Question

java 如何让以下代码画图流畅，而不是断断续续，因双缓冲没学，尽量在以下代码基础上该把，求大师指点

//设计如下GUI，在JFrame元件中鼠标拖拽的轨迹可以写文字打草稿
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class Test extends JFrame{
private Container c;
private JLabel label;
private MyPaint myPaint;
public Test(){
super("草稿面板");
label=new JLabel("草稿面板",JLabel.CENTER); //文本居中
c=getContentPane();
myPaint=new MyPaint();
label.setFont(new Font("Serif",Font.BOLD,22)); //设置组件文字大小
c.setLayout(new BorderLayout());
c.add(label,BorderLayout.NORTH);
c.add(myPaint,BorderLayout.CENTER);
setBounds(200,200,500,500);
setVisible(true);
}
public static void main(String args[]){
Test app=new Test();
app.addWindowListener(new MyWindowListener());
}
}
class MyPaint extends JPanel{
private int x=0,y=0;
private int nx=0,ny=0;
private Point startPoint=new Point(x,y);
private Point endPoint=new Point(nx,ny);
public MyPaint(){
addMouseMotionListener(new MyMouseMotionListener());
addMouseListener(new MyMouseListener());
}
public void paint(Graphics g){
//super.paint(g); 添加后画面会重绘
//g.drawLine((int)startPoint.getX(),(int)startPoint.getY(),(int)endPoint.getX(),(int)endPoint.getY()); 画线
g.fillRect((int)startPoint.getX(),(int)startPoint.getY(),5,5);
}
//拖拽侦听
class MyMouseMotionListener extends MouseMotionAdapter{
public void mouseDragged(MouseEvent e){
startPoint=e.getPoint();
repaint();
}
public void mouseMoved(MouseEvent e){
}
}
//鼠标单击侦听
class MyMouseListener extends MouseAdapter{
public void mousePressed(MouseEvent e){
startPoint=e.getPoint();
repaint();
}
public void mouseReleased(MouseEvent e){
endPoint=e.getPoint();
repaint();
}
}
}
左图为教材，右图为我的代码，画快了感觉侦听跟不上来，不知道什么原因。

Answer 1

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

public class DrawDemo extends JFrame
{
	private Container c;
	private JLabel label;
	private MyPaint myPaint;
	
	public DrawDemo()
	{
		super("草稿面板");
		label = new JLabel("草稿面板", JLabel.CENTER); // 文本居中
		c = getContentPane();
		myPaint = new MyPaint();
		label.setFont(new Font("Serif", Font.BOLD, 22)); // 设置组件文字大小
		c.setLayout(new BorderLayout());
		c.add(label, BorderLayout.NORTH);
		c.add(myPaint, BorderLayout.CENTER);
		setBounds(200, 200, 500, 500);
		setVisible(true);
	}
	
	public static void main(String args[])
	{
		DrawDemo app = new DrawDemo();
	}
}

class MyPaint extends JPanel
{
	private int x = 0, y = 0;
	private int nx = 0, ny = 0;
	private Point startPoint = new Point(x, y);
	private Point endPoint = new Point(nx, ny);
	
	public MyPaint()
	{
		addMouseMotionListener(new MyMouseMotionListener());
		addMouseListener(new MyMouseListener());
	}
	
	public void paint(Graphics g)
	{
		g.drawLine((int) startPoint.getX(), (int) startPoint.getY(), (int) endPoint.getX(), (int) endPoint.getY());
		startPoint = endPoint;
	}
	
	// 拖拽侦听
	class MyMouseMotionListener extends MouseMotionAdapter
	{
		public void mouseDragged(MouseEvent e)
		{
			endPoint = e.getPoint();
			repaint();
		}
		
		public void mouseMoved(MouseEvent e)
		{
			endPoint = e.getPoint();
		}
	}
	
	// 鼠标单击侦听
	class MyMouseListener extends MouseAdapter
	{
		public void mousePressed(MouseEvent e)
		{
			startPoint = e.getPoint();
		}
	}
}