怎么在一个JButton上画一个三角形

Question

用什么方法都可以 
我最想看的是重写paintComponent
谢谢

Answer 1

import javax.swing.*;
import java.awt.event.*;
import java.awt.*;class Mypane extends JPanel implements ActionListener
{
   JButton rect,ovel,regl;   int count=0;
   JPanel Mypane2;   public Mypane()
   {
       rect = new JButton("矩形");
       ovel = new JButton("椭圆");
       regl = new JButton("三角形");             //--------Mypane1----------
         JPanel Mypane1=new JPanel();
         Mypane1.add(rect); 
      Mypane1.add(ovel); 
         Mypane1.add(regl);     
         //--------Mypane2-------------    
       Mypane2=new JPanel();
       Mypane2.setLayout(new GridLayout(3,3));
                        
        //-------------------------
        this.setLayout(new BorderLayout());
        
        add(Mypane1,BorderLayout.NORTH);
        add(Mypane2,BorderLayout.CENTER);
        //------------------------------
        rect.addActionListener(this);
        ovel.addActionListener(this);
        regl.addActionListener(this);
       }    
  public void actionPerformed(ActionEvent e)
  {
      
    Triangle tt=new Triangle();
    Rectangl rr=new Rectangl();
    ellipse ee =new ellipse(); 
    
      if(e.getSource() == regl  && count < 9)
        {
          Mypane2.add(tt);
          count++;
          Mypane2.updateUI();
       }
           if(e.getSource() == ovel  && count < 9)
        {
          Mypane2.add(rr);
          count++;          Mypane2.updateUI();//更新图形界面
       }
       if(e.getSource() == rect  && count < 9)
        {
          Mypane2.add(ee);
          count++;
          Mypane2.updateUI();
       }  
  } 
  
  
    public static void main(String args[])
  {
     JFrame Myframe=new JFrame("");    
        Myframe.getContentPane().add(new Mypane());
        Myframe.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        Myframe.setSize(300,300);
        Myframe.setVisible(true);
            
            
  }
  
class Triangle extends JPanel 
{   public void paintComponent(Graphics g)
  {   
        Polygon p=new Polygon();
        p.addPoint(0,20);
         p.addPoint(40,0);
         p.addPoint(40,40);
         g.setColor(Color.red);
        g.fillPolygon(p);    
      }}
class Rectangl extends JPanel 
{
 
 
   public void paintComponent(Graphics g)
  { 
    g.setColor(Color.green);
       g.fillRect(20,20,40,40);
  }
  
  }
class ellipse extends JPanel 
{
  
  
  
   public void paintComponent(Graphics g)
  {
        g.setColor(Color.blue);
       g.fillOval(20,20,40,40);
  }    }    
}

Answer 2

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;class Kao extends JFrame implements ActionListener{
    JPanel btpl=new JPanel(); 
    JPanel tuply=new JPanel();    
    JPanel p[]=new JPanel[9]; 
    JButton b1=new JButton("圆");
    JButton b2=new JButton("角");
    JButton b3=new JButton("方");
    int y=0;
    public static void main(String args[]){
        Kao tu=new Kao();
        tu.setVisible(true);
    }
    Kao(){
        setTitle("Draw");setSize(300,350);
        Container con=getContentPane();
        con.add(btpl,BorderLayout.NORTH);
        btpl.add(b1);btpl.add(b2);btpl.add(b3);    
        con.add(tuply,BorderLayout.CENTER);
            tuply.setLayout(new GridLayout(3,3));
              for(int a=0;a<9;a++){
                  p[a]=new JPanel();
                  tuply.add(p[a]);
              }              
        b1.addActionListener(this);
        b2.addActionListener(this);
        b3.addActionListener(this);
    }
class Py extends JPanel{
    public Py(){
        super.setSize(100,80);
    }
    public void paintComponent(Graphics g){
        g.setColor(new Color(16,45,150));
        g.fillOval(20,10,60,60);
    }
}
class Pj extends JPanel{
    public Pj(){
        super.setSize(100,80);
    }
    public void paintComponent(Graphics g){
        g.setColor(new Color(150,16,45));
        int px[]={50,20,80};int py[]={10,70,70};
        g.fillPolygon(px,py,3);
    }
}        
class Pf extends JPanel{
    public Pf(){
        super.setSize(100,80);
    }
    public void paintComponent(Graphics g){
        g.setColor(new Color(45,150,16));
        g.fillRect(20,10,60,60);
    }
}
    public void actionPerformed(ActionEvent e){
        y++;
        if(y<=9){
           if(e.getActionCommand()=="圆"){
                 p[y-1].add(new Py());repaint();
           }
           if(e.getActionCommand()=="角"){
                 p[y-1].add(new Pj());repaint();
           }    
           if(e.getActionCommand()=="方"){
                 p[y-1].add(new Pf());repaint();
           }       
        }
     }    
}

