How does listview know, which column is the mouse click?

woshibate

Thank you!

woshibate

listview is of type vsReport

snoopyhai

Column's Index can know which one you ordered

woshibate

How does this work?

ListView.Column ??

ListView.Selected.Column ??

Or in which event?

jk66255

Look at what the foreigner wrote.

Extended GetItemAt

This method (GetItemAt) only provides the information about which ListItem (if any) is located at the specified coordinates passed as parameters, but only works with the first column of the TListView. The rest are ignored. If we needed to know if the user clicked on an element in another column, we can declare a new method in a derived class:

uses ComCtrls;

type
  TListViewX = class (TListView)
  public
    function GetItemAtX (X, Y: integer; var Col: integer): TListItem;
  end;

implementation

function TListViewX.GetItemAtX (X, Y: integer;
    var Col: integer): TListItem;
var
  i, n, RelativeX, ColStartX: Integer;
  ListItem: TlistItem;
begin
  Result: = GetItemAt (X, Y);
  if Result <> nil then begin
    Col: = 0; // First column
  end else if (ViewStyle = vsReport)
      and (TopItem <> nil) then begin
    // First, let's try to find the row
    ListItem: = GetItemAt (TopItem.Position.X, Y);
    if ListItem <> nil then begin
      // Now let's try to find the Column
      RelativeX: = X-ListItem.Position.X-BorderWidth;
      ColStartX: = Columns [0] .Width;
      n: = Columns.Count-1;
      for i: = 1 to n do begin
        if RelativeX <ColStartX then break;
        if RelativeX <= ColStartX +
            StringWidth (ListItem.SubItems [i-1]) then
        begin
          Result: = ListItem;
          Col: = i;
          break;
        end; // if
        Inc (ColStartX, Columns [i] .Width);
      end; // for
    end; // if
  end; // if
end;

Casting to the new class

We don't need to intall this new component and register it in the components palette as we explained in another article. Instead, any time we want to access this method, we can just cast the object (for example ListView1) to our new class . For example in a MouseDown event:

procedure TForm1.ListView1MouseDown (Sender: TObject;
  Button: TMouseButton; Shift: TShiftState; X, Y: Integer);
var
  col: integer;
  li: TListItem;
begin
  li: = TListViewX (ListView1) .GetItemAtX (x, y, col);
  if li <> nil then
    ShowMessage ('Column #' + IntToStr (col));
end;

woshibate

Not quite right, some can, some can't

woshibate

Most of them are in column 0

jk66255

Modified:
function TListViewX.GetItemAtX (X, Y: integer;
  var Col: integer): TListItem;
var
  i, n, RelativeX, ColStartX: Integer;
  ListItem: TlistItem;
  OldRowSelect: Boolean;
  Found: Boolean;
begin
  Result: = GetItemAt (X, Y);
  if (not RowSelect) and (Result <> nil) then
  begin
    Col: = 0; // First column
  end
  else if (ViewStyle = vsReport)
    and (TopItem <> nil) then
  begin
    // First, let's try to find the row
    // ListItem: = GetItemAt (TopItem.Position.X, Y);

    // save rowselect setting
    OldRowSelect: = RowSelect;
    RowSelect: = True;
    ListItem: = GetItemAt (X, Y);
    // Restore rowselect setting;
    RowSelect: = OldRowSelect;

    if ListItem <> nil then
    begin
      // Now let's try to find the Column
      RelativeX: = X-ListItem.Position.X-BorderWidth;
// ColStartX: = Columns [0] .Width;
      ColStartX: = 0;
      n: = Columns.Count-1;
      for i: = 0 to n do
      begin
        if RelativeX <ColStartX + Columns [i] .Width then
        begin
          Result: = ListItem;
          Col: = i;
          break;
        end;
{if RelativeX <= ColStartX +
          StringWidth (ListItem.SubItems [i-1]) then
        begin
          Result: = ListItem;
          Col: = i;
          break;
        end; // if}
        Inc (ColStartX, Columns [i] .Width);
      end; // for
// Col: = i;
    end; // if
  end; // if
end;

snoopyhai

In the cloumnonclick event of Listview, cloumn can be used directly

You only need to use its cloumn.index to know which one you ordered

chenfnu

listview.Selected is fine