如何在执行时更新图表中的数据（在C ++构建器中）？

Question

I'm using Borland C++ Builder to create this. The code is very simple because its only purpose, for now, is to help me learn how to use the TChart functions. I'll use what I learn to create a more complex program later.

I have a series of numbers that must be shown on a memo box and on a chart. The values in the chart are displayed after the program finishes its exectuion, however, I need the values to be updated in real time - I mean, everytime the program calculates a new number, it must be immediately show on the chart. Is it possible to do that? If so, how can I do it?

Thanks in advance.

#pragma hdrstop
#include "Unit1.h"
//---------------------------------------------------------------------------
#pragma package(smart_init)
#pragma resource "*.dfm"
TForm1 *Form1;
//---------------------------------------------------------------------------
__fastcall TForm1::TForm1(TComponent* Owner)
    : TForm(Owner)
{
}
//---------------------------------------------------------------------------

void __fastcall TForm1::Button1Click(TObject *Sender)
{

   TChartSeries* series1 = Chart1->Series[0];
   series1->Clear();

   int num = 0;

   Memo1->Clear();

     for(int i=0; i<5000; i++)
     {
            num = num++;
            Memo1->Lines->Add(IntToStr(num));
            series1->AddXY(i, num, "", clGreen);

           }
   }

Answer 1

You should force a chart repaint whenever you want:

Chart1->Repaint();

So you could have:

void __fastcall TForm1::Button1Click(TObject *Sender)
{
    TChartSeries* series1 = Chart1->Series[0];
    series1->Clear();

    int num = 0;

    Memo1->Clear();

    for(int i=0; i<5000; i++)
    {
        num = num++;
        Memo1->Lines->Add(IntToStr(num));
        series1->AddXY(i, num, "", clGreen);
        Chart1->Repaint();
    }
}

Or, to improve the performance, you could force a chart repaint after adding some values instead of after each addition. Ie:

void __fastcall TForm1::Button1Click(TObject *Sender)
{
    TChartSeries* series1 = Chart1->Series[0];
    series1->Clear();

    int num = 0;

    Memo1->Clear();

    for(int i=0; i<5000; i++)
    {
        num = num++;
        Memo1->Lines->Add(IntToStr(num));
        series1->AddXY(i, num, "", clGreen);

        if (i % 100 == 0) {
            Chart1->Repaint();
        }
    }
}

Answer 2

Yes, this is an old thread but I have a suggestion for anyone else who runs across it. You can also repaint just the series which maybe requires less overhead than repainting the entire chart. To do that use the TChartSeries repaint method. For the given example then you would put a "series1->Repaint();" somewhere, inside the for loop I guess.