляется не будет работать для вас.

Вот загружаемое Sample from Microsoft с гидом Шаг за шагом на как к наследованию непосредственно от контроля и строить Задерните События, так как унаследовав от существующего управления (кнопки, скажем) довольно легко, как уже делает это сам.

Что вы увидите в приведенном выше примере, вам нужно будет создать несколько событий рисования на основе сложности вашего элемента управления (например, окна списка, в котором есть элементы, которые нужно рисовать). Пример код из выше ссылки:

/// <include file='DocumentationComments.xml' path='doc/members/member[@name="M:TwoLineListBox.OnPaint"]/*'/> 
     protected override void OnPaint(PaintEventArgs e) 
     { 
      base.OnPaint(e); 
      // draw on memory bitmap 
      CreateMemoryBitmap(); 

      // TODO: Figure out how to avoid doing this on every paint 
      // calculate fields required to layout and draw list 
      RecalcItems(e.Graphics); 

      Graphics g = Graphics.FromImage(m_bmp); 

      // Draw the background and raise the PaintBackground event 
      OnPaintBackground(new ListPaintEventArgs(g)); 

      // draw list 
      if (m_list != null) 
       DrawItems(g); 

      // Draw the frame around the list 
      Rectangle rc = new Rectangle(0, 0, this.Width - m_scrollBarWidth, this.Height - 1); 
      g.DrawRectangle(new Pen(Color.Black), rc); 

      // blit memory bitmap to screen 
      e.Graphics.DrawImage(m_bmp, 0, 0); 
     } 

     // This prevents the base class from doing OnPaintBackground. 
     // Since the OnPaint method paints the entire window there's no reason 
     // to let this go through. If we do it'll cause flashing. 
     /// <include file='DocumentationComments.xml' path='doc/members/member[@name="M:TwoLineListBox.OnPaintBackground"]/*'/> 
     protected override void OnPaintBackground(PaintEventArgs e) 
     { 
     } 

     // Called when it is time to draw the background. To take complete control of background 
     // drawing override this. To get called after the background is drawn by the base class 
     // register for the PaintBackground event. 
     /// <include file='DocumentationComments.xml' path='doc/members/member[@name="M:TwoLineListBox.OnPaintBackgroundII"]/*'/> 
     protected virtual void OnPaintBackground(ListPaintEventArgs e) 
     { 
      // Fill the background with the background colour 
      e.Graphics.Clear(this.BackColor); 
      if (PaintBackground != null) 
       PaintBackground(this, e); 
     } 

     // Called to draw a line item. To take complete control of drawing an item override this method. 
     // To let the base class draw the item first and then do your own additional work register for the 
     // PaintItem event. 
     /// <include file='DocumentationComments.xml' path='doc/members/member[@name="M:TwoLineListBox.OnPaintItem"]/*'/> 
     protected virtual void OnPaintItem(ListPaintEventArgs e) 
     { 

      Graphics g = e.Graphics; 
      Rectangle destRect = new Rectangle(); // Destination for the item image, if any 
      Rectangle srcRect = new Rectangle(); // Source region of the image to draw 
      Rectangle textRect = new Rectangle(); // Destination for the text 
      int lineIndent = 0;      // How far the text is moved in from the left margin before drawing 
      Image imageToDraw = null; 
      string line1Text; 
      string line2Text; 

      // On the null case skip everything and just draw the separator line 
      if (e.Item == null) 
       goto DrawSeparator; 


      line1Text = GetStringProperty(e.Item, this.m_line1Property); 
      if (line1Text == null) 
       line1Text = e.Item.ToString(); 

      line2Text = GetStringProperty(e.Item, this.m_line2Property); 
      if (line2Text == null) 
       line2Text = e.Item.ToString(); 


      // Figure out if we're drawing an image per item from the object, or one for 
      // everything 
      imageToDraw = GetImageProperty(e.Item, this.m_itemImageProperty); 
      if (imageToDraw == null) 

       imageToDraw = m_itemImage; 

      // Calculate the position of the item image, if we have one, and the line indents 
      if (imageToDraw != null) 
      { 

       srcRect.X = 0; 
       srcRect.Y = 0; 
       srcRect.Width = imageToDraw.Width; 
       srcRect.Height = imageToDraw.Height; 

       // int vertPos = (m_itemHeight - m_itemImage.Height)/2; 
       destRect.X = e.ClipRectangle.X + IMAGE_PADDING_X; 
       destRect.Y = e.ClipRectangle.Y + IMAGE_PADDING_Y; 
       // destRect.Y = (vertPos < 0) ? 0 : vertPos; // Center the image vertically in the line height. Handle the image being larger than the item height 

       // Account for an image that is taller than the item height 
       destRect.Height = (imageToDraw.Height > m_itemHeight - IMAGE_PADDING_Y) ? m_itemHeight - (IMAGE_PADDING_Y * 2) : imageToDraw.Height; 
       destRect.Width = destRect.Height; 
       // Set the text indent based on the image 
       lineIndent = IMAGE_PADDING_X + imageToDraw.Width + TEXT_PADDING_X; // Two pixels for the left indent of the image 
      } 
      else 
      { 
       // Set the text indent without using the image 
       lineIndent = TEXT_PADDING_X; 
      } 

