java - BasicButtonUI 按钮不会重绘

Question

我正在试验在 this SO post 上找到的代码关于使用 BasicButtonUI 制作的自定义按钮。我试图让我的自定义按钮在按下时淡出，但由于某种原因我看不到任何结果。我做了一个SSCCE来说明问题:

我在计时器中放了一条打印语句来验证它是否正常工作，让我相信我重绘的方式有问题。

import javax.swing.*;
import javax.swing.plaf.basic.BasicButtonUI;
import java.awt.*;
import java.awt.event.*;

class StyledButtonUI extends BasicButtonUI {

  @Override
  public void installUI (JComponent c) {
    super.installUI(c);
    AbstractButton button = (AbstractButton) c;
    button.setOpaque(false);
    button.setBorder(BorderFactory.createEmptyBorder (5, 15, 5, 15));
  }

  @Override
  public void paint (Graphics g, JComponent c) {
    AbstractButton b = (AbstractButton) c;
    paintBackground(g, b, b.getModel().isPressed () ? true : false);
    super.paint(g, c);
  }

  private void paintBackground (final Graphics g, final JComponent c, boolean fade) {
    final Dimension size = c.getSize();
    Graphics2D g2 = (Graphics2D) g;
    g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);

    //draws normal button
    g.setColor (c.getBackground ());
    g.fillRoundRect (0, 0, size.width, size.height - 5, 10, 10);

    if (fade) {
      Timer timer = new Timer (50, new ActionListener () {
        int i = 0;//starting opacity
        int limit = 15;//opacity limit

        public void actionPerformed (ActionEvent ae) {
          if (i <= limit) {
            System.out.println ("background color: " + c.getBackground () + " alpha: " + c.getBackground ().getAlpha () + " new fade in color: " + getAlphaColor (c.getBackground (), i) + " fade in alpha: " + i);
            g.setColor (getAlphaColor (c.getBackground (), i));
            g.fillRoundRect(0, 0, size.width, size.height - 5, 10, 10);
            i++;
          }
          else {
            ((Timer) ae.getSource ()).stop ();
          }
        }});

      timer.start ();
    }
  }

  private Color getAlphaColor (Color color, int newAlpha) {
    return new Color (color.getRed (), color.getGreen (), color.getBlue (), newAlpha);
  }

  public static void main (String[] args) {
    JFrame f = new JFrame("Button UI Test");
    f.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);

    JPanel p = new JPanel();
    p.setBackground(Color.WHITE);
    f.setContentPane(p);

    for (int i = 1; i <= 5; i++) {
      final JButton button = new JButton("Button #" + i);

      button.setBackground(Color.BLACK);
      button.setForeground(Color.WHITE);

      button.setUI(new StyledButtonUI());
      p.add(button);
    }

    f.pack();
    f.setLocation(500, 500);
    f.setVisible(true);
  }
}

Answer 1

不确定我是否会为此更改 UI。您绝对不应该在 painting() 方法中启动 Timer。您无法控制 Swing 何时确定组件需要重新绘制。例如，当您将鼠标移到按钮上时，它会重新绘制以实现翻转效果。

这是一个类的例子，当组件获得焦点时，它可以淡化任何组件的背景:

import java.awt.*;
import java.awt.event.*;
import java.util.Hashtable;
import java.util.ArrayList;
import javax.swing.*;

public class Fader
{
    //  background color when component has focus
    private Color fadeColor;

    //  steps to fade from original background to fade background
    private int steps;

    //  apply transition colors at this time interval
    private int interval;

    //  store transition colors from orginal background to fade background
    private Hashtable backgroundColors = new Hashtable();

    /*
     *  Fade from a background color to the specified color using
     *  the default of 10 steps at a 50 millisecond interval.
     *
     *  @param fadeColor the temporary background color
     */
    public Fader(Color fadeColor)
    {
        this(fadeColor, 10, 50);
    }

    /*
     *  Fade from a background color to the specified color in the
     *  specified number of steps at the default 5 millisecond interval.
     *
     *  @param fadeColor the temporary background color
     *  @param steps     the number of steps to fade in the color
     */
    public Fader(Color fadeColor, int steps)
    {
        this(fadeColor, steps, 50);
    }

