如何将JPanel绘制为Nimbus JButton？

Question

在Nimbus的外观和感觉JButtons有一个非常整洁和准确的外观,圆形边框和漂亮的背景.
我想渲染一个具有相同外观的JPanel(显然它不会有按下状态等).
我有什么选择？

Answer 1

在JPanel上获取"按钮外观"的最简单方法可能是扩展JPanel和覆盖paintComponent.

这是Nimbus的JButton外观:

这是我在a上的类似外观的实现JPanel(我添加了一个空边框来显示这个例子,并且角落不是半透明的):

这是我的代码(使用渐变):

public class ColorDemo extends JPanel {

    private final int gradientSize = 18;
    private final Color lighterColor = new Color(250, 250, 250);
    private final Color darkerColor = new Color(225, 225, 230);
    private final Color edgeColor = new Color(140, 145, 145);
    private final Stroke edgeStroke = new BasicStroke(1);
    private final GradientPaint upperGradient = new GradientPaint(
            0, 0, lighterColor,
            0, gradientSize, darkerColor);


    @Override
    public void paintComponent(Graphics g) {
        Graphics2D g2 = (Graphics2D)g;
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, 
                            RenderingHints.VALUE_ANTIALIAS_ON);
        GradientPaint lowerGradient = new GradientPaint(
                0, getHeight()-gradientSize-1, darkerColor,
                0, getHeight(), lighterColor);
        g2.setPaint(upperGradient);
        g2.fillRect(0, 0, getWidth()-1 , gradientSize);
        g2.setPaint(darkerColor);
        g2.fillRect(0, gradientSize, getWidth()-1, getHeight()-gradientSize-1);
        g2.setPaint(lowerGradient);
        g2.fillRect(0, getHeight()-gradientSize, getWidth()-1, getHeight()-1);
        g2.setStroke(edgeStroke);
        g2.setPaint(edgeColor);
        g2.drawRoundRect(0, 0, getWidth()-1, getHeight()-1,
                               gradientSize/2, gradientSize/2);
    }
}

UPDATE

这是AgostinoX的一种改进paintComponent方法,它解决了我的代码中的角点问题.

    @Override
    public void paintComponent(Graphics g) {

        Graphics2D g2 = (Graphics2D) g;
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                            RenderingHints.VALUE_ANTIALI??AS_ON);
        float gradientPerc = (float)gradientSize/getHeight();
        LinearGradientPaint lgp = new LinearGradientPaint(0,0,0,getHeight()-1,
           new float[] {0, gradientPerc, 1-gradientPerc, 1f},
           new Color[] {lighterColor, darkerColor, darkerColor, lighterColor});
        g2.setPaint(lgp);
        g.fillRoundRect(0, 0, getWidth()-1, getHeight()-1,
            gradientSize, gradientSize);
        g2.setColor(edgeColor);
        g2.setStroke(edgeStroke);
        g.drawRoundRect(0, 0, getWidth()-1, getHeight()-1,
            gradientSize, gradientSize);
    }

另请参阅我对如何隐藏JScrollBar中箭头按钮的答案,了解如何自定义Nimbus的外观.并查看颜色和画家的Nimbus默认值.