swing - How can I draw lines, rectangles, and circles in my Java paint program? -

i'm working on paint program 1 of classes , i'm stuck. part of code (separated 3 java classes). when click on button "ligne", want able draw line in white rectangle. sorry french comments.

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//cree une fenetre     public class question   {       public static void main(string[] args)       {           paint_gui test2 = new paint_gui();       }   }  

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import java.awt.*;   import javax.swing.*;    //class contenant le code pour dessiner   public class paint_dessin extends jpanel {      public void paintcomponent(graphics g)      {         super.paintcomponent(g);        setbackground(color.white);        g.setcolor(color.black);      }      public void tracerligne()     {        system.out.println("ligne");     }   }    

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import javax.swing.*;   import java.awt.event.*;   import java.awt.*;    public class paint_gui extends jframe   {       //panels contenant tout les bouton de mon interface       private jpanel panelbtn;        //bar d'outil btn       private jbutton btntracerligne;      //object paint_dessin      private paint_dessin espacedessin = new paint_dessin();       public paint_gui()       {           final int window_width = 650;           final int window_height = 450;            setsize (window_width, window_height);           settitle("paint v.2.0");           setdefaultcloseoperation(jframe.exit_on_close);           setlayout(new borderlayout());            // appeler la methode qui construit la barre de btn.           buildpanelbtn();           add(panelbtn, borderlayout.north);             add(espacedessin, borderlayout.center);            // afficher la fenetre.          setvisible(true);    }     private void buildpanelbtn()    {        btntracerligne = new jbutton("ligne");        btntracerligne.addactionlistener(new lignelistener());         // creer le panel.        panelbtn = new jpanel();        // ajouter les composantes au label        panelbtn.add(btntracerligne);   }   private class lignelistener implements actionlistener   {      public void actionperformed(actionevent e)      {         espacedessin.tracerligne();      }   }   

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you're current code has problem in you're creating new paint_dessin in lignelistener class's actionperformed method, , while object created same class paint_dessin object displayed in jframe, different object , calling methods on have absolutely no effect on paint_dessin displayed. need declare private paint_dessin variable once in paint_gui class, class field, initialize variable either @ declaration or in paint_gui constructor, , display object in gui , call methods on gui in listener class. e.g.,

public class paint_gui extends jframe   {       private jpanel panelbtn;       private jbutton btntracerligne;       private paint_dessin espacedessin = new paint_dessin();      public paint_gui()       {           final int window_width = 650;           //... code deleted sake of brevity          // paint_dessin espacedessin = new paint_dessin();           add(espacedessin, borderlayout.center);            // afficher la fenetre.          setvisible(true);    }     private void buildpanelbtn()    {        // ....  }    private class lignelistener implements actionlistener   {      public void actionperformed(actionevent e)      {       // paint_dessin tracerligne = new paint_dessin();       // tracerligne.tracerligne();       espacedessin.tracerligne(); // call method on same object!    }   }