    /*
     *  Fade from a background color to the specified color in the
     *  specified number of steps at the specified time interval.
     *
     *  @param fadeColor the temporary background color
     *  @param steps     the number of steps to fade in the color
     *  @param intevral  the interval to apply color fading
     */
    public Fader(Color fadeColor, int steps, int interval)
    {
        this.fadeColor = fadeColor;
        this.steps = steps;
        this.interval = interval;
    }

    /*
     *  Add a component to this fader.
     *
     *  The fade color will be applied when the component gains focus.
     *  The background color will be restored when the component loses focus.
     *
     *  @param component apply fading to this component
    */
    public Fader add(JComponent component)
    {
        //  Get colors to be used for fading

        ArrayList colors = getColors( component.getBackground() );

        //  FaderTimer will apply colors to the component

        new FaderTimer( colors, component, interval );

        return this;
    }

    /*
    **  Get the colors used to fade this background
    */
    private ArrayList getColors(Color background)
    {
        //  Check if the color ArrayList already exists

        Object o = backgroundColors.get( background );

        if (o != null)
        {
            return (ArrayList)o;
        }

        //  Doesn't exist, create fader colors for this background

        ArrayList colors = new ArrayList( steps + 1 );
        colors.add( background );

        int rDelta = ( background.getRed() - fadeColor.getRed() ) / steps;
        int gDelta = ( background.getGreen() - fadeColor.getGreen() ) / steps;
        int bDelta = ( background.getBlue() - fadeColor.getBlue() ) / steps;

        for (int i = 1; i < steps; i++)
        {
            int rValue = background.getRed() - (i * rDelta);
            int gValue = background.getGreen() - (i * gDelta);
            int bValue = background.getBlue() - (i * bDelta);

            colors.add( new Color(rValue, gValue, bValue) );
        }

        colors.add( fadeColor );
        backgroundColors.put(background, colors);

        return colors;
    }

    class FaderTimer implements FocusListener, ActionListener
    {
        private ArrayList colors;
        private JComponent component;
        private Timer timer;
        private int alpha;
        private int increment;

        FaderTimer(ArrayList colors, JComponent component, int interval)
        {
            this.colors = colors;
            this.component = component;
            component.addFocusListener( this );
            timer = new Timer(interval, this);
        }

        public void focusGained(FocusEvent e)
        {
            alpha = 0;
            increment = 1;
            timer.start();
        }

        public void focusLost(FocusEvent e)
        {
            alpha = steps;
            increment = -1;
            timer.start();
        }

        public void actionPerformed(ActionEvent e)
        {
            alpha += increment;

            component.setBackground( (Color)colors.get(alpha) );

            if (alpha == steps || alpha == 0)
                timer.stop();
        }
    }

    public static void main(String[] args)
    {
        // Create test components

        JComponent textField1 = new JTextField(10);
        textField1.setBackground( Color.YELLOW );
        JComponent textField3 = new JTextField(10);
        JComponent textField4 = new JTextField(10);
        JComponent button = new JButton("Start");
        JComponent checkBox = new JCheckBox("Check Box");

        JFrame frame = new JFrame("Fading Background");
        frame.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
        frame.getContentPane().add(textField1, BorderLayout.NORTH );
        frame.getContentPane().add(button, BorderLayout.SOUTH );
        frame.getContentPane().add(textField3, BorderLayout.WEST );
        frame.getContentPane().add(textField4, BorderLayout.EAST );
        frame.getContentPane().add(checkBox);

        //  Gradual Fading (using defaults)

//      Fader fader = new Fader( new Color(155, 255, 155) );
        Fader fader = new Fader( new Color(155, 255, 155), 10, 50 );
        fader.add( textField1 );
        fader.add( textField3 );
        fader.add( checkBox );

        //  Instant Fading

        fader = new Fader( new Color(255, 155, 155), 1, 1 );
        fader.add( textField4 );
        fader.add( button );

        frame.pack();
        frame.setVisible( true );
    }
}

您需要自定义它以支持在 mousePressed 上淡入淡出。