Java Swing图不显示

Question

I'm trying to read a CSV file and plot a graph based on it. However, when the frame shows up, it is empty. Any idea where I am going wrong?

import java.awt.Graphics;
import java.awt.Polygon;
import java.awt.Color;
import javax.swing.*;
import java.io.*;
import java.util.Scanner;


public class Poly extends JPanel
{
 int time[]=new int[10000];
 int generated[]=new int[10000];

public void paintComponent( Graphics g )
{
    super.paintComponent( g ); 
    // Draw a Polygone
    //int xValues[] = { 20, 40, 50, 30, 20, 15 };
    //int yValues[] = { 50, 50, 60, 80, 80, 60 };
    //Polygon polygon1 = new Polygon( xValues, yValues, 6 );
    //g.drawPolygon( polygon1 );                            
    // Draw a Polyline
    //int xValues2[] = { 70, 90, 100, 80, 70, 65, 60 };
    //int yValues2[] = { 100, 100, 110, 110, 130, 110, 90 };
    g.setColor(Color.RED);
    g.drawPolyline( time, generated, 10000 );              
}

public void run()
{
    String csvFile = "VaryHarvesterSize_VaryEnergyBufferMax_InputFile(64050KPIT2011_AllYear.dat.keep).csv";
    String line = "";
    String cvsSplitBy = ",";
    int k=0;

    try
    {
        File summaryFile=new File(csvFile);
        Scanner reader = new Scanner(summaryFile);
        reader.nextLine();

        //System.out.println(reader.nextLine());
        while(k<10000)
        {
            // use comma as separator
            line = reader.nextLine();
            String[] record = line.split(cvsSplitBy);
            double temp=Double.parseDouble(record[0].trim());
    time[k]=(int)temp;
            temp = Double.parseDouble(record[3].trim());
    generated[k]=(int)temp;
            //System.out.println(record);
            //System.out.println("Time="+time[k]+" Energy="+generated[k]);
            k++;

        }
    }

    catch(Exception e)
    {

        e.printStackTrace();
    }



}


public static void main (String[] args)
{
    Poly obj=new Poly();
    obj.run();


    JFrame frame=new JFrame("Polygone And Polyline")   ;
    JPanel policePanel=new Poly();
    frame.add(policePanel);
    frame.setSize(400,400);
    frame.setDefaultCloseOperation(frame.EXIT_ON_CLOSE);
    frame.setVisible(true);
}
}

I tried with hard coded values, it shows up on the frame. But the values in the file don't.

Answer 1

JPanel policePanel=new Poly();
    frame.add(policePanel);

Here you are adding a new panel to the frame. However you have called run on another instance of Poly before this. That means the data is being populated in another instance which you haven't added to the frame. Instead call 'run' on this instance and it should work.