Home > Delphi > How to Select a “Bar” in the TChart Delphi control

How to Select a “Bar” in the TChart Delphi control

Reference : http://delphi.about.com/od/adptips2006/qt/chart_selectbar.htm

Tip submitted by Meze Calin Nicolae

Here’s a method of simulating a selection in the TChart Delphi control. When a user clicks on a bar of a chart, the respective bar changes its color.

Everything is being done using one event, the onClickSeries, which provides us the index of the clicked bar.

Follow the steps:

  • Drop a TChart (“Additional” tab) control on a Delphi form.
  • Add one (empty) series to the Chart.
  • Select a “Bar” chart style.

Declare two form level variables:

colors : array of TColor;
k : integer;

Fill in the Chart with some “dummy” data in the Form’s OnCreate event:

procedure TChartForm.FormCreate(Sender: TObject) ;
begin
  SetLength(colors,7) ;
  for k := 0 to 6 do colors[k] := clBlue;

  Chart1.Series[0].Add(10,’test2′,Colors[0]) ;
  Chart1.Series[0].Add(70,’test3′,Colors[1]) ;
  Chart1.Series[0].Add(90,’test4′,Colors[2]) ;
  Chart1.Series[0].Add(40,’test5′,Colors[3]) ;
  Chart1.Series[0].Add(66,’test6′,Colors[4]) ;
end;

Handle the OnClickSeries event as:

procedure TChartForm.Chart1ClickSeries(
  Sender: TCustomChart;
  Series: TChartSeries;
  ValueIndex: Integer;
  Button: TMouseButton;
  Shift: TShiftState;
  X, Y: Integer) ;
begin
  for k := 0 to 6 do
  if k <> ValueIndex then
    colors[k] := clBlue
  else
    colors[k] := clRed;

  Chart1.Series[0].Clear;
  Chart1.Series[0].Add(10,’test2′,Colors[0]) ;
  Chart1.Series[0].Add(70,’test3′,Colors[1]) ;
  Chart1.Series[0].Add(90,’test4′,Colors[2]) ;
  Chart1.Series[0].Add(40,’test5′,Colors[3]) ;
  Chart1.Series[0].Add(66,’test6′,Colors[4]) ;
end;

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