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stringGrid flickering issue

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Post time: 2020-3-13 20:00:01
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I have the following code in the drawcell event of stringGrid, which roughly means that every four rows alternately change the color,
Because there are many grids, when the scroll bar in the stringGrid changes, those grids flicker very much. How can I solve it?
code show as below:
var
  i, j: integer;
  rect: TRect;
begin
  with stringGrid do
  begin
    for i: = 1 to RowCount do
      for j: = 1 to ColCount do
      begin
        case ch of
          True: begin
                  Canvas.Brush.Color: = clSkyBlue; // ClBlue;
                  if (i mod 4 = 0) and (j = ColCount) then
                    if (i div 4) mod 2 = 0 then
                      ch: = False;
                end;
         False: begin
                 Canvas.Brush.Color: = clWindow;
                 if (i mod 4 = 0) and (j = ColCount) then
                   if (i div 4) mod 2 = 1 then
                   begin
                     ch: = True;
                   end;
            end;
         end;
            rect: = CellRect (j, i);
            Canvas.FillRect (rect);
            Canvas.font.color: = ClBlack;
            Canvas.TextOut (rect.left, rect.top, Cells [j, i]);
    end;
  end;
end;
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Post time: 2020-6-11 01:45:01
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There is a problem with your code. In the Drawcell event, it is the event triggered by drawing each cell.
Think about whether your code has failed!
Remove the loop, and directly use the parameters Arow and Acol to represent the currently drawn rows and columns,
Talk about your code problem,
1. Rect already has such a parameter in the event, how do you still define it above?
2. Remove from circulation
3. Draw the cell and write it like this. Change this sentence:
   Canvas.TextOut(rect.left, rect.top, Cells[j, i]);
   To:
   Canvas.TextRect(Rect,Rect.left,Rect.top,Cells[Acol,Arow]);
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Post time: 2020-6-12 15:15:01
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Save the color of each line, when you find the same, you don't need to redraw, just exit, so that it will not flicker.
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 Author| Post time: 2020-6-13 20:45:01
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stevevai:
   Because my stringGrid has 120 rows and 30 columns, but it can display up to 20 rows and 12 columns. The other rows and columns need to be moved by the scroll bar to see. But the maximum number of ACOL in this Drawcell is also the most displayable column. That is, 12 columns, with your method there will be no flickering phenomenon, but when moving the unit or scroll bar, those colors are displayed abnormally. So I came up with this stupid method. Can you help to solve it.
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Post time: 2020-6-14 15:15:01
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You put the refresh control in the scroll key and stop refreshing when you scroll. Try it
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 Author| Post time: 2020-6-16 08:00:01
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tonjmumu:

  But when I first loaded the form, there was already some flicker.
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Post time: 2020-6-16 10:30:01
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Arow can determine which row you are in, so no matter whether there is a scroll bar, you can use Arow to complete the function you need. I haven't encountered the problem you said, wait for me to test it for you,
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Post time: 2020-6-17 23:15:01
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I have encountered this problem:
But when moving the unit or scroll bar, those colors are displayed abnormally. You add the following code to the TopLeftChanged method of stringGrid:
    stringGrid.Enabled = false;
    stringGrid.Refresh;
    stringGrid.Enabled = true;
    stringGrid.SetFocus;
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Post time: 2020-6-18 21:30:01
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The Drawcell of stringGrid only draws the displayed part. When the cell or scroll bar is moved, the stringGrid draws the previously displayed part, so the color is not normal. The TopLeftChanged event can be triggered when the cell or scroll bar is moved, and the refresh is forced in the TopLeftChanged event. Can be solved.
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Post time: 2020-6-19 00:30:01
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After the test, this is a problem with your code algorithm. Let me show you my code:
with self.StringGrid1 do
     begin
          if ((Arow div 4) mod 2)=0 then
             canvas.Brush.Color:=clSkyBlue
          else
             canvas.Brush.Color:=clred;// ClBlue;

          Canvas.font.color:=Clblue;
          Canvas.TextRect(Rect,Rect.left,Rect.top,Cells[Acol,Arow]);
     end;
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