更改JButton焦点区域 [英] Change JButton focus area

问题描述

如何更改JButton的焦点区域，以便当我将光标悬停在按钮上时，在将光标悬停在实际按钮本身上之前，我的服装翻转图标不会被激活.

How do i change the area of focus on a JButton so that when i hover my cursor over the button my costume rollover Icon isn't activated slightly before my cursor is over the actual button itself.

推荐答案

按钮的contains(x, y)方法确定鼠标何时进入按钮.如果您的自定义按钮不是矩形，则需要覆盖此方法.

The contains(x, y) method of the button determines when the mouse enters the button. If your custom button is not rectangular then you would need to override this method.

这是一个演示此概念的旧示例:

Here is an old example that demonstrates this concept:

// Old example code found on the internet somewhere
// to paint a Round button with hit detection

import java.awt.*;
import java.awt.event.*;
import java.awt.geom.*;
import javax.swing.*;

public class RoundButton extends JButton
{
    public RoundButton(String label)
    {
        super(label);

        // These statements enlarge the button so that it
        // becomes a circle rather than an oval.
        Dimension size = getPreferredSize();
        size.width = size.height = Math.max(size.width, size.height);
        setPreferredSize(size);
        setSize(size);

        // This call causes the JButton not to paint the background.
        // This allows us to paint a round background.
        setContentAreaFilled(false);
    }

    // Paint the round background and label.
    protected void paintComponent(Graphics g)
    {
        if (getModel().isArmed()) {
                // You might want to make the highlight color
                // a property of the RoundButton class.
                g.setColor(Color.lightGray);
            } else {
                g.setColor(getBackground());
            }
        g.fillOval(0, 0, getSize().width-1, getSize().height-1);

            // This call will paint the label and the focus rectangle.
        super.paintComponent(g);
    }

    // Paint the border of the button using a simple stroke.
    protected void paintBorder(Graphics g)
    {
        g.setColor(getForeground());
        g.drawOval(0, 0, getSize().width-1, getSize().height-1);
    }

    // Hit detection.
    Shape shape;

    public boolean contains(int x, int y)
    {
        // If the button has changed size, make a new shape object.
        if (shape == null || !shape.getBounds().equals(getBounds())) {
            shape = new Ellipse2D.Float(0, 0, getWidth(), getHeight());
        }
        return shape.contains(x, y);
    }

    private static void createAndShowUI()
    {
        // Create buttons that overlap one another

        JButton button = new RoundButton("Jackpot");
        button.setBackground(Color.green);
        button.setLocation(0, 0);

        JButton button2 = new RoundButton("Jackpot2");
        button2.setBackground(Color.red);
        button2.setLocation(40, 40);

        // Create a frame in which to show the button.
        JFrame frame = new JFrame("Round Button");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().setBackground(Color.yellow);
        frame.setLayout(null);
        frame.add(button);
        frame.add(button2);
        //frame.setLayout(new FlowLayout());
        frame.setLocationByPlatform( true );
        frame.setSize(250, 200);
        frame.setVisible(true);

        MouseListener mouseListener = new MouseAdapter()
        {
            public void mouseEntered( MouseEvent e ) {}

            public void mouseExited( MouseEvent e ) {}

            public void mouseClicked( MouseEvent e )
            {
                System.out.println( "clicked " );
            }

            public void mousePressed( MouseEvent e )
            {
                System.out.println( "pressed " );
            }

            public void mouseReleased( MouseEvent e )
            {
                System.out.println( "released " );
            }
        };

        button.addMouseListener( mouseListener );
    }

    public static void main(String[] args)
    {
        EventQueue.invokeLater(new Runnable()
        {
            public void run()
            {
                createAndShowUI();
            }
        });
    }
}

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