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Thread: Problem with paintComponent...?

  1. #1
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    Default Problem with paintComponent...?

    Hello !
    Here is my Code:
    LineDrawV2
    import java.awt.Color;
    import java.awt.Graphics;
    import java.awt.event.ActionEvent;
    import java.awt.event.ActionListener;
    import java.io.File;
    import java.io.FileNotFoundException;
    import java.util.Scanner;
    import java.util.logging.Level;
    import java.util.logging.Logger;
    import javax.swing.*;
    import javax.swing.filechooser.FileNameExtensionFilter;
     
    public abstract class LineDrawV2 extends JFrame implements ActionListener{
        public static int i = 0;
        public static Double[] storeCoordinates;
        public static JFrame frame1 = new JFrame();
     
        private static final long serialVersionUID = 1L;
        private static Graphics Graphics;
     
        public static void main(String[] args)  {
            try {
                UIManager.setLookAndFeel("com.sun.java.swing.plaf.windows.WindowsLookAndFeel");
            } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                Logger.getLogger(LineDrawV2.class.getName()).log(Level.SEVERE, null, ex);
            } 
     
     
            frame1.setSize(800, 600);
            frame1.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            frame1.setLocationRelativeTo(null);
            frame1.setTitle("Line Draw 2");
            //frame1.getContentPane().setLayout(null);
     
     
     
            final JFileChooser martin = new JFileChooser();
            martin.setAcceptAllFileFilterUsed(false);
            martin.setFileFilter(new FileNameExtensionFilter("Text Files", "txt", "rtf"));
     
     
     
            JMenuBar mb = new JMenuBar();
            frame1.setJMenuBar(mb);
            JMenu filemb = new JMenu("File");
            mb.add(filemb);
            JMenuItem importmb = new JMenuItem("Import");
            filemb.add(importmb);
            JMenuItem exitmb = new JMenuItem("Exit");
            filemb.add(exitmb);
     
            exitmb.addActionListener(new ActionListener() {
     
                public void actionPerformed(ActionEvent e)
                {
     
                    System.exit(0);
     
                }
            }); 
     
            importmb.addActionListener(new ActionListener() {
     
                public void actionPerformed(ActionEvent e)
                {
                    try {
                        martin.showOpenDialog(frame1);
                        File selectedFile = martin.getSelectedFile();
     
                        String sexy = selectedFile + "";
                        System.out.println(sexy);
     
                        File file = new File(sexy);
     
                        Scanner martin2 = new Scanner(file);
     
                        int numLines = 0;
                        i = 0;
     
                        while(martin2.hasNext()){
     
                            martin2.nextLine();
                            numLines++;
                            }
     
                        martin2 = new Scanner(file);
     
                        String[] lines = new String[numLines];
                        while(martin2.hasNext()){
     
                            lines[i] = martin2.nextLine();
                            System.out.println(lines[i]);
                            i++;
                        }
                        String active;
                        storeCoordinates = new Double[i*4];
                        int k = i;
                        int q1 = 0;
                        while(k>0){
                            active = lines[i-k];
     
                            int q = 0;
                            String morph = "";
                            while(q<active.length()){
                                if(active.charAt(q) != ','){
                                morph = morph + active.charAt(q);
                                }
                                if(q+1 == active.length() || active.charAt(q) == ','){
     
                                    Double dedomraz = Double.valueOf(morph);
                                    storeCoordinates[q1] = dedomraz;
                                    morph = "";
                                    q1++;
                                }
     
                            q++;
     
                            }
     
                            k--;
                        }
     
                        drawing();
     
     
     
     
     
                    } catch (FileNotFoundException ex) {
                        Logger.getLogger(LineDrawV2.class.getName()).log(Level.SEVERE, null, ex);
                    }
     
                }
            }); 
     
     
            frame1.setVisible(true);
     
     
        }
     
        public static void drawing(){
            DrawingPanel panel = new DrawingPanel();
            frame1.add(panel);
        }
     
    }

    DrawingPanel
    import java.awt.Color;
    import java.awt.Graphics;
    import java.awt.event.ActionEvent;
    import javax.swing.JPanel;
    import java.lang.Math;
    public class DrawingPanel extends JPanel {
        private static final long serialVersionUID = 1L;
     
        public void paintComponent(Graphics g){
            LineDrawV2 LDV2 = new LineDrawV2() {
     
                @Override
                public void actionPerformed(ActionEvent e) {
                    throw new UnsupportedOperationException("Not supported yet.");
                }
            };
     
            super.paintComponents(g);
            g.setColor(Color.BLACK);
            g.drawLine(15, 15, 100, 100);
     
     
        }
     
    }

    so now the problem is that g.drawLine doesn't appear anywhere. I found out if I put drawing(); out of the action listener the line will appear but I need the Line to be drawn after or in the action listener because in the future I will need some numbers from a file that will give the line coordinates (this is just a example line so you can help me just to make it appear...).

    Thanks in advance

    P.S. It's a messy code but I hope you don't mind...


  2. #2
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    Default Re: Problem with paintComponent...?

    Problems:
    • You shouldn't be creating a new LineDrawV2 object inside of DrawingPanel's paintComponent(...) method. Why do you feel that your program needs this?
    • You know that code like this risks a nasty NPE error if you declared DrawingPanel inside of LineDrawV2.
    • LineDrawV2 should not be abstract. I believe that you're trying to fix an error the wrong way by making it abstract. The correct solution is to have the class implement all necessary interface methods.
    • LineDrawV2 shouldn't extend JFrame or implement any interfaces.
    • You shouldn't have any static variables as that only confuses things and makes your program non-OOPs compliant.
    • After adding DrawingPanel to the JFrame, the JFrame should be packed.
    • You call setVisible(true) on the JFrame *after* adding all components, including LineDraw, not before.
    • ... and many more problems.

  3. The Following User Says Thank You to Fubarable For This Useful Post:

    *mT (July 12th, 2012)

  4. #3
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    Default Re: Problem with paintComponent...?

    packing the frame really helped ! Thank You

    and one more question
    Quote Originally Posted by Fubarable View Post
    Problems:
    • You know that code like this risks a nasty NPE error if you declared DrawingPanel inside of LineDrawV2.
    I'm confused, how can I add the DrawingPanel in the frame if I don't declare it ?

  5. #4
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    Default Re: Problem with paintComponent...?

    I may have gotten that backwards: you may get an exception, perhaps stackoverflow exception if you define a new LineDrawV2 inside of DrawingPanel's paintComponent. Bottom line is you don't want to create components or add components in the paint or paintComponent method.

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