import java.awt.*; import javax.swing.*; import java.awt.event.*; public class HuaTu implements MouseMotionListener,ActionListener{ static final int r=3; static int ox, oy; static int flag=1; public static void main(String arg[]){ JFrame f=new JFrame("Paint"); Container p=f.getContentPane(); p.setLayout(new FlowLayout()); JButton jButton1 = new JButton("红"); JButton jButton2 = new JButton("黑"); JButton jButton3 = new JButton("退出"); //Graphics g.setColor(new Color(255,0,0)); //ButtonEvent arg=new ButtonEvent(arg); jButton1.addActionListener(new HuaTu()); jButton2.addActionListener(new HuaTu()); jButton3.addActionListener(new HuaTu()); p.addMouseMotionListener(new HuaTu()); p.add(jButton1); p.add(jButton2); p.add(jButton3); f.setSize(200,200); f.show(); } public void actionPerformed(ActionEvent e){ if(e.getActionCommand().equals("红")){ flag=1; } else if (e.getActionCommand().equals("黑")){ flag=2; } else if (e.getActionCommand().equals("退出")) System.exit(0); } public void mouseDragged(MouseEvent e){ Container c=(Container)e.getSource(); Graphics g=c.getGraphics(); if (ox>=0) { if(flag==1){ g.setColor(new Color(168,0,255)); g.drawLine(ox,oy,e.getX(),e.getY());} else { g.setColor(new Color(0,0,0)); g.drawLine(ox,oy,e.getX(),e.getY());} } ox=e.getX();oy=e.getY(); } public void mouseMoved(MouseEvent e){ ox=-1;oy=-1; } } 
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