java - 获取 jlabel 内文本的边界

Question

我想绘制一个从 JLabel 中的文本到 JLabel 外部的点的箭头。为了在适当的位置开始箭头，我需要 JLabel 内实际文本的边界。我下面的回答将展示如何获得这些界限。

Answer 1

您可以使用SwingUtilities.layoutCompoundLabel

import java.awt.*;
import javax.swing.*;
import javax.swing.border.*;

public class LabelLayout extends JLabel
{
    @Override
    protected void paintComponent(Graphics g)
    {
        super.paintComponent(g);

        Graphics grid = g.create();
        grid.setColor( Color.ORANGE );

        Rectangle viewR = new Rectangle();
        viewR.width = getSize().width;
        viewR.height = getSize().height;
        Rectangle iconR = new Rectangle();
        Rectangle textR = new Rectangle();

        String clippedText = SwingUtilities.layoutCompoundLabel
        (
            this,
            grid.getFontMetrics(),
            getText(),
            getIcon(),
            getVerticalAlignment(),
            getHorizontalAlignment(),
            getVerticalTextPosition(),
            getHorizontalTextPosition(),
            viewR,
            iconR,
            textR,
            getIconTextGap()
        );

        int gridSize = 10;
        int start = iconR.x;
        int end = iconR.x + iconR.width;

        System.out.println("Text bounds: " + textR );
        System.out.println("Icon bounds: " + iconR );

        for (int i = start; i < end; i += gridSize)
        {
            grid.drawLine(i, iconR.y, i, iconR.y + iconR.height);
        }

        grid.dispose();
    }

    private static void createAndShowGUI()
    {
        LabelLayout label = new LabelLayout();
        label.setBorder( new LineBorder(Color.RED) );
        label.setText( "Some Text" );
        label.setIcon( new ImageIcon( "DukeWaveRed.gif" ) );
        label.setVerticalAlignment( JLabel.CENTER );
        label.setHorizontalAlignment( JLabel.CENTER );
//      label.setVerticalTextPosition( JLabel.BOTTOM );
        label.setVerticalTextPosition( JLabel.TOP );
        label.setHorizontalTextPosition( JLabel.CENTER );

        JFrame frame = new JFrame("SSCCE");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.add( label );
        frame.setLocationByPlatform( true );
        frame.pack();
        frame.setSize(300, 200);
        frame.setVisible( true );
    }

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

此示例在标签中的图标上方绘制额外的线条。