如何获取DBGrid单元格的屏幕坐标 [英] How do I get screen coordinates of the DBGrid cell

问题描述

我想在当前行的特定单元格的右下角显示弹出式按钮或花哨的信息（彩色背景等）。

I want to show popup button or fancy message (with coloured background, etc) just under right-bottom corner of particular cell of the current row.

现在我只想到如何获得网格坐标：

x = DBGrid.DataSource.DataSet.RecNo

y = DBGrid .Columns [index]

For now I only figured how to get grid coordinates:
x = DBGrid.DataSource.DataSet.RecNo
y = DBGrid.Columns[index]

还有TCustomGrid.CellRect，它会做我想要的，但它受到保护，我不想继承和创建另一个组件类

There is also TCustomGrid.CellRect, which would do what I want, but it's protected and I don't want to inherit and create another component class.

我可以想到的一个疯狂的解决方法是将onDrawColumnCell事件中的TRect保存到某个数组。

One crazy workaround I can think of is to save TRect-s in onDrawColumnCell event to some array.

那么你觉得怎么样？

编辑

如何获取第二个单元格的屏幕坐标在当前行？

EDIT
How do I get screen coordinates of, say, second cell in the current row ?

推荐答案

您可以使用一点欺骗获取当前的单元格坐标。 ：）

You can get the current cell coordinates, using a little deception. :)

允许组件的后台访问祖先类的受保护字段。因为除了获得 CellRect 方法 TDBGrid 之外，我们不需要做任何事情，我们将创建一个插件（无任何后代），只允许我们访问该受保护的方法。然后，我们可以将 TDBGrid 键入新的后代类，并使用它来达到受保护的方法。我使用 THACK 作为前缀命名后裔，以明确说明后裔的唯一目的是获得（hack）祖先类。

Descendants of a component are allowed to access the protected fields of the ancestor class. Since we don't need to do anything except gain access to the protected CellRect method of TDBGrid, we'll create an interposer (do-nothing descendant) that simply allows us access to that protected method. We can then typecast the TDBGrid to that new descendant class and use it to reach the protected method. I name the descendant using THack as a prefix to make it clear that the only purpose of the descendant is to gain access ("hack") the ancestor class.

// implementation
type
  THackDBGrid=class(TDBGrid);

// Where you need the coordinates
var
  CurrRow: Integer;
  Rect: TRect;
begin
  CurrRow := THackDBGrid(DBGrid1).Row;
  Rect := THackDBGrid(DBGrid1).CellRect(ColIndexYouWant, CurrRow);
  // Rect now contains the screen coordinates you need, or an empty
  // rectangle if there is no cell at the col and row specified.
end;

正如OP在评论中指出的那样，在 delphi.about.com 。

As the OP has indicated in a comment, there's a more detailed description of how this works at delphi.about.com.

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