在paintComponent方法中使用屬性

Question

我正在使用NetBeans GUI生成器，並試圖創建一種「Geogebra」。我對paintComponent的定義有問題。我想在我的組件中使用幾何圖形的數組列表，這是我的JFrame的一個屬性。但是，似乎java不識別數組列表。 這裏那裏的問題的部分代碼：

public GUI() { 
     initComponents(); 
    } 
     public List<Figure> Liste = new ArrayList<Figure>(); 

    /** 
    * This method is called from within the constructor to initialize the form. 
    * WARNING: Do NOT modify this code. The content of this method is always 
    * regenerated by the Form Editor. 
    */ 
    @SuppressWarnings("unchecked") 
    // <editor-fold defaultstate="collapsed" desc="Generated Code">       
    private void initComponents() { 

     jDialog1 = new javax.swing.JDialog(); 
     lblx = new javax.swing.JLabel(); 
     lbly = new javax.swing.JLabel(); 
     txtx = new javax.swing.JTextField(); 
     txty = new javax.swing.JTextField(); 
     btnOkPoint = new javax.swing.JButton(); 
     jDialog2 = new javax.swing.JDialog(); 
     jLabel1 = new javax.swing.JLabel(); 
     jLabel2 = new javax.swing.JLabel(); 
     lblx1 = new javax.swing.JLabel(); 
     lbly1 = new javax.swing.JLabel(); 
     lblx2 = new javax.swing.JLabel(); 
     lbly2 = new javax.swing.JLabel(); 
     txtx1 = new javax.swing.JTextField(); 
     txty1 = new javax.swing.JTextField(); 
     txtx2 = new javax.swing.JTextField(); 
     txty2 = new javax.swing.JTextField(); 
     btnoksegment = new javax.swing.JButton(); 
     MainPan = new javax.swing.JPanel(); 
     GraphPan = new javax.swing.JPanel(){ 
      @Override 
      public void paintComponent(Graphics g) { 

       for (int i = 0; i < this.Liste.size(); i++) { 
        if(this.Liste.get(i) instanceof Pts){ 
         Pts p = (Pts)this.Liste.get(i); 
         g.fillOval((int)Math.round(p.x),(int)Math.round(p.y), 10, 10); 
        } 
        if(this.Liste.get(i) instanceof Segment) { 
         Segment s = (Segment)this.Liste.get(i) ; 
         Segment s = (Segment) this.Liste.get(i); 
         g.drawLine(s.debut.x, s.debut.y, s.fin.x, s.fin.y); 
        } 
       } 
      } 
     }; 

Answer 1

this指匿名類，但主要的類包含成員變量。更換

Pts p = (Pts)this.liste.get(i); 

與

Pts p = (Pts)liste.get(i);