mypanel.java

这是一个swing的练习

package lab9Package;
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.awt.geom.*;

public class MyPanel extends JPanel 
	implements ActionListener{
	public JButton blueButton = new JButton("blue");
	public JButton redButton = new JButton("red");
	public Color color;
	
	public void paintComponent(Graphics g)
	{
		super.paintComponent(g);
		Graphics2D g1 = (Graphics2D)g;
		//add Button
		add(blueButton);
		add(redButton);
		setLayout(new FlowLayout());
		//add ActionListener
		blueButton.addActionListener(this);
		redButton.addActionListener(this);
		
		//draw a ellipse
		Ellipse2D ellipse = new Ellipse2D.Double(100,100,50,50);
		g1.setPaint(color);
		g1.fill(ellipse);
	}
	
	public void actionPerformed(ActionEvent e)
	{
		Object o = e.getSource();
		if(o == blueButton)
		{
			color = Color.BLUE;
			//updateUI();
			repaint();
		}
		if(o == redButton)
		{
			color = Color.RED;
			//updateUI();
			repaint();
		}
	}
}