在TListView中将子项目图像居中 [英] Center subitem images in a TListView

问题描述

是否可以在 TListView 中修复子项目图像的绘制，以使它们不会被切除如图所示，在左侧？

Is it possible to fix the drawing of subitem images in a TListView so that they are not cut-off on the left hand side as shown in the image?

推荐答案

好吧， Pieter van Wyk ，我做了一个最小的示例，说明如何所有者绘制 TListView 组件以使图像居中在子项目中。

Well, Pieter van Wyk, I did minimal example of how you can owner-draw your TListView component in order to center images in sub-items.

答案已被重写。为了减小答案的大小，我删除了未使用和错误的部分。以前的版本可能在问题编辑的历史记录中找到。

下面的图片代表新代码的工作。

选定的行。


所选行上的图像周围带有白色。这不是错误-它是带有这种填充的源图像。

Picture below represents work of the new code.
One orange row is a selected row.
Images on selected row have white color around it. It is not a bug - it is a source image with such fill.

有一些代码可以执行与图片相同的操作：

There is the code that allows to do the same thing as on the picture:

procedure TForm1.ListView1DrawItem(Sender: TCustomListView; Item: TListItem; Rect: TRect;
  State: TOwnerDrawState);
var
  Bmp: TBitmap;
  Image: TBitmap;
  R: TRect;
  CenterH: Integer;
  CenterV: Integer;
  ImageIndex: Integer;
  ItemWidth: Integer;
  i: Integer;
begin
  // Set initial legth of point at the end of which image will be drawn.  
  // Column 0 is a "fixed" column
  ItemWidth := Sender.Column[0].Width;
  R := Rect;

  Bmp := TBitmap.Create;
  try
    Image := TBitmap.Create;
    try
      Bmp.SetSize(R.Width, R.Height);

      // Make fill for item
      if Item.Selected then
        Bmp.Canvas.Brush.Color := clWebOrange
      else
        Bmp.Canvas.Brush.Color := clMoneyGreen;
      Bmp.Canvas.FillRect(Bmp.Canvas.ClipRect);

      // Output image associated with 'fixed' column
      TListView(Sender).SmallImages.GetBitmap(Item.ImageIndex, Image);
      CenterH := (Sender.Column[0].Width - Image.Width) div 2;
      CenterV := (R.Height - Image.Height) div 2;
      Bmp.Canvas.Draw(CenterH, CenterV, Image);

      // Output text
      Bmp.Canvas.TextOut(CenterH + Image.Width + 6, 6, Item.Caption);

      // Draw sub-items
      for i:=0 to Item.SubItems.Count - 1 do
        begin
          // Obtain index of image
          ImageIndex := Item.SubItemImages[i];

          // Get associated image
          TListView(Sender).SmallImages.GetBitmap(ImageIndex, Image);

          // Center image
          CenterH := (Sender.Column[i+1].Width - Image.Width) div 2;
          CenterV := (R.Height - Image.Height) div 2;

          // Output image
          Bmp.Canvas.Draw(ItemWidth + CenterH, CenterV, Image);

          // Increase point where image started to be drawn
          Inc(ItemWidth, Sender.Column[i+1].Width);
        end;

      // Draw ready item's image onto sender's canvas
      Sender.Canvas.Draw(R.Left, R.Top, Bmp);
    finally
      Image.Free;
    end;
  finally
    Bmp.Free;
  end;
end;

要应用此代码，您必须激活 OwnerDraw 属性。

To apply this code you must activate OwnerDraw property.

请参阅此 TListView.OwnerDraw属性，该属性导致 docs.embarcadero 。我还想显示来自上面链接的报价：

See this TListView.OwnerDraw Property that leads to docs.embarcadero. I also would like to show a quote from a link above:

将OwnerDraw设置为true可以使列表视图接收OnDrawItem事件列表项的默认呈现方式。

Set OwnerDraw to true to allow the list view to receive the OnDrawItem event instead of the default rendering of list items.

PS

之后的列调整大小后，可能会出现一些图形伪像-只是尝试以隐藏（最小列大小）和显示图像（任何超出

P.S.
After column has been resized, there could be some graphical artifacts - just try to resize column in a way to hide (minimal possible size of column) and show image (any size of column that will exceeds size of associated image) and you will see what I meant.

PSS

绘制子项目的文本我把功课留给你;）

P.S.S.
Drawing a text of sub-items I leave to you as a homework ;)

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