使用paintcomponent在Jpanel上繪製矩形不起作用

Question

我想在DrawPanel上繪製矩形。這個矩形應該是一個對象。 當我添加它時，這個位置將是灰色的，但塗料組分不會畫，所以我什麼都看不到。

類Drawpanel.java將被添加到contentpane上，contentpane位於JFrame上。

import java.awt.event.*; 
import java.awt.*; 

import javax.swing.JPanel; 

public class DrawPanel extends JPanel implements MouseListener{ 

private static final long serialVersionUID = 6725416157621860479L; 

public DrawPanel() { 
    addMouseListener(this); 
    this.setLayout(null); 
    setPreferredSize(new Dimension(500, 500)); 
} 

Graphics2D g2d = null; 
@Override 
protected void paintComponent(Graphics g) { 
    // TODO Auto-generated method stub 
    super.paintComponent(g); 
    g2d = (Graphics2D)g; 
    System.out.println("paint!!!!!!!"); 
    for (int i = 0; i < 1500; i++) { 
     if (i %10 == 0) { 
      g2d.setColor(new Color(242, 242, 242)); 
      g2d.drawLine(0, i, 1500, i);// _ 
      g2d.drawLine(i, 0, i, 1500);// | 
     } 
    } 
    g2d.setColor(Color.BLUE); 
} 

@Override 
public void mouseClicked(MouseEvent arg0) { 
    if (START.modus != 4) { 
     return; 
    } 

    System.out.println("X_" + arg0.getX() + " | Y_"+arg0.getY()); 
    int x = (arg0.getX()) - (arg0.getX()%10); 
    int y = (arg0.getY()) - (arg0.getY()%10); 
    System.out.println("x_" + x + " " + "y_" + y); 
    Dia d = new Dia(x, y); 
    d.setBounds(x, y, 50, 50); 
    add(d); 
} 

@Override 
public void mouseEntered(MouseEvent arg0) { 
    // TODO Auto-generated method stub 
} 

@Override 
public void mouseExited(MouseEvent arg0) { 
    // TODO Auto-generated method stub 
} 

@Override 
public void mousePressed(MouseEvent arg0) { 
    // TODO Auto-generated method stub 
} 

@Override 
public void mouseReleased(MouseEvent arg0) { 
    // TODO Auto-generated method stub 
} 

} 

，不會被畫的對象是：

import java.awt.event.*; 
import java.awt.*; 

import javax.swing.*; 

public class Dia extends JPanel implements MouseListener { 

private Point startcoord; 
private int sizex = 50; 
private int sizey = 20; 

public Dia(int x, int y) { 
    super(); 
    addMouseListener(this); 
    this.startcoord = new Point(x, y); 
    setPreferredSize(new Dimension(sizex, sizey)); 
} 

@Override 
public void paintComponents(Graphics g) { 
    super.paintComponents(g); 
    System.out.println("Diaaaaa1"); 
    Graphics2D g2d = (Graphics2D) g; 
    g2d.drawLine(0, 0, 50, 50); 
    // g.setColor(Color.RED); 
    g.drawRect(0, 0, sizex, sizey); 
    g.setColor(Color.GREEN); 
    g.drawString("TEST", 3, 3); 
    System.out.println("Diaaaaa"); 
} 

public Point getStartcoord() { 
    return startcoord; 
} 

public void setStartcoord(Point startcoord) { 
    this.startcoord = startcoord; 
} 

@Override 
public void mouseClicked(MouseEvent e) { 
    System.out.println("diac"); 

} 

@Override 
public void mouseEntered(MouseEvent e) { 
    // TODO Auto-generated method stub 

} 

@Override 
public void mouseExited(MouseEvent e) { 
    // TODO Auto-generated method stub 

} 

@Override 
public void mousePressed(MouseEvent e) { 
    // TODO Auto-generated method stub 

} 

@Override 
public void mouseReleased(MouseEvent e) { 
    // TODO Auto-generated method stub 

} 

public static void main(String[] args) { 

    Dia c = new Dia(10, 10); 
    //c.textsize(); 
    JFrame a = new JFrame(); 
    a.setVisible(true); 
    a.setSize(new Dimension(100, 100)); 
    JPanel b = new JPanel(); 
    a.add(b); 
    b.add(c); 
} 


} 

當我開始主要在Dia類我什麼也看不見。爲什麼dia不會啓動paintcomponent方法？

Answer 1

真的很簡單，你重寫另一種方法paintComponents()但你需要paintComponent()。改變這一切，都將是工作。