[求助]请问paintComponent要怎么用?

JComponet中的paintComponent要怎么用呢?感觉好象和paint差不多,但------: import java.awt.*; import javax.swing.*; class Mycanvas extends JPanel{ public void paintComponet(Graphics g){ super.paintComponent(g); g.setColor(Color.red); g.drawString("a JPanle used as canvas",50,50); } } public class Apt extends JApplet{ Mycanvas canvas; JPanel panel; JButton button; public void init(){ canvas=new Mycanvas();panel=new JPanel(); button=new JButton("ok"); canvas.setVisible(true); panel.add(button);Container con=getContentPane(); con.add(panel,BorderLayout.NORTH); con.add(canvas,BorderLayout.CENTER); } } 书上的例子,结果看起来和这个方法并没什么关系... 文档上写的: Calls the UI delegate's paint method, if the UI delegate is non-null. We pass the delegate a copy of the Graphics object to protect..... 似乎也没写清楚用法,反正是没看明白...
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//一段小程序 供参考。。。 import java.awt.*; import java.awt.event.*; import javax.swing.*;

public class ShowColors2 extends JFrame {

private JButton changeColorButton; private Color color = Color.LIGHT_GRAY; private Container container;

public ShowColors2(){ super(" Using JColorChooser "); container = getContentPane(); container.setLayout( new FlowLayout()); changeColorButton = new JButton ("Change Color "); changeColorButton.addActionListener(new ActionListener () { public void actionPerformed(ActionEvent event ){ color = JColorChooser.showDialog(ShowColors2.this, "Choose a color ", color);

if (color == null) color = Color.LIGHT_GRAY; container.setBackground(color);

} }) ; container.add( changeColorButton ); setSize(400,130); setVisible(true);

}

public static void main (String args[] ){ ShowColors2 application = new ShowColors2(); application.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE ); } }

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

public class LinesRectsOvals extends JFrame { public LinesRectsOvals(){ super("Drawing lines , rectangles ans ovals "); setSize(400,165); setVisible(true);

} public void paint (Graphics g){ super.paint(g); g.setColor(Color.RED); g.drawLine(5,30,350,30); g.setColor(Color.BLUE); g.drawRect(5,40,90,55); g.fillRect(100,40,90,50);

g.setColor(Color.CYAN); g.fillRoundRect(195,40,90,55,50,50); g.drawRoundRect(290,40,90,55,20,20);

g.setColor(Color.YELLOW); g.draw3DRect(5,100,90,55,true); g.fill3DRect(100,100,90,55,false); g.setColor( Color.MAGENTA); g.drawOval( 195,100,90,55); g.fillOval(290,100,90,55); }

public static void main(String args[]){ LinesRectsOvals application = new LinesRectsOvals(); application.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE );

} }

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呵呵。。眼花了。。看错了。。。
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