java中Swing中的自定義JButton

package Swing;
import java.awt.AlphaComposite;  
import java.awt.Color;  
import java.awt.Dimension;  
import java.awt.FlowLayout;
import java.awt.Font;  
import java.awt.GradientPaint;  
import java.awt.Graphics;  
import java.awt.Graphics2D;  
import java.awt.Point;  
import java.awt.RenderingHints;  
import java.awt.Shape;  
import java.awt.event.MouseAdapter;  
import java.awt.event.MouseEvent;  
import java.awt.geom.Arc2D;  
import java.awt.geom.GeneralPath;  
import java.awt.geom.RoundRectangle2D;  
  
import javax.swing.JButton;  
import javax.swing.JFrame;
  
/** 
 * Custom JButton 
 *  
 * @version 0.1.0 
 * @author ruislan <a href="mailto:[email protected]" mce_href="mailto:[email protected]"></a> 
 */  
public class RButton extends JButton {  
    private static final long serialVersionUID = 39082560987930759L;  
    public static final Color BUTTON_COLOR1 = new Color(205, 255, 205);  
    public static final Color BUTTON_COLOR2 = new Color(51, 154, 47);  
    // public static final Color BUTTON_COLOR1 = new Color(125, 161, 237);  
    // public static final Color BUTTON_COLOR2 = new Color(91, 118, 173);  
    public static final Color BUTTON_FOREGROUND_COLOR = Color.WHITE;  
    private boolean hover;  
    private int style;  
    public static final int ROUND_RECT = 0;     // 分別定義的四種形狀
    public static final int LEFT_ROUND_RECT = 1;  
    public static final int RIGHT_ROUND_RECT = 2;  
    public static final int BALL = 3;  
    public static final int STAR = 4;  
  
    public RButton() {  
        this(ROUND_RECT);  
    }  
  
    public RButton(int style) 
    {  
        this.style = style;  
        setPreferredSize(new Dimension(60, 30));   //默認初始的大小爲60、30
        if (BALL == style) 
        {  
            setPreferredSize(new Dimension(42, 42));      //爲球形時新大小
        } else if (STAR == style) 
        {  
            setPreferredSize(new Dimension(42, 42));     //爲星星時新大小
        }  
        setFont(new Font("system", Font.PLAIN, 12));  
        setBorderPainted(false);  
        setForeground(BUTTON_COLOR2);  
        setFocusPainted(false);  
        setContentAreaFilled(false);  
        addMouseListener(new MouseAdapter() {  
            @Override  
            public void mouseEntered(MouseEvent e) {                           //鼠標進入button
                setForeground(BUTTON_FOREGROUND_COLOR);  
                hover = true;  
                repaint();  
            }  
  
            @Override  
            public void mouseExited(MouseEvent e) {                //鼠標離開button
                setForeground(BUTTON_COLOR2);  
                hover = false;  
                repaint();  
            }  
        });  
    }  
  
    @Override  
    protected void paintComponent(Graphics g) {  
        Graphics2D g2d = (Graphics2D) g.create();  
        int h = getHeight();  
        System.out.println(h);
        
        int w = getWidth();
        System.out.println(w);
        float tran = 1F;  
        if (!hover) 
        {  
            tran = 0.3F;  
        }  
  
