如何在JFrame中

Question

應對公共無效paint（）方法

我的問題是，當我使用

public void paint(Graphics g) 
{} 

方法繪製一個String作爲

g.drawString("hello java",0,0); 

我完整的代碼

import javax.swing.*; 
import java.awt.*; 
class test 
extends JFrame 
{ 
public void testing() 
{ 
setSize(500,500); 
show(); 
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
} 
public void paint(Graphics g) 
{ super.paint(g); 
g.drawString("HELLO JAVA"); 
} 
public static void main(String arg[]) 
{ 
test t=new test(); 
t.testing(); 
} } 

在JFrame中，我得到一個黑色的屏幕沒有你好java被繪製 請幫我 預先感謝

Answer 1

要正確顯示繼承幀，在繼承的類塗料方法應該包含）super.paint的呼叫（：

class MyFrame extends JFrame { 

    public void paint(Graphics g) { 
     super.paint(g); 
     g.drawString("hello java", 50, 50); 
    } 

} 

編輯（在面板畫）：

import java.awt.*; 
import javax.swing.*; 

public class CustomPaint { 

    public static void main(String[] args) { 
     EventQueue.invokeLater(new Runnable() { 

      public void run() { 
       JFrame frame = new JFrame("CustomPaint"); 
       frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
       frame.add(new MyPanel()); 
       frame.pack(); 
       frame.setLocationByPlatform(true); 
       frame.setVisible(true); 
      } 
     }); 
    } 
} 

class MyPanel extends JPanel { 

    public Dimension getPreferredSize() { 
     return new Dimension(320, 240); 
    } 

    public void paintComponent(Graphics g) { 
     super.paintComponent(g); 
     Graphics2D g2 = (Graphics2D) g; 
     String msg = "HELLO JAVA"; 
     g2.setPaint(Color.BLUE); 
     int w = (getWidth() - g.getFontMetrics().stringWidth(msg))/2; 
     g2.drawString(msg, w, getHeight()/2); 
    } 
}