用鼠标在面板上拖拽，画不同颜色的线条 - JAVA论坛

得分:0

// try it
import java.util.Vector;
import java.awt.*;
import java.awt.Color;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;

public class Myframe1 extends JFrame
{
  Mypanel1 p1;
  Mypanel2 p2;
  public Color c=Color.white;
  public Myframe1(String str)
  {
    super(str);
    p2=new Mypanel2();
    p1=new Mypanel1(p2);

    this.getContentPane().setLayout(new BorderLayout());
    this.getContentPane().add(p1,BorderLayout.NORTH);
    this.getContentPane().add(p2,BorderLayout.CENTER);
    setDefaultCloseOperation(EXIT_ON_CLOSE);
    setSize(600,500);
    setVisible(true);
  }
  public static void main(String args[])
  {
    new Myframe1("画图");
  }
}

class Mypanel1 extends JPanel implements ActionListener
{
  JButton b1,b2,b3,b4,b5;
  public Color c;
  final Mypanel2 p2;
  public Mypanel1(Mypanel2 p2)
  {
    this.p2=p2;
    b1=new JButton("红色");
    b2=new JButton("蓝色");
    b3=new JButton("绿色");
    b4=new JButton("橡皮");
    b5=new JButton("清除");
    this.add(b1);
    this.add(b2);
    this.add(b3);
    this.add(b4);
    this.add(b5);
    b1.addActionListener(this);
    b2.addActionListener(this);
    b3.addActionListener(this);
    b4.addActionListener(this);
    b5.addActionListener(this);
  }
  public void actionPerformed(ActionEvent e)
  {
    if(e.getSource()==b1)
    {
      p2.setCurrentColor(Color.red);
      p2.setMode(Mypanel2.RED);
    }
    else if(e.getSource()==b2)
    {
      p2.setCurrentColor(Color.blue);
      p2.setMode(Mypanel2.BLUE);
    }
    else if(e.getSource()==b3)
    {
      p2.setCurrentColor(Color.green);
      p2.setMode(Mypanel2.GREEN);
    }
    else if(e.getSource()==b4)
    {
      p2.setCurrentColor(Color.white);
      p2.setMode(Mypanel2.RUBBER);
    }
    else
    {
      p2.setCurrentColor(Color.white);
      p2.setMode(Mypanel2.ERASE);
    }
    p2.repaint();
  }
}

class Mypanel2 extends JPanel implements MouseMotionListener
{
  public final static int RED     = 0;
  public final static int BLUE    = 1;
  public final static int GREEN   = 2;
  public final static int RUBBER  = 3;
  public final static int ERASE   = 4;
  public final static int NOTHING = 5;
  int mode = NOTHING;
  public Color c;
  Vector rects = new Vector();
  int x = 0;
  int y = 0;
  final int w = 9;
  final int h = 9;
  public Mypanel2()
  {
    c = Color.white;
    setBackground(c);
    this.addMouseMotionListener(this);
  }
  public void paintComponent(Graphics g)
  {
    g.setColor(c);
    super.paintComponent(g);
    switch(mode)
    {
      case RED:
      case BLUE:
      case GREEN:
        setBackground(c);
        break;
      case RUBBER:
        for(int i = 0; i<rects.size(); i++)
        {
          Rectangle rect = (Rectangle) rects.elementAt(i);
          int x = rect.x;
          int y = rect.y;
          int w = rect.width;
          int h = rect.height;
          g.fillOval(x,y,w,h);
        }
        break;
      case ERASE:
        rects.clear();
        setBackground(c);
        break;
      case NOTHING:
        setBackground(c);
        break;
    }
  }
  public void setCurrentColor(Color currentC)
  {
    this.c = currentC;
  }
  public void setMode(int mode)
  {
    this.mode = mode;
  }
  public void mouseDragged(MouseEvent e)
  {
    if(mode == RUBBER)
    {
      x = e.getX();
      y = e.getY();
      Rectangle rect = new Rectangle(x,y,w,h);
      rects.add(rect);
      repaint();
    }
  }
  public void mouseMoved(MouseEvent e){}
}

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