        g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING,  
                RenderingHints.VALUE_ANTIALIAS_ON);  
        GradientPaint p1;  
        GradientPaint p2;  
        if (getModel().isPressed()) 
        {  
            p1 = new GradientPaint(0, 0, new Color(0, 0, 0), 0, h - 1,  
                    new Color(100, 100, 100));  
            p2 = new GradientPaint(0, 1, new Color(0, 0, 0, 50), 0, h - 3,  
                    new Color(255, 255, 255, 100));  
        } 
        else 
        {  
            p1 = new GradientPaint(0, 0, new Color(100, 100, 100), 0, h - 1,  
                    new Color(0, 0, 0));  
            p2 = new GradientPaint(0, 1, new Color(255, 255, 255, 100), 0,  
                    h - 3, new Color(0, 0, 0, 50));  
        }  
        g2d.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER,  
                tran));  
        GradientPaint gp = new GradientPaint(0.0F, 0.0F, BUTTON_COLOR1, 0.0F,  
                h, BUTTON_COLOR2, true);  
        g2d.setPaint(gp);  
        switch (style) {  
        case ROUND_RECT: {  
            RoundRectangle2D.Float r2d = new RoundRectangle2D.Float(0, 0,  
                    w - 1, h - 1, 20, 20);  
            Shape clip = g2d.getClip();  
            g2d.clip(r2d);  
            g2d.fillRect(0, 0, w, h);  
            g2d.setClip(clip);  
            g2d.setPaint(p1);  
            g2d.drawRoundRect(0, 0, w - 1, h - 1, 20, 20);  
            g2d.setPaint(p2);  
            g2d.drawRoundRect(1, 1, w - 3, h - 3, 18, 18);  
            break;  
        }  
        case LEFT_ROUND_RECT: {  
            RoundRectangle2D.Float r2d = new RoundRectangle2D.Float(0, 0,  
                    (w - 1) + 20, h - 1, 20, 20);  
            Shape clip = g2d.getClip();  
            g2d.clip(r2d);  
            g2d.fillRect(0, 0, w, h);  
            g2d.setClip(clip);  
            g2d.setPaint(p1);  
            g2d.drawRoundRect(0, 0, (w - 1) + 20, h - 1, 20, 20);  
            g2d.setPaint(p2);  
            g2d.drawRoundRect(1, 1, (w - 3) + 20, h - 3, 18, 18);  
            g2d.setPaint(p1);  
            g2d.drawLine(w - 1, 1, w - 1, h);  
            g2d.setPaint(p2);  
            g2d.drawLine(w - 2, 2, w - 2, h - 1);  
            break;  
        }  
        case RIGHT_ROUND_RECT: {  
            RoundRectangle2D.Float r2d = new RoundRectangle2D.Float(-20, 0,  
                    (w - 1) + 20, h - 1, 20, 20);  
            Shape clip = g2d.getClip();  
            g2d.clip(r2d);  
            g2d.fillRect(0, 0, w, h);  
            g2d.setClip(clip);  
            g2d.setPaint(p1);  
            g2d.drawRoundRect(-20, 0, (w - 1) + 20, h - 1, 20, 20);  
            g2d.setPaint(p2);  
            g2d.drawRoundRect(-19, 1, (w - 3) + 20, h - 3, 18, 18);  
            g2d.setPaint(p1);  
            g2d.drawLine(0, 1, 0, h);  
            g2d.setPaint(p2);  
            g2d.drawLine(1, 2, 1, h - 1);  
            break;  
        }  
        case BALL: {  
            Arc2D.Float a2d = new Arc2D.Float(0, 0, w, h, 0, 360, Arc2D.CHORD);  
            Shape clip = g2d.getClip();  
            g2d.clip(a2d);  
            g2d.fillRect(0, 0, w, h);  
            g2d.setClip(clip);  
            g2d.setPaint(p1);  
            g2d.drawOval(0, 0, w - 1, h - 1);  
            g2d.setPaint(p2);  
            g2d.drawOval(1, 1, w - 3, h - 3);  
            break;  
        }  
        case STAR: {  
            int x = w / 2;  
            int y = h / 2;  
            int r = w / 2;  
            // 計算五個頂點  
            Point[] ps = new Point[5];  
            for (int i = 0; i <= 4; i++) {  
                ps[i] = new Point((int) (x - r  
                        * Math.sin((i * 72 + 36) * 2 * Math.PI / 360)),  
                        (int) (y + r  
                                * Math.cos((i * 72 + 36) * 2 * Math.PI / 360)));  
            }  
            GeneralPath star = new GeneralPath();  
            star.moveTo(ps[3].x, ps[3].y);  
            star.lineTo(ps[0].x, ps[0].y);  
            star.lineTo(ps[2].x, ps[2].y);  
            star.lineTo(ps[4].x, ps[4].y);  
            star.lineTo(ps[1].x, ps[1].y);  
            star.lineTo(ps[3].x, ps[3].y);  
            star.closePath();  
            Shape clip = g2d.getClip();  
            g2d.clip(star);  
            g2d.fillRect(0, 0, w, h);  
            g2d.setClip(clip);  
            g2d.setPaint(p1);  
            g2d.draw(star);  
            g2d.setPaint(p2);  
            g2d.draw(star);  
            break;  
        }  
        default:  
            break;  
        }  
        g2d.dispose();  
        super.paintComponent(g);  
    }  
    public static void main(String[] args)
  {
 JButton button=new RButton(0);//產生一個圓形按鈕
 button.setText("開始");
 button.setBackground(new Color(216,191,216));//設置背景色爲綠色
 //產生一個框架顯示這個按鈕
 JFrame frame=new JFrame("圖形按鈕");
 frame.getContentPane().setBackground(Color.orange);
 frame.getContentPane().setLayout(new FlowLayout());
 frame.getContentPane().add(button);
 frame.setSize(200,250);
 frame.setVisible(true);
 frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
} 

結果：

注意代碼中的幾個部分：

首先是paintComponent方法中最後一行，我們調用了父類的paintComponent方法，這是因爲我們要靠父類來繪製字符，但是父類的這個方法除了繪製字符之外還會繪製其他的，所以我們需要關閉掉其他的（當然我們也可以自己來繪製字符，但是JButton提供了方法爲什麼不用呢），所以我們在構造方法那裏調用了：
setBorderPainted(false);
setFocusPainted(false);
setContentAreaFilled(false);
告訴父類不用繪製邊框，不用繪製焦點，不用繪製內容部分，這部分我們自己來搞*o*。

然後就是這一句了g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON)告訴繪製API我們需要平滑一點，否則繪製出來會有很多鋸齒喲。

接下來的這一句g2d.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER,tran))告訴繪圖API我們需要繪製一個有透明度的，tran就是透明度（0-1）。

然後就是將邊框的邊角變直角爲圓角，我們繪製一個RoundRectangle2D，這個就是邊角都爲圓角的方形，然後我們根據這個方形來clip我們的方形，這樣方形就被RoundRectangle2D的圓角方形包裹，從而變成了圓角方形。

最後就是繪製外邊線和內邊線，通過改變內邊線和外邊線的色變從而造成陷入或者突出效果。

整個JButton改造完畢，如果你能夠活用clip的話，你也可以做一個五角星的JButton喲。