      // Calculate the text rectangle 
      textRect.X = e.ClipRectangle.X + lineIndent; 
      textRect.Width = e.ClipRectangle.Width - TEXT_PADDING_X - textRect.X; // Allows for padding on the right edge too 
      textRect.Y = e.ClipRectangle.Y + 2; 
      textRect.Height = this.m_textHeightLine1; 

      // From here on we actually draw things. First the selected background, if necessary 
      if (e.Selected) 
       g.FillRectangle(m_brushSelBack, e.ClipRectangle); 

      // Draw the icon, if we have one 
      if (imageToDraw != null) 
      { 
       if (m_useTransparent) 

        g.DrawImage(imageToDraw, destRect, srcRect.Y, srcRect.Y, srcRect.Height, srcRect.Height, 
         GraphicsUnit.Pixel, m_imageAttributes); 
       else 
        g.DrawImage(imageToDraw, destRect, srcRect, GraphicsUnit.Pixel); 
      } 

      // Draw the text in a bounding rect to force it to truncate if too long 
      g.DrawString(line1Text, m_fontLine1, e.Selected ? m_brushSelText : m_brushText, textRect); 

      // Draw the second line 
      textRect.Y += m_textHeightLine1 + 3; 
      textRect.Height = this.m_textHeightLine2; 
      g.DrawString(line2Text, m_fontLine2, e.Selected ? m_brushSelText : m_brushText, textRect); 

     DrawSeparator: 
      // Draw the separator line 
      g.DrawLine(m_penSep, e.ClipRectangle.X, e.ClipRectangle.Y + e.ClipRectangle.Height, 
       e.ClipRectangle.X + e.ClipRectangle.Width, e.ClipRectangle.Y + e.ClipRectangle.Height); 

      // Let other people know it's time for them to draw 
      if (PaintItem != null) 
       PaintItem(this, e); 
     } 


     // Draw all the items. 
     private void DrawItems(Graphics g) 
     { 
      ListPaintEventArgs ListPaintEventArgs = new ListPaintEventArgs(g); 

      // Calculate our actual drawing area, accounting for the scroll bar 
      Rectangle rc = new Rectangle(0, 0, this.Width - m_scrollBarWidth, this.Height - 1); 

      // draw items that are visible 
      int curItem = 0; 
      for (int i = 0; (i < m_visibleCount); i++) 
      { 
       curItem = i + m_topItem; 
       if (curItem < m_list.Count) 
       { 
        // Calculate the drawing area for the item 
        ListPaintEventArgs.ClipRectangle = new Rectangle(rc.X, 
         rc.Y + (i * m_itemHeight), 
         rc.Width, 
         this.m_itemHeight); 

        // Get the item we'll be drawing with and whether it is selected      
        ListPaintEventArgs.Item = m_list[curItem]; 
        ListPaintEventArgs.Selected = (m_selItem == curItem); 

        // Draw the item 
        OnPaintItem(ListPaintEventArgs); 
       } 
      } 
     } 

     // Recalculates the heights and visible counts for assorted items 
     // in the listbox. 
     // TODO: Get rid of this method by moving the rest of the items into the assorted 
     // properties. 
     private void RecalcItems(Graphics g) 
     { 
      // The text heights for a single line of text is the height of the font. 
      m_textHeightLine1 = g.MeasureString("W", this.m_fontLine1).ToSize().Height; 
      m_textHeightLine2 = g.MeasureString("W", this.m_fontLine2).ToSize().Height; 

      // The height for an individual item is two lines plus some padding 
      m_itemHeight = m_textHeightLine1 + m_textHeightLine2 + 5; 

      m_visibleCount = this.Height/m_itemHeight; 

      // Set the top item to draw to the current scroll position 
      m_topItem = m_scrollValue; 
     } 

     // Creates all the objects we need for drawing 
     private void CreateGdiObjects() 
     { 
      m_brushText = new SolidBrush(this.ForeColor); 
      m_brushSelText = new SolidBrush(this.m_selForeColor); 
      m_brushSelBack = new SolidBrush(this.m_selBackColor); 
      m_penSep = new Pen(this.m_separatorColor); 
      m_imageAttributes = new ImageAttributes(); 
     } 

     // Creates a bitmap in memory to do our drawing. We'll draw on this first 
     // and then splat it to the screen. 
     private void CreateMemoryBitmap() 
     { 
      // Only create if don't have one and the size hasn't changed 
      if (m_bmp == null || m_bmp.Width != this.Width || m_bmp.Height != this.Height) 
      { 
       m_bmp = new Bitmap(this.Width - m_scrollBarWidth, this.Height); 

       // TODO: Figure out why this is here. 
       m_scrollBar.Left = this.Width - m_scrollBarWidth; 
       m_scrollBar.Top = 0; 
       m_scrollBar.Width = m_scrollBarWidth; 
       m_scrollBar.Height = this.Height; 
      } 
     } 

Я надеюсь, что это помогает