Answer 3

class PicButton extends JButton
{
private BufferedImage image_over; //鼠标在按钮上的图片
private BufferedImage image_off; //鼠标不在按钮上的图片
private BufferedImage image_pressed; //鼠标按下时的图片

private int buttonWidth; //宽
private int buttonHeight; //高
private int[] pixels; //储存图片数据的数组，用于计算contains
private boolean mouseOn;
private boolean mousePressed;

public PicButton()
{
mouseOn = false;
mousePressed = false;
//加载图片
image_over = loadImage("button2.png");
image_off = loadImage("button.png");
image_pressed = loadImage("button3.png");

buttonWidth = image_off.getWidth();
buttonHeight = image_off.getHeight();

//读取图片数据
pixels = new int[buttonWidth * buttonHeight];
//抓取像素数据
PixelGrabber pg = new PixelGrabber(image_off, 0, 0, buttonWidth,
buttonHeight, pixels,
0, buttonWidth);
try{
pg.grabPixels();
}
catch(Exception e)
{
e.printStackTrace();
}

//必须设置！否则会有残影！
this.setOpaque(false);

this.setPreferredSize(new Dimension(buttonWidth, buttonHeight));
this.addMouseMotionListener(new MouseMotionHandler());
this.addMouseListener(new MouseHandler());
}

//读取图片文件
public BufferedImage loadImage(String filename)
{
File file = new File(filename);

if(!file.exists())
return null;

try{
return ImageIO.read(file);
}
catch(IOException e)
{
e.printStackTrace();
return null;
}
}

//覆盖此方法绘制自定义的图片
public void paintComponent(Graphics g)
{
g.drawImage(image_off, 0, 0, this);
if(mouseOn)
g.drawImage(image_over, 0, 0, this);
else if(mousePressed)
g.drawImage(image_pressed, 0, 0, this);
}

//覆盖此方法绘制自定义的边框
public void paintBorder(Graphics g)
{
//不填则不要边框
}

public boolean contains(int x, int y)
{
//不判定的话会越界，在组件之外也会激发这个方法
if(!super.contains(x, y))
return false;

int alpha = (pixels[(buttonWidth * y + x)] >> 24) & 0xff; repaint();
if(alpha == 0)
{
return false;
}
else
{
return true;
}
}

//暂时没啥用，留着
class MouseMotionHandler extends MouseMotionAdapter
{
public void mouseMoved(MouseEvent e)
{
//mouseOn = true;
// repaint();
} }

//处理进入，离开图片范围的消息
class MouseHandler extends MouseAdapter
{
public void mouseExited(MouseEvent e)
{
mouseOn = false;
repaint();
}
public void mouseEntered(MouseEvent e)
{
mouseOn = true;
repaint();
}
public void mousePressed(MouseEvent e)
{
mouseOn = false;
mousePressed = true;
repaint();
}
public void mouseReleased(MouseEvent e)
{
//防止在按钮之外的地方松开鼠标
if(contains(e.getX(), e.getY()))
mouseOn = true;
else
mouseOn = false;

mousePressed = false;
repaint();
}
}
}

Answer 4

自己画个图片 然后button设置下icon就可以了吧